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Hybrid materials consisting of aniline (ANI) and/or 2‐aminodiphenylamine (PD) in the presence of V2O5 nanoparticles were synthesized by in‐situ chemical oxidative polymerization in one‐step. Physicochemical and electrochemical characterization confirmed that in the structure of the composites, intercalation between the polymer chains and the V2O5 slabs occurs. Optical properties study shows that the optical band gap of poly(ANI‐co‐PD)/V2O5 is lower than poly‐PD/V2O5. Thermal stability of the composites by thermogravimetric analysis was evaluated. Composites showed electrochemical activity with improved electron‐transfer of the redox species in the polymer observed by cyclic voltammetry. These results highlight the great influence of the V2O5 sheets and the polymer composition on the hybrid materials formation and properties. The authors wish to acknowledge the directorate General of Scientific Research and Technological Development (DGRSDT) (Algeria). Financial support from the Spanish Ministerio de Ciencia e Innovación (PID2019-105923RB-I00) is gratefully acknowledged. A.F.Q.J. gratefully acknowledges Generalitat Valenciana for the financial support through Santiago Grisolía grant (GRISOLIA/2016/084).

This paper describes the synthesis and properties of a new nitro-substituted bidentate Schiff base ligand (HL) and its nickel complex (Ni(II)-2L). Its ligand was derived from the condensation of 2′-methoxyphenyl-2-ethylamine with 5-nitro-2-hydroxybenzaldehyde. This ligand and its nickel complex were characterized through elemental analysis, UV–Vis, IR, 1H NMR and 13C NMR. The molecular structure of the nickel complex was confirmed using single-crystal X-ray diffraction. This complex crystallizes in dichloromethane in triclinic system, space group of P-1 with a = 6.6803 (2), b = 9.6702 (2), c = 12.1836 (3) and 1 formula unit in the cell. The obtained data revealed that the Ni(II) center is tetra-coordinated by two oxygen and two nitrogen atoms involving two ligands. Cyclic voltammograms of the nickel complex, recorded in DMF solutions, showed one quasi-reversible redox couple related to the Ni(II)/Ni(I) couple, demonstrating its electro-activity. This indicates a slow redox transition and/or electron exchange process, which implies that this electrochemical process is mainly diffusion-controlled. The antioxidant activity of the synthesized compounds was evaluated from the reactivity with the free radical DPPH, showing IC50 values between 0.4 and 4.5 mg/mL. The authors thank the Algerian Ministry of Higher Education and Scientific Research (MESRS) and the Directorate General of Scientific Research and Technological Development (DGRSDT) for their financial support. The authors also gratefully acknowledge the financial help (MAT2016-76595-R) of the Ministerio de Economía y Competitividad and FEDER. Special thanks are owed to the Spanish Ministry of Economy and Competitiveness (MINECO) for the granting of a “Ramón y Cajal” contract (RYC-2017-23618).

Large-scale environmental applications of microbial electrochemical technologies (MET), such as wastewater treatment, bioremediation, or soil improvement, would be more feasible if bioelectrodes could be fabricated with simpler materials. Biochar with potentially improved electroactive properties (e-biochar) can be an ideal candidate for this scope, being at the same time widely available, biocompatible, and fully recyclable at its end-of-life as a soil amendment. Here we review the application of biochar to MET, to set benchmarks aimed at tuning the electroactive properties of such materials from the point of view of MET. The precursor biomass, thermochemical process conditions, and pre-, in situ-, and/or post-treatments should tailor optimized combinations of electrical conductivity, capacitance, superficial redox-active and electroactive functional groups, porosity distribution, and capacity to host electroactive microbial communities. We also discuss methods to rigorously characterize e-biochar properties and the most relevant multidisciplinary research challenges toward its application in large-scale MET. This work has been financed by the Italian Ministry of University and Research (MIUR), within the SIR2014 Grant, project RBSI14JKU3. Dr. R. Berenguer also thanks the Spanish Ministerio de Economía y Competitividad and FEDER funds (RYC-2017-23618 and CTM2015-71520-C2-1-R) for financial support. Ricardo Louro and Catarina Paquete thank Fundação para a Ciência e a Tecnologia (FCT) Portugal [PTDC/BBBBQB/4178/2014 and PTDC/BIA-BQM/30176/2017], by Project LISBOA-01-0145-FEDER-007660 (Microbiologia Molecular, Estrutural e Celular) funded by FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI), and by ITQB research unit GREEN-it “Bioresources for sustainability” (UID/Multi/04551/2013). This work has also received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 810856. This investigation has also received funding from the European Union’s Horizon 2020 research and innovation programme under the grant agreement No. 642190 (Project “iMETLAND”; http://www.imetland.eu).

P-postmodified polyaniline was obtained by reacting phosphorus trichloride (PCl3) and chlorodiphenylphosphine (PPh2Cl) and polyaniline (PANI), under mild conditions. The reaction was found to be very selective, as only the imine groups were involved in the P-functionalization, and efficient as well, affording a P-loading of 3 at.% and 5 at.% for PPh2Cl and PCl3, respectively. All the polymers were characterized by different techniques and the results were endorsed by theoretical calculations. Experimental and Density Functional Theory results proved that the reaction occurs through the imine groups and the phosphorus atoms, generating NP bonds. The electrochemical properties of the NP modified materials were evaluated and the catalytic activity towards oxygen reduction reaction was measured. It was found that a high concentration of phenyl groups from PPh2Cl (about 3 at.%) affected negatively the activity of the catalyst since they prevented the access of the oxygen molecules to the catalytic active sites. However, a lower amount of PPh2 groups (1 at.%) or the use of PCl3 avoided this hindrance and resulted in an improved catalytic activity with respect to pristine PANI. The authors thank MINECO, MICIUNIN, FIS2015-64222-C2-2-P and FEDER (RTI2018-095291-B-I00 and MAT2016-76595-R) for the financial support.

Knowledge of the carbon active sites for Oxygen Reduction Reaction (ORR) remains confusing and controversial and thus the detailed mechanism is still not clarified. Considering the nature of the carbon-oxygen interaction in active sites during the gasification reaction, it could be inferred that the sites for this reaction are the same as those participating in the ORR. Herein, the relationship between carbon-oxygen gasification properties and ORR activities was elucidated. Carbon materials including different structures and porosities were selected and extensively characterized in terms of structural and electrochemical properties. Regarding gasification properties, active surface area (ASA) and reactivity for carbon-oxygen reaction were determined. A good linear correlation is found between ORR activity and carbon-oxygen gasification reactivity. Interestingly, similar correlation is found between ORR activity or gasification reactivity and ASA, although two different slopes are observed for the analyzed samples, being higher for the carbon nanotubes (CNT) based samples. The results suggest that the active sites participating in the gasification reaction can be catalytic sites for ORR although the specific catalytic activity is determined by the carbon structure. Thus, active sites in CNT show higher activities toward ORR and carbon gasification reactivities than others. The authors gratefully acknowledge the financial support by MINECO (CTQ2015-66080-R MINECO/FEDER) and HEIWA NAKAJIMA FOUNDATION.

Synthesizing high-activity metal/heteroatom-co-doped carbon (M/H–C) electrocatalysts for the oxygen reduction reaction (ORR) is critical for the commercialization of fuel cells, but remains challenging because of the difficulty in making highly dispersed (M/H–C) electrocatalysts. Herein, a commercial ion-exchange resin, Amberlyst 15, is used as a support, and Co/2-methylimidazole is anchored on the ion-exchange site of the support to obtain Co/N/Amb as the precursor of the M/H–C electrocatalyst. After the precursor is pyrolyzed and converted into Co/N/C materials, it is activated with CO2, and the obtained material (act-Co/N/C) exhibits remarkable ORR activity with a high onset potential of 0.943 V (vs. the reversible hydrogen electrode) and an excellent kinetic current density comparable to commercial 5 wt% Pt/C in an alkaline medium. The favorable activity is mainly attributed to the ultra-dispersed CoNx and high porosity of act-Co/N/C. Our synthetic strategy could be applied to the preparation of other well-dispersed M/H–C materials. This work opens a new direction in the synthetic strategy of carbon materials. Financial support from MINECO (CTQ2015-66080-R) and HEIWA NAKAJIMA FOUNDATION is acknowledged.

The occurrence of hypoxic muddy sediments on shallow beaches and other sheltered areas is a well-known environmental problem, which negatively affects coastal areas, tourism potential, the public use of beaches and sediment biodiversity. The usual solution is limited to dredging and removal of sludge to a landfill site. In this study, a laboratory-scale experiment was performed to determine the effectiveness of two technologies: a modification of air sparging and a new approach based on injecting oxygen-saturated seawater in hypoxic muddy sediments (oxygen-saturated seawater injections method), for remediating sludge in coastal sediments, minimizing environmental impact respect to dredging. Our results showed that both technologies significantly increased dissolved oxygen content in pore water, facilitating the oxidation of more than 90% of the organic matter, and other reduced inorganic compounds such as sulphide, with the consequent increase in sulphate concentration from 0.3 to 3.0 g·L−1. Moreover, a rise of redox potential from − 258 mV to above 200 mV, and a dramatic drop in chemical oxygen demand were also indicators that oxic conditions had been restored. After 65 days, soft, black, muddy and hypoxic sediment with high organic matter content and a characteristic foul odour was transformed into well-oxygenated sediment, which had a low organic matter content and had lost its initial shiny black colour and odour. The main difference between both technologies was the depth influenced by sediment remediation; oxygen-saturated seawater injections affected deeper areas than clean pressurized air injections. This work was supported by Own Research Program to MC and CB of the University of Alicante (Grant Number [PC15-05]) and Route Pont SL.

Chemical hydrogen storage stands as a promising option to conventional storage methods. There are numerous hydrogen carrier molecules that afford satisfactory hydrogen capacity. Among them, ammonia borane has attracted great interest due to its high hydrogen capacity. Great efforts have been devoted to design and develop suitable catalysts to boost the production of hydrogen from ammonia borane, which is preferably attained by Ru catalysts. The present review summarizes some of the recent Ru-based heterogeneous catalysts applied in the hydrolytic dehydrogenation of ammonia borane, paying particular attention to those supported on carbon materials and oxides. This work was financed by the MICINN, FEDER (RTI2018-095291-B-I00). MNG thanks the Plan GenT project (CDEIGENT/2018/027) for their financial support. DST thanks MICINN for the “Juan de la Cierva” contract (IJCI-2016-27636) and the Vicerrectorado de Investigación y Transferencia de Conocimiento de la Universidad de Alicante (GRE19-16).

This work evaluates the feasibility of electrochemical regeneration of granular activated carbon used in drinking water treatment plants as a real alternative to thermal regeneration. Two pilot-plant-scale reactors, with a capacity of 10−15 kg, have been designed using two different configurations, parallel plate electrodes and concentric cylindrical electrodes. The optimization of the anode material has also been studied and Pt/Ti, RuO2/Ti and IrO2/Ti have been used. After the regeneration and, thus, recovery of the porosity the samples were tested in the adsorption of bisphenol A. In the electrochemical regeneration, recovery of the porosity of spent activated carbon until 100 % and 96 % with respect to the pristine activated carbon using Pt/Ti anode after 3 h of treatment, has been achieved. The regeneration process produces a small increase in the number of surface oxygen groups. No important differences have been observed among the tested anodes and RuO2/Ti and IrO2/Ti can be an economic alternative to Pt/Ti. Bisphenol A adsorption kinetics was slower in regenerated activated carbons probably due to the formation of surface oxygen groups. However, the adsorption capacity was similar in the regenerated samples and the pristine one. This work was supported by the European Union-Horizon 2020 (PORTABLECRAC - SPIRE09 - 2017 Nº 768905).

The adsorption and electroadsorption of bromide from natural water has been studied in a filter-press electrochemical cell using a commercial granular activated carbon as the adsorbent. During electroadsorption experiments, different voltages were applied (2 V, 3 V and 4 V) under anodic conditions. The presence of the electric field improves the adsorption capacity of the activated carbon. The decrease in bromide concentration observed at high potentials (3 V or 4 V) may be due to the electrochemical transformation of bromide to Br2 . The anodic treatment produces a higher decrease in the concentration of bromide in the case of cathodic electroadsorption. Moreover, in this anodic electroadsorption, if the system is again put under open circuit conditions, no desorption of the bromide is produced. In the case of anodic treatment in the following adsorption process after 24 h of treatment at 3 V, a new decrease in the bromide concentration is observed as a consequence of the decrease in bromide concentration after the electrochemical stage. It can be concluded that the electroadsorption process is effective against the elimination of bromide and total bromine in water, with a content of 345 and 470 µg L−1 , respectively, reaching elimination values of 46% in a single-stage electroadsorption process in bromide and total bromine. The application of the electric field to the activated carbon with a positive polarization (anodic electroadsorption) increases the adsorption capacity of the activated carbon significantly, achieving a reduction of up to 220 µg L−1 after 1 h of contact with water. The two stage process in which a previous electrochemical oxidation is incorporated before the electroadsorption stage significantly increased the efficiency from 46% in a single electroadsorption step at 3 V, to 59% in two stages.

The electrochemical performance of nitrogen-doped and non-doped superporous activated carbons as electrodes for supercapacitors was assessed in organic and ionic liquid-based electrolytes. The nitrogen functionalization was carried out through post-modification treatments at mild conditions to produce N-doped activated carbons that preserve the microporosity of the pristine carbon material. The electrodes based on these materials provide large capacitance values (up to 150–180 F/g) in both 1 M Pyr14TFSI/PC and 1 M Pyr14BF4/PC due to their tailored porous texture, given by their well-developed microporosity and low mesopore volume. The electrochemical double layer capacitors based on these materials displayed outstanding capacitance (37–40 F/g and 14 F/cm3) and energy values (44–48 Wh/kg and 16–17 Wh/L). The nitrogen-doped activated carbons evidence high stability at positive and negative polarization potentials due the presence of specific N functionalities. The results prove that surface chemistry of carbon materials plays a key role on their degradation under high operation voltage conditions. The durability of the devices can be improved by doping carbon electrodes with selected nitrogen groups, such as nitrogen heterocycles and amine-like surface functionalities. The authors thank MICINN, FEDER (RTI2018-095291-B-I00 and ENE2017-90932-REDT). MJML acknowledges financial support through VALi+d grant (ACIF/2015/374) and mobility grant (BEFPI/2017/036).

An enzymatic metal-free electrochemical biosensor based on immobilized glucose oxidase on a N-doped porous carbon material has been studied for the detection of glucose in different real samples. The N-doped carbon material, which contains quaternary nitrogen groups, has been obtained by heat treatment of polyaniline. These functionalities promote the electrocatalytic activity to oxygen reduction reaction. The electrochemical biosensor presents a remarkable electrochemical activity towards oxygen reduction reaction, being able to detect changes in oxygen concentration generated by the enzymatic oxidation of glucose, allowing the indirect detection of this compound in phosphate buffered solution (0.1 M PB solution, pH=7.2). The metal-free electrochemical biosensor shows an outstanding performance, with a linear detection range between 5 µM and 5 mM and a high sensitivity of 23.57±1.77 µA mM−1 cm−2 at -0.4 V vs. Ag/AgCl. At these conditions, the addition of ascorbic acid, dopamine, uric acid and l-gluconic acid does not interfere with glucose determination. The method has been successfully applied to human urine and commercial sugary drink samples, without significant matrix effects, providing an alternative for glucose detection. The authors would like to thank MINECO and FEDER (RTI2018–095291-B-I0 0 and PID2019–105923RB-I0 0) for the financial sup- port. A.F.Q.J. gratefully acknowledges Generalitat Valenciana for the financial support through Santiago Grisolia grant (GRISO- LIA/2016/084).

This work studies the removal of o-cresol from wastewater by using ozonation followed by adsorption onto sodium natural bentonite (Na-Bent). The degradation of o-cresol was followed by UV-Vis. During ozonation, 2-methylbenzoquinone (2-mBQ) and 2-methylhydroquinone (2-mHQ) were identified as two of the main by-products, while the pH decrease suggested the breakage of aromatic compounds into smaller organic acids. After 30 min treatment, the o-cresol degradation for 250–62.5 mg/L solutions was found between 64–85%, respectively. Next, the wastewater containing persistent o-cresol and by-products was contacted with Na-Bent adsorbent. The solutions and physicochemical properties of Na-Bent were analysed, before and after adsorption, by UV-Vis, FTIR, XRD and N2 adsorption-desorption. Moreover, equilibrium and kinetic experiments were carried out to study the adsorptive properties of the Na-Bent. While sole ozonation or adsorption failed on the remediation of o-cresol solutions, the obtained results show that the contact of ozonated solutions with Na-Bent led to almost total removal of the o-cresol initial concentrations (between 96% and 99%). This excellent performance is assigned to the high volume of interlayer micropores and the suitable surface chemistry of this natural adsorbent. The authors would like to thank the Algerian Directorate General of Scientific Research and Technological Development (DGRSDT) and the Ministry for Higher Education and Scientific Research for the financial support for this work. In addition, the Spanish Ministerio de Economía y Competitividad and FEDER funds (RYC-2017-23618) are gratefully appreciated.

In this work, a bidentate Schiff base ligand (HL) containing N and O as donor heteroatoms has been used to synthesize series of new stable metal complexes of general composition of M(L)2 with M = Mn, Ni and VO. This ligand was obtained from condensation of 2-methoxybenzylamine on 2,3-dihydroxybenzaldehyde in methanolic solutions in which its complexes were obtained by mixing the corresponding metal acetate salt and the ligand in 1:2 molar ratio. The resulting three complexes have been characterized by different analytical techniques like FT-IR, UV-Vis, mass spectroscopy, thermogravimetry and cyclic voltammetry, to identify their molecular structures and redox/electrochemical properties. Moreover, the effect of the metal on the complexes electronic properties with their reactivity has also been studied by Density Functional Theory (DFT). The stable structures were optimized by using the hybrid B3LYP/6–31 G method. The spectroscopic data obtained suggest that the metal is bonded to the ligand through the phenolic-like oxygen and the imine-type nitrogen atoms. Electronic and vibrational absorption spectra of the nickel complex was found to be of square-planar geometry while square-pyramidal and octahedral geometries have been proposed for VO(IV) and Mn(II) complexes, respectively. The thermogravimetric analyses of these complexes confirmed the presence of water molecules in their structures and thermal decomposition led to the formation of metal oxides as the latest residues. The voltammogram of the Ni(II) complex suggests the existence of quasi-reversible redox system in DMSO solution. The authors would like to thank the MESRS and DG-RSDT (Ministère de l’Enseignement Supérieur et de la Recherche Scientifique et la Direction Générale de la Recherche et du Développement Technologique-Algérie) for their financial support. Financial support from the Ministerio de Economía y Competitividad (Spain) and FEDER (MAT2016-76595-R and RYC-2017-23618) is also gratefully acknowledged.

Biomass upgrading is a promising approach to face the current energy consumption and chemicals production. Lignocellulosic biomass residues have taken the lead in this field. In this study, hemp residue-based activated carbons (ACs) were prepared by H3PO4-assisted hydrothermal carbonization (HTC) using a low concentration of H3PO4 (25 wt%). ACs with a high porosity development were obtained (SBET > 1200 m2 g−1), and they were subsequently functionalized with nitrogen groups using mild conditions. As-synthesized ACs were also heat-treated to enhance the electrical conductivity, improving the electrochemical performance. As a proof of concept, electrochemical capacitors (ECs) based on as-prepared ACs in aqueous and organic electrolytes, showing energy densities comparable to those of a capacitor based on an AC used in commercial capacitors. The most attractive outcome of this study is the straightforward, cost-effective, and sustainable methodology to prepare high added-value functional ACs with great potential for energy and environmental applications. This research was partially supported by the MICINN, FEDER (RTI2018-095291-B-I00). JCG thanks for her predoctoral scholarship (GRISOLIA/2018/105) funded by the Generalitat Valenciana and DST thanks MICINN for the “Juan de la Cierva” contract (IJCI-2016-27636).

Development of effective direct electron transfer is considered an interesting platform to obtain high performance bioelectrodes. Therefore, designing of scalable and cost-effective immobilization routes that promotes correct direct electrical contacting between the electrode material and the redox enzyme is still required. As we present here, electrochemical entrapment of pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) on single-wall carbon nanotube (SWCNT)-modified electrodes was carried out in a single step during electrooxidation of para-aminophenyl phosphonic acid (4-APPA) to obtain active bioelectrodes. The adequate interaction between SWCNTs and the enzyme can be achieved by making use of phosphorus groups introduced during the electrochemical co-deposition of films, improving the electrocatalytic activity towards glucose oxidation. Two different procedures were investigated for electrode fabrication, namely the entrapment of reconstituted holoenzyme (PQQ-GDH) and the entrapment of apoenzyme (apo-GDH) followed by subsequent in situ reconstitution with the redox cofactor PQQ. In both cases, PQQ-GDH preserves its electrocatalytic activity towards glucose oxidation. Moreover, in comparison with a conventional drop-casting method, an important enhancement in sensitivity was obtained for glucose oxidation (981.7 ± 3.5 nA mM-1) using substantially lower amounts of enzyme and cofactor (PQQ). The single step electrochemical entrapment in presence of 4-APPA provides a simple method for the fabrication of enzymatic bioelectrodes. The authors would like to thank MICINN (PID2019-105923RB-I00) for the financial support. A.F.Q.J. gratefully acknowledges Generalitat Valenciana for the financial support through Santiago Grisolia grant (GRISOLIA/2016/084), to the University of Alicante for the support in the mobility program through the Escuela de Doctorado (EDUA).

High-quality performance of catalysts is increasingly required to meet industry exigencies. However, chemical synthesis is often insufficient to maximize the potential properties of the catalysts. On the other hand, electrochemical synthesis has arisen as a promising alternative to overcome these limitations and provide precise control in the preparation of catalysts. In this sense, this work involved the well-controlled electrochemical synthesis of a catalyst based on platinum nanoparticle deposition on carbon nanotubes using only electrochemical treatments. Thin films of functionalized carbon nanotubes were cast onto the surface of a glassy carbon electrode using potential pulsed electrodeposition, resulting in a better distribution of the carbon nanotubes on the electrode when comparing with traditional methods. Then, platinum nanoparticles were electrodeposited on the carbon nanotube-modified electrode. To check the performance of the catalyst and the relevance of the electrochemical synthesis treatments, the samples were analyzed as electrocatalysts towards methanol electrooxidation, showing an important improvement in the catalytic activity in comparison with electrodes that were prepared by traditional methodologies. This research was funded by MICINN and FEDER (RTI2018-095291-B-I00 and PID2019-105923RB-I00), “Juan de la Cierva” contract (IJCI-2016-27636), and the Vicerrectorado de Investigación y Transferencia de Conocimiento de la Universidad de Alicante (GRE19-16).

One of the most challenging targets in oxygen reduction reaction (ORR) electrocatalysts based on N-doped carbon materials is the control of the pore structure and obtaining nanostructured thin films that can easily be incorporated on the current collector. The carbonization of nitrogen-containing polymers and the heat treatment of a mixture of carbon materials and nitrogen precursor are the most common methods for obtaining N-doped carbon materials. However, in this synthetic protocols, the surface area and pore distribution are not controlled. This work enables the preparation of 2D-ordered N-doped carbon materials through the carbonization of 2D polyaniline. For that purpose, aniline has been electropolymerized within the porous structure of two different templates (ordered mesoporous Silica and ordered mesoporous Titania thin films). Thus, aniline has been impregnated into the porous structure and subsequently electropolymerized by means of chronoamperometry at constant potential. The resultant samples were heat-treated at 900 &deg, C with the aim of obtaining 2D N-doped carbon materials within the template structures. Polyaniline and polyaniline-derived carbon materials have been analyzed via XPS and TEM and characterized by electrochemical measurements. It is worth noting that the obtained 2D-ordered mesoporous N-doped carbon materials have proved to be highly active electrocatalysts for the ORR because of the formation of quaternary nitrogen species during the heat treatment.

Nitrogen functionalization of a highly microporous activated carbon (SBET &gt, 3000 m2/g), to be used as electrode of electric double layer capacitor (EDLC), was carried out by different methods based on organic chemistry protocols at low temperature and selective thermal post-treatments under inert atmosphere. The combination of both methods allowed the production of carbon materials with very similar surface area (2400&ndash, 3000 m2/g) and different surface chemistry. The nitrogen functionalization by chemical methods produce the attachment of 4 at. % N (XPS) by consumption of oxygen functional groups. The thermal treatments rearrange the surface chemistry by decreasing and converting both nitrogen and oxygen moieties. The effect of surface chemistry on the performance of these materials as electrodes for symmetric supercapacitors was analyzed in organic electrolyte (1M TEMABF4/propylene carbonate). The devices showed high gravimetric capacitance (37&ndash, 40 F/g) and gravimetric energy density (31&ndash, 37 Wh/kg). The electrochemical stability of the EDLC was evaluated by a floating test under severe conditions of voltage and temperature. The results evidence an improvement of the durability of nitrogen-doped activated carbons modified by chemical treatments due to the decrease of detrimental oxygen functionalities and the generation of nitrogen groups with higher electrochemical stability.

Excellent Pd supported on carbon catalysts for the dehydrogenation of formic acid were synthesized from a lignocellulosic biomass residue. The preparation of the carbon support consisted of a H3PO4-assisted hydrothermal carbonization (HTC) and activation of a hemp residue and subsequent nitrogen functionalization. It was observed that the presence of nitrogen groups influenced both the size and the electronic properties of the Pd nanoparticles, which ultimately affected their catalytic properties. Furthermore, the catalytic performance also depended on the synthesis conditions used in the preparation of the catalysts (i.e., reduction of the Pd nanoparticles with NaBH4 prior to the catalytic test or in situ reduction). The best-performance catalysts (Pd/N-HTC (n.r.)), which were prepared by in situ reduction of the nanoparticles, displayed a remarkable catalytic activity with a very high TOF number of 8365 h–1 (TOF value calculated for the 2nd catalytic run and expressed per surface Pd atom) and outstanding stability during 6 consecutive reaction cycles, although the initial activity is maintained for 12 cycles. The catalytic system studied is among the most stable ever reported Pd-based heterogeneous catalysts for the dehydrogenation of formic acid. This work was financed by the MICINN, FEDER (RTI2018-095291-B-I00). J.C.-G. acknowledges her predoctoral scholarship (GRISOLIA/2018/105) funded by the Generalitat Valenciana. M.N.-G. thanks the Plan GenT project (CDEIGENT/2018/027) for the financial support. D.S.-T. thanks the MICINN for the “Juan de la Cierva” contract (IJCI-2016-27636).

Pt-doped SnO2–Sb electrodes constitute promising candidates for the electrochemical abatement of refractory pollutants, but their efficacy to oxidize emerging pollutants remains uncertain. In this work, the electrochemical oxidation of diclofenac, pharmaceutical pollutant, on Pt-doped Ti/SnO2–Sb electrodes has been studied by cyclic voltammetry and galvanostatic treatment in neutral medium. In parallel, the capability of these anodes to generate hydroxyl radicals (OHs) has been analyzed by in-situ UV spectroelectrochemical measurements. For comparison purposes, the responses of Ti/SnO2–Sb and commercial Ti/Pt and BDD anodes were also evaluated. The voltammetric and electrolysis results show that the different Ti/SnO2–Sb anodes can effectively oxidize and mineralize diclofenac, so their electrochemical activity lies in between that of Ti/Pt and BDD. The incorporation of small amounts of Pt (3–13 at.%) into the SnO2–Sb coatings, despite hindering the OHs generation, enhances the kinetics and efficiency for diclofenac oxidation and mineralization. This better overall response is attributed to a synergy between diclofenac-Pt interaction and efficient OHs generation. Pt-doped Ti/SnO2–Sb electrodes are then presented as a cheaper potential alternative to BDD for treating pharmaceutics pollutants in waters. The authors thank the Spanish Ministerio de Economía y Competitividad (MINECO) and FEDER funds (grants MAT2016-76595-R and RYC-2017-23618) and Generalitat Valenciana (grant PROMETEO/2018/087) for financial support.

Metal-free carbon-based catalysts have gained much attention during last years because of their interesting properties towards oxygen reduction reaction. Intrinsic parameters of carbon materials such as porosity, structural order, conductivity and defects have proved to have a strong influence in the catalytic activity of these materials. However, the highest differences in catalytic activity are obtained via doping with heteroatoms, being nitrogen the most remarkable in terms of activity and selectivity. One of the most challenging goals of the scientific community is to unravel the role of the functional groups in order to design an optimized material. However, the complexity of isolating one specific functionality, the difficult unambiguous characterization of the species and the influence of the intrinsic properties of the carbon materials, make the identification of the active sites a complex and controversial issue. This review presents a critical assessment about the role of heteroatoms on ORR from the analysis of the literature that combine both experimental work and computational modelling. The authors thank Ministerio de Ciencia, Innovación y Universidades and FEDER for financial support (Project RTI2018-095291-B-I00, ENE2017-90932-REDT and MAT2016-76595-R).

Various carbon materials were used as support of polyvinylpyrrolidone (PVP)-capped Pd nanoparticles for the synthesis of catalysts for the production of hydrogen from formic acid dehydrogenation reaction. Among investigated, MWCNT-supported catalysts were the most promising, with a TOF of 1430 h−1 at 80°C. The presence of PVP was shown to play a positive role by increasing the hydrophilicity of the materials and enhancing the interface contact between the reactant molecules and the catalytic active sites. The authors would like to acknowledge Generalitat Valenciana (PROMETEO/2018/076 project) for the financial support. Furthermore, MN-G would like to thank Generalitat Valenciana and Plan GenT (CDEIGENT/2018/027) for the postdoctoral grant.

Hybrid silica-modified materials were synthesized on glassy carbon (GC) electrodes by electroassisted deposition of sol-gel precursors. Single-wall carbon nanotubes (SWCNTs) were dispersed in a silica matrix (SWCNT@SiO2) to enhance the electrochemical performance of an inorganic matrix. The electrochemical behavior of the composite electrodes was tested against the ferrocene redox probe. The SWCNT@SiO2 presents an improvement in the electrochemical performance towards ferrocene. The heterogeneous rate constant of the SWCNT@SiO2 can be enhanced by the insertion of poly(3,4-Ethylendioxythiophene)-poly(sodium 4-styrenesulfonate) PEDOT-PSS within the silica matrix, and this composite was synthesized successfully by reactive electrochemical polymerization of the precursor EDOT in aqueous solution. The SWCNT@SiO2-PEDOT-PSS composite electrodes showed a heterogeneous rate constant more than three times higher than the electrode without conducting polymer. Similarly, the electroactive area was also enhanced to more than twice the area of SWCNT@SiO2-modified electrodes. The morphology of the sample films was analyzed by scanning electron microscopy (SEM). This research was funded by the Directorate General of Scientific Research and Technological Development (DGRSDT) (Algeria) and by the Ministerio de Ciencia, Innovación y Universidades (MAT2016-76595-R) and by the Conselleria de Educación, Investigación, Cultura y Deporte, Generalitat Valenciana (PROMETEO/2018/087).

[EN] A set of fluoro-functionalized polyaniline conducting polymers was synthesized by cyclic scanning of the potential from acidic solutions containing aniline and 2-fluoroaniline monomers. The monomer feed ratio was varied to modulate the composition of the synthesized materials. The fluorination level of the copolymers was quantified from X-ray photoelectron spectroscopy. The upper inversion potential of the cyclic scans was proved as a suitable tool to tune the fluorination level, as the reactivity of the growing chains depends strongly on that experimental parameter. We found that terminal fluorinated anilines present a reactivity for homocoupling 5 times lower than for heterocoupling, independently of the limiting potential. Conversely, aniline terminal groups present a reactivity strongly dependent on the limiting potential, favoring the heterocoupling reactions at high inversion potentials. The maximum fluorination level of polyaniline rings achieved is about 75%. (C) 2020 Elsevier Ltd. All rights reserved., The authors wish to thank Generalitat Valenciana (PROMETEO/2018/087) for financial support. Nesrine Saidani would like to thank the Tunisian Ministry of Higher Education and Research for funding her stay at the University of Alicante.

The stability of supercapacitors is the key factor for their use under high temperature, high voltage and long-term durability. To improve the supercapacitor stability, there is a need to understand the degradation mechanism. In this work, the degradation sites in a carbon electrode at negative potential range are investigated in two common organic electrolytes: 1 M Et4NBF4 dissolved in propylene carbonate and in acetonitrile. To elucidate the common factor over a wide range of carbon materials, we examined eight kinds of carbon materials including activated carbons, carbon blacks, zeolite-template carbon (high surface area and a large amount of carbon edge sites) and graphene mesosponge (high surface area and a little amount of carbon edge sites). Their surface structures are distinguished into two regions: carbon basal planes and edge sites by nitrogen physisorption and high-sensitivity temperature-programmed desorption up to 1800 °C. Unlike the degradation at positive potential range, initial degradation reactions at negative potential range occur mainly on the carbon basal planes rather than the edge sites. This finding is corroborated by the theoretical calculation. This work was supported by JSPS KAKENHI (grant Nos. 17H01042 and 19H00913); the Dynamic Alliance for Open Innovation Bridging Human, Environment, and Materials program; and the Network Joint Research Centre for Materials and Devices. R. T. acknowledges the China Scholarship Council for the financial support. MINECO and FEDER (CTQ2015-66080-R MINECO/FEDER) are acknowledged for financial support.

Electrochemical functionalization of pristine Multi-walled Carbon Nanotubes (MWCNTs) and oxidized MWCNTs by nitric acid with 4-aminophenyl phosphonic acid (4-APPA) has been studied. Electrochemical modification has been carried out by cyclic voltammetry using different upper potential limits, what results in the incorporation of N and P functionalities through oligomerization and covalent attachment. The electrochemical characterization shows that there are important differences among the functionalized materials derived from the pristine MWCNTs or the oxidized materials. For the pristine MWCNTs, well-defined redox processes are observed. Characterization by X-Ray photoelectron spectroscopy, Raman spectroscopy and electron microscopy, show that oligomerization is easier for the pristine MWCNTs and the presence of oligomer chains are clearly distinguished for the lowest oxidation potentials. However, the presence of surface oxygen groups in the oxidized MWCNTs modify the interaction of the 4-APPA with the surface promoting mainly covalent attachment. The authors would like to thank MINECO and FEDER (MAT2016-76595-R) for the financial support. A.F.Q.J. gratefully acknowledges Generalitat Valenciana for the financial support through Santiago Grisolia grant (GRISOLIA/2016/084).

Adequate electrochemical characterization of electrode material/biofilms is crucial for a comprehensive understanding and comparative performance of bioelectrochemical systems (BES). However, their responses are greatly affected by the metabolic activity and growth of these living entities and/or the interference of electrode wiring that can act as an electroactive surface for growth or constitute a source of contamination by corrosion. This restricts the meaningful comparison of the performance of distinct electrode materials in BES. This work describes a methodology for simultaneous electrochemical control and measurement of the microbial response on different electrode materials under the same physicochemical and biological conditions. The method is based on the use of a single channel potentiostat and one counter and reference electrodes to simultaneously polarize several electrode materials in a sole bioelectrochemical cell. Furthermore, various strategies to minimize wiring corrosion are proposed. The proposed methodology, then, will enable a more rigorous characterization of microbial electrochemical responses for comparisons purposes. • Experimental Set-up allows to polarize several working electrodes at the same time. • Chronoamperometry can be performed simultaneously with a potentiostat. • The physicochemical and biological conditions in each working electrode will be exactly the same, Graphical Abstract Image, graphical abstract

The hybridization of clay minerals with conducting polymers receives great interest for different potential applications, including environmental remediation. This work studies and compares the electrochemical properties of two different clays, montmorillonite (Mont) and diatomite (Diat), and their respective clay/PEDOT-PSS hybrid materials in H2SO4 medium. The hybrid materials were prepared by electropolymerization of EDOT in the presence of PSS. The physico-chemical and electrochemical properties of both clays were analyzed by different techniques, and the influence of the clay properties on electropolymerization and the electroactivity of the resulting clay/PEDOT-PSS hybrids was investigated. Specifically, the Fe2+/Fe3+ redox probe and the oxidation of diclofenac, as a model pharmaceutical emerging pollutant, were used to test the electron transfer capability and oxidative response, respectively, of the clay/PEDOT-PSS hybrids. The results demonstrate that, despite its low electrical conductivity, the Mont is an electroactive material itself with good electron-transfer capability. Conversely, the Diat shows no electroactivity. The hybridization with PEDOT generally enhances the electroactivity of the clays, but the clay properties affect the electropolymerization efficiency and hybrids electroactivity, so the Mont/PEDOT displays improved electrochemical properties. It is demonstrated that clay/PEDOT-PSS hybrids exhibit diclofenac oxidation capability and diclofenac concentration sensitivity. This research was funded by Spanish Ministry of Science, Innovation and Universities (grant number RYC-2017-23618) and Generalitat Valenciana (Prometeo2018/087 project).

A new portable electrochemical sensor based on 4-aminobenzoic acid-modified herringbone carbon nanotubes (hCNTs-4ABA/Au-IDA) has been developed for the simultaneous determination of ascorbic acid (AA) and uric acid (UA) in physiological fluids. AA and UA were quantified by chronoamperometry at 0.1 and 0.32 V, respectively, in phosphate buffer solution (PBS 0.25 M, pH 7.0). Significant results were obtained for the separate quantification of AA and UA, with a limit of detection (LOD) of 0.65 μM for both analytes, and sensitivities of (9.0 ± 0.4) A g−1 mM−1 and (8.8 ± 0.3) A g−1 mM−1 for AA and UA, respectively. Repeatability was studied at 50 μM for AA and UA, providing relative standard deviations (RSD) lower than 9%. Additions of glucose, dopamine and epinephrine did not interfere with the AA and UA determination. Furthermore, UA did not interfere with AA determination at 0.1 V, although AA additions increased the current recorded at 0.32 V. The method has been successfully applied to human urine, perspiration and serum samples, without significant matrix effects, which allows for the use of an external calibration and the analysis of all the matrices investigated. This work is supported by the Generalitat Valenciana (Prometeo2013/038) and by the Ministerio de Economia y Competitividad (MAT2016–76595-R). A. Abellán also thanks the Generalitat Valenciana for her fellowship.

Two zeolite templated carbons (ZTC) with comparable structure and different surface chemistry have been synthesized by chemical vapor deposition of different precursors, producing a non-doped and a N-doped carbon material (4 at. % XPS) in which most of the functionalities are quaternary N. A larger specific capacitance (farads per surface area) has been measured in acid electrolyte for the N-doped ZTC, that can be related to an improved wettability due to the presence of nitrogen and oxygen. The capacitance of N-doped ZTC is lower in alkaline electrolyte, probably due to the loss of electrochemical activity of certain oxygen functionalities. Interestingly, the electro-oxidation process of N-ZTC implies lower irreversible currents (providing higher electrochemical stability) than for ZTC. The presence of quaternary nitrogen greatly improves the electric conductivity of N-ZTC, which shows a superior rate performance. ZTC and N-ZTC capacitors were constructed using 1 M H2SO4. Under the same conditions, N-doped ZTC based capacitor has higher energy density, 6.7 vs 5.9 W h/kg. The power density of N-ZTC is four times higher, producing an outstanding maximum power of 98 kW/kg. These results provide clear evidences of the advantages of doping advanced porous carbon materials with nitrogen functionalities. The authors would like to thank GV and FEDER (PROMETEOII/2014/010), projects CTQ2015-66080-R (MINECO/FEDER) and MAT2016-76595-R (MINECO/FEDER) for financial support. MJML acknowledges Generalitat Valenciana for the financial support through a VALi+d contract (ACIF/2015/374).

Electrochemically generated chemiluminescence (ECL) from solid-state poly(9,9′-octylfluorene) films was obtained by the successive electrochemical injection of polarons with opposite sign (annihilation ECL) in double potential steps. The processes involved in the recombination of polarons, the quenching of the electrochemically generated excitons, and the emission stability have been also analyzed. A systematic study at various electrochemical potentials has been carried out to determine optimal conditions to obtain a maximum ECL intensity, particularly with potentials of 0.4 V beyond the doping onsets (for both p- and n-doping). Results show that while the ECL emission is slightly affected by the potential of the emission, it is strongly dependent on the charging potential. Under large charging potential, the electrochemically generated excitons formed in the emission step get quenched by an excess of polarons and bipolarons that are detrimental to ECL. The maximum emission is obtained when the applied potentials are 0.4 V over the doping onset of the polymer conjugated chain. After partial depletion of the excess of polarons, the emission coming from the recombination of balanced polarons of opposite sign is observed. The stability of ECL emission in the optimal range was determined in continuous cathodic–anodic pulses. A rapid loss of the intensity in the initial stages is observed due to the dissolution of low molecular weight polymer fragments that become soluble upon electrochemical doping. The emission spectrum remains stable during the complete lifetime of the polymer. The spectral shape of PFO films indicates that the emission occurs mainly from the β-phase domains in which the electrochemical charge is preferentially injected. Authors acknowledge financial support from the Spanish Ministry of Economy Explora Ciencia Project MAT2013-49534-EXP.

In this study, multi-wall carbon nanotubes (MWCNTs) were electrochemically modified with nitrogen and phosphorus species and employed as platform to immobilize pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) for the fabrication of bioelectrodes for glucose detection. Depending on the upper potential limit used during the electrochemical modification of MWCNTs, the nature and amount of the nitrogen and phosphorus species incorporated in the carbon material surface can be selectively controlled. These species act as anchoring groups for the immobilization of the PQQ-GDH. The value of the upper potential limit used in the electrochemical modification influences the electron-transfer rate between the electrode and the enzyme. The performance of the bioelectrodes for glucose oxidation and detection is improved by the electrochemical modification conditions, leading to an increased sensitivity towards glucose oxidation from 39.2 to 53.6 mA gMWCNT−1 mM−1 in a linear range between 0.1 to 1.2 mM. This electrochemical modification is considered as an alternative for the preparation of highly sensitive glucose bioelectrodes. The authors would like to thank Ministerio de Ciencia e Innovación (PID2019-105923RB-I00) for the financial support. A.F.Q.J. gratefully acknowledges Generalitat Valenciana for the financial support through Santiago Grisolia grant (GRISOLIA/2016/084), to the University of Alicante for the support in the mobility program through the Escuela de Doctorado (EDUA).

[EN] The understanding of exciton dynamics is a central issue in the operation of conjugated polymer-based optoelectronic devices, like solar cells, light-emitting diodes or electrochemiluminescent cells. In this work, we explore the applicability of combined in situ electrochemical fluorescence and UV-vis spectroscopies for the study of electrochemically induced quenching of photoluminescence as novel tools for the determination of exciton diffusion in a model conjugated polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylvynilene] (MEH-PPV). It is demonstrated that the quenching process observed upon electrochemical doping follows a linear Stern-Volmer mechanism at low doping levels, with a time-independent rate constant typical of diffusion-controlled annihilation processes. From the Stern-Volmer rate constant and the exciton-polaron critical distance, an exciton diffusion coefficient is derived whose value is in close agreement with those reported in the literature. These results support the suitability of these spectroelectrochemical techniques as fast and powerful alternative tools for the reliable determination of exciton diffusion coefficients in conjugated polymers., This work was supported by Generalitat Valenciana (Conselleria de Educacion, Investigacion, Cultura y Deporte) project PROMETEO/2018/087 and Spanish Ministerio de Ciencia e Innovacion (project PID2019105923RBI00)

Synthesis of electrode materials for accurate detection and quantification of uric acid without the interference effect of ascorbic acid is still considered an important field for health monitoring in human beings. As we present here, a methodology of composite materials synthesis have been developed to obtain electroactive materials, employing electrochemical methods in a single step based on titanium carbide and titanium dioxide entrapped into a polymer matrix of poly(N-phenyl-o-phenylenediamine). The presence of the TiC and TiO2 nanoparticles entrapped into the polymer matrix has provided enhancement in the conductivity, electron transfer kinetics and electrochemical activity towards uric acid oxidation. The electrochemical behavior of the composite materials towards ascorbic and uric acid oxidation demonstrated that electrochemical oxidation of uric acid has not been affected by the presence of ascorbic acid in solution, being a suitable platform for non-invasive detection and quantification of uric acid concentration in physiological samples without the interference of ascorbic acid. The authors wish to acknowledge the directorate General of Scientific Research and Technological Development (DGRSDT) (Algeria). Financial support from the Generalitat Valenciana (Prometeo2018/87) is gratefully acknowledged. D.S.T thanks MICINN for the “Juan de la Cierva” contract (IJCI-2016-27636).

Zeolite-templated carbons (ZTCs) composed of curved and single-layer graphene frameworks have uniform micropores (ca. 1.2 nm) and high surface areas (~4,000 m2/g). Owing to their outstanding properties originating from the porous structures, ZTCs have been used in many applications. In this work, we synthesized Co/N-doped ZTC (Co/N-ZTC) by complexing Co ion with 2-methylimidazole in Y zeolite to expand further utilization of ZTCs. The obtained Co/N-ZTC has a high surface area (ca. 2,000 m2/g) and single atomic Co species in CoNx moieties, which actually contributes to its excellent catalytic performance on oxygen reduction reaction. This synthetic concept is beneficial to fabricate single atomic transition metals coordinated with heteroatoms in ZTCs, which contributes to the progress of material design of single atomic catalyst–supported porous materials. A part of this work was supported by “Advanced Characterization Nanotechnology Platform, Nanotechnology Platform Program of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, Grant Number JPMXP09A20OS0024 at the Research Center for Ultra-High Voltage Electron Microscopy (Nanotechnology Open Facilities) in Osaka University. In particular, Scanning Transmission Electron Microscope measurement was supported by Dr. Kazuhisa Sato.

N-doped carbon materials were obtained using polyaniline (PANI) as precursor. Heat treatment of PANI and de-doped PANI (PANId) was performed using different temperatures −600 and 800 °C–. Two different atmospheres were used during the treatment: an inert atmosphere (N2) and another one consisting on a slightly oxidizing mixture of gases (3000 ppm O2 in N2). The prepared materials at 800 °C showed high values of capacitance, up to 170 and 255 F g−1 in basic and acid electrolytes, respectively, in spite of their low surface area. The electrocatalytic activity towards oxygen reduction reaction (ORR) of all materials was studied in basic and acid media. The heat treated materials at 600 °C did not show a good electrocatalytic activity due to their poor electrical conductivity. On the other hand, heat-treated materials at 800 °C showed an enhanced catalytic activity due to their higher conductivity and the presence of nitrogen and oxygen functionalities in the carbon surface. Interestingly, the heat treatment at 800 °C using a slightly oxidant atmosphere produces carbon materials with much higher ORR activity which seems to be related to the larger amount of N-edge and O-edge sites. Preliminary computational studies suggest that the presence of these nitrogen and oxygen functionalities in the vicinities of the carbon atom improves the catalytic performance of N-doped carbon materials in the ORR and that two adjacent active sites can produce the O2 reduction to H2O through a 4 electrons pathway. The authors thank MINECO of Spain and FEDER (CTQ2015-66080-R MINECO/FEDER and MAT2016-76595-R) and Generalitat Valenciana (PROMETEOII/2014/010) for the financial support. CGG gratefully acknowledges Generalitat Valenciana for the financial support through a Santiago Grisolía grant (GRISOLIA/2013/005).

Due to its large surface area, high electrical conductivity as well as mechanical and thermal stability, pristine graphene has the potential to be an excellent support for metal nanoparticles (NPs), but the scarce amount of intrinsic chemical groups/defects in its structure that could act as anchoring sites for the NPs hinders this type of use. Here, a simple strategy based on the stabilization of pristine graphene in aqueous dispersion with the assistance of a low amount of flavin mononucleotide (FMN) is shown to yield a material that combines high electrical conductivity and abundance of extrinsic anchoring sites, so that pristine graphene–metal (Pd and Pt) NP hybrids with good dispersion and metal loading can be obtained from FMN–stabilized graphene. The activity of these hybrids towards the methanol oxidation reaction (MOR) both in acidic and alkaline media is studied by cyclic voltammetry (CV) and their stability investigated by chronoamperometry. The pristine graphene–Pt NP hybrid prepared by this simple, eco–friendly protocol is demonstrated to outperform most previously reported pristine graphene– and reduced graphene oxide–metal NP hybrids as electrocatalyst for the MOR, both in terms of catalytic activity and stability, avoiding at the same time the use of harsh chemicals or complex synthetic routes., Financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) and the European Regional Development Fund (FEDER) through projects MAT2015-69844-R and MAT2016-76595-R is gratefully acknowledged. We also acknowledge partial funding by Plan de Ciencia, Tecnología e Innovación 2013-2017 del Principado de Asturias and FEDER through grant GRUPIN14-056. M.A-V. is thankful to MINECO and for his pre-doctoral contract. R.R.R acknowledges financial support from MINECO through “Juan de la Cierva” program (JCI-2012-12664).

The electrogeneration of pure 4,4′-di-tert-butylbiphenyl peroxide as an electrodeposit could be achieved on a platinum electrode through the anodic oxidation of p-tert butylphenol in the presence of Lutidine, in addition to several soluble oligomers. The electrochemical and theoretical studies have shown that the favored coupling reaction corresponds to the O–O bond, albeit it is generally being considered unstable. Without the strong base, a mixture of trimer, tetramer and pentamer was deposited. The peroxide product presents a different electroactivity to that of the phenolic compound, with the appearance of a redox process involving cathodic and anodic symmetrical peaks at −0.10/0.15 V versus SCE, which indicates the preference of the polymer to adhere onto the electrode surface. The thermal degradation has also been analyzed. Quantum-chemical calculations reveal the reason for the oxygen–oxygen coupling. The authors would like to thank the Tunisian Ministry of Higher Education and Research for its financial support as well as the King Saud University for its funding through the Research Group Project No RGP-VPP-243. They would also like to thank the Spanish Ministry of Economy and Competitiveness for its financial support and the STIs for the ERDF funds (MAT2013-42007-P) and the Generalitat Valenciana (PROMETEO2013/ 038).

Gold interdigitated microelectrodes (Au-IDA) modified with either graphene flakes exfoliated using flavin mononucleotide (FMN) (Gr-FMN) or graphene flakes and platinum nanoparticles (Pt-Gr-FMN) have been studied in the oxidation of uric acid (UA). An electrochemical method for the detection and quantification of UA in phosphate buffer solution at physiological pH (PBS, 0.25 M, pH 7) in the absence and presence of ascorbic acid (AA) has been studied by cyclic voltammetry. The quantification of UA was investigated by cyclic voltammetry, presenting an oxidation peak at 0.99 V with both modified electrodes. Linearity range of 60–578 μM and 60–345 μM has been found for Gr-FMN/Au-IDA and Pt-Gr-FMN/Au-IDA electrodes, respectively. Limits of detection of 18 μM were obtained for both electrodes, and the repeatability was studied at 177 μM providing 4% and 8% for Gr-FMN/Au-IDA and Pt-Gr-FMN/Au-IDA, respectively. AA interference has been studied by cyclic voltammetry, showing two clearly separated oxidation peaks, at 0.99 V for UA oxidation and at 0.74 V for Gr-FMN/Au-IDA and 0.70 V for Pt-Gr-FMN/Au-IDA for AA oxidation. Linearity range has been studied in presence of 250 μM AA obtaining a working range of 60–578 μM for Gr-FMN/Au-IDA electrode and of 60–288 μM with Pt-Gr-FMN/Au-IDA electrode. Limits of detection remain at 18 μM for both electrodes and the repeatability was studied at 177 μM providing 8% and 14% for Gr-FMN/Au-IDA and Pt-Gr-FMN/Au-IDA electrodes respectively. This work is supported by the Generalitat Valenciana (Prometeo2013/038) and by the Spanish Ministerio de Economía y Competitividad (MAT2013-42007-P). We also acknowledge partial funding of this work by Ministerio de Economía y Competitividad and the European Regional Development Fund (ERDF) through projectMAT2015-69844-R aswell as by Plan de Ciencia, Tecnología e Innovación 2013–2017 del Principado de Asturias and ERDF (project GRUPIN14-056). A. Abellán-Llobregat also thanks the Generalitat Valenciana for her fellowship and M. Ayán-Varela acknowledges his predoctoral contract (FPI) from Ministerio de Economía y Competitividad.

[EN] The chemical composition of a LaMnO3 perovskite was modified sequentially by an improved sol-gel method to include cobalt centers in some B sites formerly occupied by Mn. In this way, a representative set of materials of general formula LaMn1-xCoxO3 was obtained whose composition extends from LaMnO3 to LaCoO3. These perovskites, as promising materials for oxygen reduction or oxygen evolution reactions, were characterized by several imaging (SEM), spectroscopic (XPS, EDX) and diffraction (XRD) techniques to elucidate their structure and to demonstrate the existence of composition differences between the catalytic surface and the bulk material. Specifically, it was found that lanthanum ions prevail at the surface of the catalyst but high cobalt-substitution levels stimulate the surface enrichment in B cations in their respective higher oxidation states (Mn4+ and Co3+ against Mn3+ and Co2+). This phenomenon opens the possibility of tuning their electrocatalytic properties and to synthesize suitable materials for electrochemical reactions involving molecular oxygen. (C) 2019 Elsevier Inc. All rights reserved., The authors thank MINECO and FEDER (MAT2016-76595-R) for the financial support. J.X.F.-L. gratefully acknowledges MINECO for the financial support through FPI contract (BES-2017-081598).

The functionalization of high surface area microporous carbon materials by oxidative treatments receives great interest for multiple applications. The micropore structure of the material and the oxidation method could play an important role in the process. In this work, we analyze and compare the effects of liquid-phase chemical and alternative electrochemical oxidation treatments in the textural and chemical properties of four microporous carbon materials, namely a granular-, cloth-, and powder-like activated carbon (AC) and a powdery zeolite templated carbon (ZTC). Particularly, we provide new data on oxidation kinetics and changes on microporosity and surface chemistry of various microporous carbons. Characterization techniques reveal that the extent, textural changes, and selectivity of the oxidation greatly depend on the type of microporous material and the oxidation method. The incorporation of surface oxygen groups (SOGs) generally causes a more-or-less significant decrease in the measured micropore volume and the specific surface area. In the studied ACs, the extent of oxidation and BET surface area reduction augment with their micropore volume, and the textural changes seem to be governed by the micropore blockage by SOGs. The disordered microporous structure of these materials is then quite robust toward oxidation, but its heterogeneity may contribute to the lack of selectivity during this process. By contrast, the regular micropore framework of the ZTC is rapidly destroyed even under soft oxidizing conditions, but it is proposed to promote certain selectivity during oxidation. The high reactivity and structural fragility of ZTC are assigned to the weak interconnections and large number of exposed edge sites in its structure. Our results demonstrate the fast oxidation rate of chemical treatments under different conditions, especially in the case of ZTC, what is proposed to restrict the control and to limit the oxidizability and selectivity of these functionalization processes. Contrarily, the electrochemical treatments are proved to better control the kinetics of oxidative functionalization, what may explain the observed higher efficiency and selectivity for SOGs introduction and the minimization of degradation in fragile microporous structures. Financial support from the Spanish Ministerio de Economía y Competitividad and FEDER funds (RYC-2017-23618, MAT2016-76595-R) is gratefully acknowledged.

The increasing worldwide energy consumption has contributed to both the vast growth of greenhouse emissions from carbon-containing fuels-based sources (coal, petroleum, etc.) and the depletion of the aforementioned sources. Given this scenario, the development of inexpensive and high-performing energy storage devices, which have the least possible environmental impact, is needed. At this point, electrochemical capacitors (ECs) or supercapacitors are a particular alternative or complementary option to batteries and fuel cells (FCs). ECs present high power output and long cycle life, but little power density compared to conventional or Lithium-ion batteries. Therefore, ECs are going to play a pivotal role, not only in portable electronic devices, but also to provide power density in hybrid electric vehicles. Many efforts have been focused on improving the energy output of ECs, although its enhancement keeping the high power density is still the cornerstone of most investigations. Many studies have been conducted toward the development of electrode materials such as metal oxides, conducting polymers or novel carbons. Nevertheless, they have shown important shortcomings to be implemented (i.e., high cost, low electrical conductivity, poor stability, etc.). Recent studies put the spotlight on nitrogen-containing carbon materials as candidates to improve the ECs performance in terms of energy. Optimizing the ECs configuration (asymmetric and hybrid) is another approach reported to tackle the challenge. Additionally, it is important to mention that the design of carbon materials obtained from inexpensive precursors lately attracted the attention of the research community. This review compiles works performed in our research group over the last years. The effect of nitrogen groups present in the carbon network on the capacitance will be reported and the study of asymmetric configuration to enhance de energy density will be discussed, either opening the potential window or by increasing the capacitance. Moreover, a lignin-based ECs will be described as an environmentally friendly approach. Finally, perspective and conceivable research guidelines in order to hurdle the challenges proposed to implement the carbon materials in the field of ECs will be addressed. We want to acknowledge the financial support by the Ministry of Economy and Competitiveness of Spain (MINECO) and FEDER (CTQ2015-66080-R MINECO/FEDER and MAT2016-76595-R).

Hybridization of nanomaterials constitutes an interesting approach to boost and develop novel properties and applications. In this work, different polyaniline (PANI)-derived polymer-SiC nanocomposites have been successfully synthesized by facile surface-initiated polymerization of aniline (ANI) and/or 4-Anisidine (4ANS) on HCl-functionalized SiC. The obtained materials were characterized by different analytical techniques as well as solubility, conductivity and electrochemical tests. The effect of the nature and combination of the substituents in the polymer was analyzed. XRD; thermogravimetry; and vibrational FTIR spectroscopy revealed effective polymerization and interaction between the polymers and the SiC nanoparticles to form PANI-SiC, poly(ANI-co-4ANS)-SiC and P4ANS-SiC nanocomposites. The presence of electron-donating (para) -OCH3 substituents was found to hinder this interaction and/or to retard the polymerization, decreasing the content and crystallinity of the polymer in the nanocomposite. However, the dispersibility of the nanocomposites in different solvents greatly increased, and the electroactive and optical properties were affected. As a result, the poly(ANI-co-4ANS)-SiC nanocomposite exhibits higher dispersibility, lower band gap, similar conductivity and richer electroactivity than PANI-SiC, and an intermediate polymerization yield. Then, engineering the substituents of polymer chains is demonstrated to be an efficient approach to tailor the properties of (PANI)-derived polymer-SiC nanocomposites. The authors wish to acknowledge the directorate General of Scientific Research and Technological Development (DGRSDT) (Algeria).

Nitrogen-containing superporous activated carbons were prepared by chemical polymerization of aniline and nitrogen functionalization by organic routes. The resulting N-doped carbon materials were carbonized at high temperatures (600–800 °C) in inert atmosphere. X-ray Photoelectron Spectroscopy (XPS) revealed that nitrogen amount ranges from 1 to 4 at.% and the nature of the nitrogen groups depends on the treatment temperature. All samples were assessed as electrocatalysts for the oxygen reduction reaction (ORR) in alkaline solution (0.1 M KOH) in order to understand the role of well-developed microporosity as well as the different nitrogen functionalities on the electrocatalytic performance in ORR. It was observed that nitrogen groups generated at high temperatures were highly selective towards the water formation. Among the investigated samples, polyaniline-derived activated carbon carbonized at 800 °C displayed the best performance (onset potential of 0.88 V versus RHE and an electron transfer number of 3.4), which was attributed to the highest concentration of N–C–O sites. This research was funded byMINECO and European Regional Development Fund (RTI2018-095291-B-I00, MAT2016-76595-R and ENE2017-90932-REDT). MJML acknowledges financial support of Generalitat Valenciana through VALi+d grant (ACIF/2015/374). DST thanks MINECO for a ‘Juan de la Cierva’ contract (IJCI-2016-27636).

Different functionalized Multi-Wall Carbon Nanotube and gold nanoparticles (AuNPs) were synthesized as biosensor electrodes. These materials have been applied to the detection of the Prostate Specific Antigen (PSA). The synthesis of AuNPs was carried out using polyvinylpyrrolidone (PVP) as protecting agent. The PVP/Au molar ratio (0.5 and 50) controls the nanoparticle size distribution, obtaining a wide and narrow distribution with an average diameter of 9.5 and 6.6 nm, respectively. Nanoparticle size distribution shows an important effect in the electrochemical performance of the biosensor, increasing the electrochemical active surface area (EASA) and promoting the electron-transfer from the redox probe (Ferrocene/Ferrocenium) to the electrode. Furthermore, a narrow and small nanoparticle size distribution enhances the amount of antibodies immobilized on the transducer material and the performance during the detection of the PSA. Significant results were obtained for the quantification of PSA, with a limit of detection of 1 ng·ml−1 and sensitivities of 0.085 and 0.056 μA·mL·ng−1 for the two transducer materials in only 5 min of detection. The authors would like to thank MINECO and FEDER (MAT2016-76595-R) for the financial support. AFQJ gratefully acknowledges Generalitat Valenciana for the financial support through Santiago Grisolia grant (GRISOLIA/2016/084).

The development and full-scale application of microbial electrochemical technologies (METs) for wastewater treatment demand massive amounts of electroconductive carbon materials to promote extracellular electron transfer (EET) and biodegradation. While the potential capability of these materials and their properties to design efficient systems is still in their infancy, the state-of-the-art METs are based on highly-conductive fossil-derived carbons. In this work we evaluate the performance of different electroconductive carbon materials (graphite, coke, biochar) for supporting microbial EET and treating urban wastewater. Our results reveal that the electroconductive biochar was the most efficient biofilter-material, enabling to stimulate bioremediation at anodic potential as high as 0.6 V (maximum removal efficiency (92%) and degradation rate (185 g-COD m−3d−1)), and to fulfill the discharge limits under conditions where the other materials failed. A deep materials characterization suggests that, despite electroconductivity is necessary, the optimal EET on biochar can be mainly assigned to its large number of electroactive surface oxygen functionalities, which can reversibly exchange electrons through the geobattery mechanism. We propose the modulation of quinone-like e-acceptors by anodic polarization to promote the biodegradation capability of carbon materials. Because of its great efficiency and sustainability, electroactive biochar will greatly expand the applicability of METs at large scale. This investigation has received funding from the European Union’s Horizon 2020 research and innovation programme under the grant agreement No. 642190 (Project “iMETLAND”; http://www.imetland.eu). Amanda Prado de Nicolás was funded by the “Formación de Personal Investigador (FPI)“ PhD fellowship programme from the University of Alcalá. The authors thank the MINECO and FEDER (IJCI-2014-20012) for financial support.

Clay material is used as a catalyst to degrade an organic pollutant,. This study focused on the O‐cresol oxidative degradation in aqueous solution by adding H2O2 and Mont‐Na. The catalytic tests showed a high catalytic activity of Mont‐Na, which made it possible to achieve more than 84.6% conversion after 90 minutes of reaction time at 55 °C in 23.2 mM H2O2. The pH value was found to be negatively correlated with the degradation rate of O‐cresol. UV‐Vis spectrophotometry revealed that the increase of degradation rate at low pH is related to the formation of 2‐Methylbenzoquinone as intermediate product. In addition, the content of iron in Mont‐Na decreased after the catalytic test, bringing further evidence about the O‐cresol catalytic oxidation. The mineralization of O‐cresol is also confirmed by the different methods of characterization of Mont‐Na after the catalytic oxidation test. The effect of the O‐cresol oxidation catalyzed by natural clay is significant. Financial support for this work by the Algerian Directorate General of Scientific Research and Technological Development (DGRSDT) and the Ministry for Higher Education and Scientific Research is gratefully appreciated.

[EN] The development of electrocatalysts based on the doping of copper over cobalt spinel supported on a microporous activated carbon has been studied. Both copper-cobalt and cobalt spinel nanoparticles were synthesized using a silica-template method. Hybrid materials consisting of an activated carbon (AC), cobalt oxide (Co3O4), and copper-doped cobalt oxide (CuCo2O4) nanoparticles, were obtained by dry mixing technique and evaluated as electrocatalysts in alkaline media for hydrogen evolution reaction. Physical mixtures containing 5, 10, and 20 wt.% of Co3O4 or CuCo2O4 with a highly microporous activated carbon were prepared and characterized by XRD, TEM, XPS, physical adsorption of gases, and electrochemical techniques. The electrochemical tests revealed that the electrodes containing copper as the dopant cation result in a lower overpotential and higher current density for the hydrogen evolution reaction., This research was funded by MINECO and FEDER (MAT2016-76595-R).

[EN] Electrochemical polymerization is known to be a suitable route to obtain conducting polymer-carbon composites uniformly covering the carbon support. In this work, we report the application of a filter-press electrochemical cell to polymerize polyaniline (PAni) on the surface of large-sized activated carbon cloth (ACC) by simple galvanostatic electropolymerization of an aniline-containing H2SO4 electrolyte. Flexible composites with different PAni loadings were synthesized by controlling the treatment time and characterized by means of Scanning Electron microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), physical adsorption of gases, thermogravimetric analysis (TGA), cyclic voltammetry and direct current (DC) conductivity measurements. PAni grows first as a thin film mostly deposited inside ACC micro- and mesoporosity. At prolonged electropolymerization time, the amount of deposited PAni rises sharply to form a brittle and porous, thick coating of nanofibrous or nanowire-shaped structures. Composites with low-loading PAni thin films show enhanced specific capacitance, lower sheet resistance and faster adsorption kinetics of Acid Red 27. Instead, thick nanofibrous coatings have a deleterious effect, which is attributed to a dramatic decrease in the specific surface area caused by strong pore blockage and to the occurrence of contact electrical resistance. Our results demonstrate that mass-production restrictions often claimed for electropolymerization can be easily overcome., This research was funded by Spanish Ministerio de Economia y Competitividad and FEDER funds, (grants MAT2016-76595-R and RYC-2017-23618) and Generalitat Valenciana (grant PROMETEO/2018/087)