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MXenes are the newest class of two-dimensional nanomaterials characterized by large surface area, high conductivity, and hydrophilicity. To further improve their performance for use in energy storage devices, heteroatoms or functional groups can be inserted into the Mxenes' structure increasing their stability. This work proposes insertion of lanthanum atoms into niobium-MXene (Nb-MX/La) that was characterized in terms of morphogy, structure, and electrochemical behavior. The addition of La to the Nb-MXene structure was essential to increase the spacing between the layers, improving the interaction with the electrolyte and enabling charge/discharge cycling in a higher potential window and at higher current densities. Nb-MX/La achieved a specific capacitance of up to 157 mF cm -2 , a specific capacity of 42 mAh cm -2 at 250 mV s -1 , a specific power of 37.5 mW cm -2 , and a specific energy of 14.1 mWh cm -2 after 1000 charge/discharge cycles at 50 mA cm -2 .

Design and development of novel, low-cost and efficient electrocatalysts for oxygen evolution reaction (OER) in alkaline media is crucial for lowering the reaction overpotential and thus decreasing the energy input during the water electrolysis process. Herein, we present the synthesis of new 14-membered bis-thiosemicarbazide and bis-isothiosemicarbazide macrocycles and their nickel(II) complexes characterized by spectroscopic techniques ( 1 H and 13 C NMR, IR, UV-vis), electrospray ionization mass spectrometry, single crystal X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) and cyclic voltammetry. Finally, the activity of nickel(II) complexes towards OER is reported. NiIILSEt delivered a current density of 10 mA cm -2 at the lowest overpotential of 350 mV with the lowest Tafel slope of 93 mV dec -1 . The high performance of NiIILSEt might be attributed to its high surface area and thus abundant active sites with the observed low charge-transfer resistance enabling the effective current flow through the electrocatalyst. Square-planar coordination geometry and increment in Ni oxidation state are believed to favor its OER performance. Beside high activity towards OER, NiIILSEt demonstrated excellent long-term stability with continuous operation, advocating its possible application in commercial systems.

In search for novel materials to replace noble metal-based electrocatalysts in electrochemical energy conversion and storage devices, special attention is given to a distinct class of materials, MAX phase that combines advantages of ceramic and metallic properties. Herein, Nb 4 AlC 3 MAX phase is prepared by a solid-state mixing reaction and characterized morphologically and structurally by transmission and scanning electron microscopy with energy-dispersive X-ray spectroscopy, nitrogen-sorption, X-ray diffraction analysis, X-ray photoelectron and Raman spectroscopy. Electrochemical performance of Nb 4 AlC 3 in terms of capacitance as well as for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is evaluated in different electrolytes. The specific capacitance C s of 66.4, 55.0, and 46.0 F g -1 at 5 mV s -1 is determined for acidic, neutral and alkaline medium, respectively. Continuous cycling reveals high capacitance retention in three electrolyte media; moreover, increase of capacitance is observed in acidic and neutral media. The electrochemical impedance spectroscopy showed a low charge transfer resistance of 64.76 Ω cm 2 that resulted in better performance for HER in acidic medium (Tafel slope of 60 mV dec -1 ). In alkaline media, the charge storage value in the double layer is 360 mF cm -2 (0.7 V versus reversible hydrogen electrode) and the best ORR performance of the Nb 4 AlC 3 is achieved in this medium (Tafel slope of 126 mV dec -1 )., (© 2024 Wiley‐VCH GmbH.)

Oxygen evolution reaction (OER) electrocatalysts are frequently made from noble metal-based oxides like ruthenium/iridium oxides. However, because of their scarcity and high price, researchers are now focusing on creating innovative OER catalysts based on affordable transition metals that have improved electrical conductivity and accessibility to active sites. Metal-organic frameworks (MOFs), a unique class of inorganic materials with excellent physical and chemical properties, have witnessed significant progress in promising green energy systems. In this work, a novel mixed-ligand metal-organic framework [Co(μ-1κ N ,2κ N '-BDP)(μ 3 -1κoo',2κo''2κo'''-BTC)] n · n H 2 O (BDP = boron-dipyrromethene or BODIPY; BTC = benzene tricarboxylate) denoted as CoBDPMOF has been synthesized, and its composites with different carbon materials have been designed. Compared to the pristine MOF, the composites showed enhanced electrocatalytic activity toward the oxygen evolution reaction (OER) in alkaline media. In addition, the CoBDPMOF with activated carbon showed the highest OER performance with a low Tafel slope (82 mV dec -1 ) and the highest j 600 (59.8 mA cm -2 ), outperforming noble metal IrO 2 , the OER benchmark electrocatalyst. This study presents new insights into the design and application of CoBDPMOF-based materials for energy conversion and suggests promising avenues for further research and development in electrocatalysis.

For the first time, composites of metal-organic framework MOF-5 and conjugated polymer polyaniline (PANI), (MOF-5/PANI), prepared using PANI in its conducting (emeraldine salt, ES) or nonconducting form (emeraldine base, EB) at various MOF-5 and PANI mass ratios, were evaluated as electrode materials for the electrochemical detection of cadmium (Cd 2+ ) and lead (Pb 2+ ) ions in aqueous solutions. Testing of individual components of composites, PANI-ES, PANI-EB, and MOF-5, was also performed for comparison. Materials are characterized by Raman spectroscopy, scanning electron microscopy (SEM) and dynamic light scattering (DLS), and their electrochemical behavior was discussed in terms of their zeta potential, structural, morphology, and textural properties. All examined composites showed high electrocatalytic activity for the oxidation of Cd and Pb to Cd 2+ and Pb 2+ , respectively. The MOF/EB-1 composite (71.0 wt.% MOF-5) gave the highest oxidation currents during both individual and simultaneous detection of two heavy metal ions. Current densities recorded with MOF/EB-1 were also higher than those of its individual components, reflecting the synergistic effect where MOF-5 offers high surface area for two heavy metals adsorption and PANI offers a network for electron transfer during metals' subsequent oxidation. Limits of detection using MOF/EB-1 electrode for Cd 2+ and Pb 2+ sensing were found to be as low as 0.077 ppm and 0.033 ppm, respectively. Moreover, the well-defined and intense peaks of Cd oxidation to Cd 2+ and somewhat lower peaks of Pb oxidation to Pb 2+ were observed at voltammograms obtained for the Danube River as a real sample with no pretreatment, which implies that herein tested MOF-5/PANI electrodes could be used as electrochemical sensors for the detection of heavy metal ions in the real water samples.

Direct liquid fuel cells (DLFCs) operate directly on liquid fuel instead of hydrogen, as in proton-exchange membrane fuel cells. DLFCs have the advantages of higher energy densities and fewer issues with the transportation and storage of their fuels compared with compressed hydrogen and are adapted to mobile applications. Among DLFCs, the direct borohydride-hydrogen peroxide fuel cell (DBPFC) is one of the most promising liquid fuel cell technologies. DBPFCs are fed sodium borohydride (NaBH 4 ) as the fuel and hydrogen peroxide (H 2 O 2 ) as the oxidant. Introducing H 2 O 2 as the oxidant brings further advantages to DBPFC regarding higher theoretical cell voltage (3.01 V) than typical direct borohydride fuel cells operating on oxygen (1.64 V). The present review examines different membrane types for use in borohydride fuel cells, particularly emphasizing the importance of using bipolar membranes (BPMs). The combination of a cation-exchange membrane (CEM) and anion-exchange membrane (AEM) in the structure of BPMs makes them ideal for DBPFCs. BPMs maintain the required pH gradient between the alkaline NaBH 4 anolyte and the acidic H 2 O 2 catholyte, efficiently preventing the crossover of the involved species. This review highlights the vast potential application of BPMs and the need for ongoing research and development in DBPFCs. This will allow for fully realizing the significance of BPMs and their potential application, as there is still not enough published research in the field.

Oxygen evolution reaction (OER) represents the efficiency-limiting reaction in water electrolyzers, metal-air batteries, and unitized regenerative fuel cells. To achieve high-efficiency OER in alkaline media, we fabricated three novel electrocatalysts by the assembly of as-prepared Co 45 Pt 55 alloy nanoparticles (NPs) on three different carbon-based support materials: reduced graphene oxide (CoPt/rGO), mesoporous graphitic carbon nitride (CoPt/mpg-CN), and commercial Ketjenblack carbon (CoPt/KB). Voltammetry studies revealed that CoPt/rGO electrocatalyst provided lower OER overpotentials accompanied by higher currents and specific current density values than the other two studied materials. Moreover, CoPt/rGO outperformed commercial CoPt/C electrocatalysts in terms of notably higher specific current densities. Additionally, it was found that CoPt/rGO electrocatalyst activity increases with increasing temperature up to 85°C, as suggested by the increase in the exchange current density. Electrochemical impedance spectroscopy studies of three electrocatalysts in OER revealed similar charge transfer resistance, although CoPt/rGO provided a higher current density. The main issue observed during long-term chronoamperometry and chronopotentiometry studies is the materials' instability under OER polarization conditions, which is still to be tackled in future work., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Andrić, Milikić, Sevim, Santos and Šljukić.)

A set of platinum (Pt) and earth-abundant transition metals (M = Ni, Fe, Cu) on graphene nanoplatelets (sqPtM/GNPs) was synthesised via sequential deposition to establish parallels between the synthesis method and the materials' electrochemical properties. sqPtM/GNPs were assessed as bifunctional electrocatalysts for oxygen evolution (OER) and reduction (ORR) reactions for application in unitised regenerative fuel cells and metal-air batteries. sqPtFe/GNPs showed the highest catalytic performance with a low potential difference of ORR half-wave potential and overpotential at 10 mA cm -2 during OER, a crucial parameter for bifunctional electrocatalysts benchmarking. A novel two-stage synthesis strategy led to higher electrocatalytic performance by facilitating the reactants' access to the active sites and reducing the charge-transfer resistance.

Depletion of non-renewable fuel has obliged researchers to seek out sustainable and environmentally friendly alternatives. Membranes have proven to be an effective technique in biofuel production for reaction, purification, and separation, with the ability to use both porous and non-porous membranes. It is demonstrated that a membrane-based sustainable and green production can result in a high degree of process intensification, whereas the recovery and repurposing of catalysts and alcohol are anticipated to increase the process economics. Therefore, in this study sustainable biodiesel was synthesized from inedible seed oil (37 wt%) of Cordia myxa using a membrane reactor. Transesterification was catalyzed by heterogenous nano-catalyst of indium oxide prepared with leaf extract of Boerhavia diffusa. Highest biodiesel yield of 95 wt% was achieved at methanol to oil molar ratio of 7:1, catalyst load 0.8 wt%, temperature 82.5 °C and time 180 min In 2 O 3 nanoparticles exhibited reusability up to five successive transesterification rounds. The production of methyl esters was confirmed using Fourier-transform infrared spectroscopy and Nuclear Magnetic Resonance. The predominant fatty acid methyl ester detected in the biodiesel was 5, 8-octadecenoic acid. Biodiesel fuel qualities were determined to be comparable to worldwide ASTM D-6571 and EN-14214 standards. Finally, it was concluded that membrane technology can result in a highly intensified reaction process while efficient recovery of both nano catalysts and methanol increases the economics of transesterification and lead to sustainable production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The new 3D coordination polymer (CP) [Mn(L)(HCOO)] n ( Mn-CP ) [L = 4-(pyridin-4-ylcarbamoyl)benzoate] was synthesised via a hydrothermal reaction using the pyridyl amide functionalized benzoic acid HL. It was characterized by elemental, FT-IR spectroscopy, single-crystal and powder X-ray diffraction (PXRD) analyses. Its structural features were disclosed by single-crystal X-ray diffraction analysis, which revealed a 3D structure with the monoclinic space group P21/c. Its performance as an electrocatalyst for oxygen reduction (ORR), oxygen evolution (OER), and hydrogen evolution (HER) reactions was tested in both acidic (0.5 M H 2 SO 4 ) and alkaline (0.1 M KOH) media. A distinct reduction peak was observed at 0.53 V vs. RHE in 0.1 M KOH, which corresponds to the oxygen reduction, thus clearly demonstrating the material's activity for the ORR. Tafel analysis revealed a Tafel slope of 101 mV dec -1 with mixed kinetics of 2e - and 4e - pathways indicated by the Koutecky-Levich analysis. Conversely, the ORR peak was not present in 0.5 M H 2 SO 4 indicating no activity of Mn-CP for this reaction in acidic media. In addition, Mn-CP demonstrated a noteworthy activity toward OER and HER in acidic media, in contrast to what was observed in 0.1 M KOH.

The mixed ionic-electronic conducting (MIEC) oxides have generated significant research efforts in the scientific community during the last 40 years. Since then, many MIEC compounds, most of which are based on perovskite oxides, have been synthesized and characterized. These compounds, when heated to high temperatures, form solid ceramic membranes with high oxygen ionic and electrical conductivity. The driving force for oxygen ion transport is the ionic transfer of oxygen from the air as a result of the differential partial pressure of oxygen across the membrane. Electronic and ionic transport in a range of MIEC materials has been studied using the defect theory, particularly when dopants are introduced to the compound of interest. As a result, many types of ionic oxygen transport limits exist, each with a distinct phase shift depending on the temperature and partial pressure of oxygen in use. In combination with theoretical principles, this work attempts to evaluate the research community's major and meaningful achievements in this subject throughout the preceding four decades., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Six cobalt gold (CoAu) electrodes were prepared by electroless deposition using different gold-containing solutions (acidic and weakly acidic) and different Au deposition times. Characterization of CoAu electrodes was done by scanning electron microscopy with energy-dispersive X-ray spectroscopy, N 2 -sorption, and X-ray powder diffraction techniques. The possibility of using the prepared electrodes in environmental applications, i.e. , for the electrochemical sensing of a trace amount of arsenic(iii) in weakly alkaline media was assessed. Employing the CoAu electrode (prepared by immersing Co/Cu into 1 mM HAuCl 4 (pH 1.8) at 30 °C for 30 s) under optimized conditions (deposition potential -0.7 V and deposition time of 60 s), a low limit of detection of 2.16 ppb was obtained. Finally, this CoAu electrode showed activity for arsenic oxidation in the presence of Cu(ii) as a model interferent as well as in real samples. Furthermore, the use of CoAu electrode as an anode in fuel cells, namely, direct borohydride - hydrogen peroxide fuel cells was also assessed. A peak power density of 191 mW cm -2 was attained at 25 °C for DBHPFC with CoAu anode at a current density of 201 mA cm -2 and cell voltage of 0.95 V, respectively. The peak power density further increased with the increase of the operating temperature to 55 °C., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Copper-silver and cobalt-silver alloy nanoparticles deposited on reduced graphene oxide (CuAg/rGO and CoAg/rGO) were synthesized and examined as electrocatalysts for oxygen reduction reaction (ORR) and hydrogen peroxide reduction reaction (HPRR) in alkaline media. Characterization of the prepared samples was done by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction analysis (XRD), and scanning electron microscopy with integrated energy-dispersive X-ray spectroscopy (SEM-EDS). CuAg/rGO and CoAg/rGO nanoparticles diameter ranged from 0.4 to 9.2 nm. The Ag loading was ca. 40 wt.% for both electrocatalysts, with that for Cu and Co being 35 and 17 wt.%, respectively. CoAg/rGO electrocatalyst showed a Tafel slope of 109 mV dec -1 , significantly lower than that for CuAg/rGO (184 mV dec -1 ), suggesting faster ORR kinetics. Additionally, a higher diffusion current density was obtained for CoAg/rGO (-2.63 mA cm -2 ) than for CuAg/rGO (-1.74 mA cm -2 ). The average value of the number of electrons transferred during ORR was 2.8 for CuAg/rGO and 3.3 for CoAg/rGO electrocatalyst, further confirming the higher ORR activity of the latter. On the other hand, CuAg/rGO showed higher peak current densities (-3.96 mA cm -2 ) for HPRR compared to those recorded for CoAg/rGO electrocatalyst (-1.96 mA cm -2 ).

Platinum-dysprosium (Pt-Dy) alloys prepared by the arc melting technique are assessed as potential electrodes for the oxygen reduction reaction (ORR) using voltammetry and chronoamperometry in alkaline media. A relatively small change (10 at.%) in the alloy composition brought a notable difference in the alloys' performance for the ORR. Pt 40 Dy 60 electrode, i.e., the electrode with a lower amount of Pt, was identified to have a higher activity towards ORR as evidenced by lower overpotential and higher current densities under identical experimental conditions. Furthermore, DFT calculations point out the unique single-atom-like coordination and electronic structure of Pt atoms in the Pt 40 Dy 60 surface as responsible for enhanced ORR activity compared to the alloy with a higher Pt content. Additionally, Pt-Dy alloys showed activity in the oxygen evolution reaction (OER), with the OER current density lower than that of pure Pt.

β-Ni(OH) 2 nanoplatelets are prepared by a hydrothermal procedure and characterized by scanning and transmission electron microscopy, X-ray diffraction analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. The material is demonstrated to be an efficient electrocatalyst for oxygen reduction, oxygen evolution, and hydrogen evolution reactions in alkaline media. β-Ni(OH) 2 shows an overpotential of 498 mV to reach 10 mA cm -2 towards oxygen evolution, with a Tafel slope of 149 mV dec -1 (decreasing to 99 mV dec -1 at 75 °C), along with superior stability as evidenced by chronoamperometric measurements. Similarly, a low overpotential of -333 mV to reach 10 mA cm -2 (decreasing to only -65 mV at 75 °C) toward hydrogen evolution with a Tafel slope of -230 mV dec -1 is observed. Finally, β-Ni(OH) 2 exhibits a noteworthy performance for the ORR, as evidenced by a low Tafel slope of -78 mV dec -1 and a number of exchanged electrons of 4.01 (indicating direct 4e - -oxygen reduction), whereas there are only a few previous reports on modest ORR activity of pure Ni(OH) 2 ., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The synthesis of palladium-based trimetallic catalysts via a facile and scalable synthesis procedure was shown to yield highly promising materials for borohydride-based fuel cells, which are attractive for use in compact environments. This, thereby, provides a route to more environmentally friendly energy storage and generation systems. Carbon-supported trimetallic catalysts were herein prepared by three different routes: using a NaBH 4 -ethylene glycol complex (PdAuNi/C SBEG ), a NaBH 4 -2-propanol complex (PdAuNi/C SBIPA ), and a three-step route (PdAuNi/C 3-step ). Notably, PdAuNi/C SBIPA yielded highly dispersed trimetallic alloy particles, as determined by XRD, EDX, ICP-OES, XPS, and TEM. The activity of the catalysts for borohydride oxidation reaction was assessed by cyclic voltammetry and RDE-based procedures, with results referenced to a Pd/C catalyst. A number of exchanged electrons close to eight was obtained for PdAuNi/C 3-step and PdAuNi/C SBIPA (7.4 and 7.1, respectively), while the others, PdAuNi/C SBEG and Pd/C SBIPA , presented lower values, 2.8 and 1.2, respectively. A direct borohydride-peroxide fuel cell employing PdAuNi/C SBIPA catalyst in the anode attained a power density of 47.5 mW cm -2 at room temperature, while the elevation of temperature to 75 °C led to an approximately four-fold increase in power density to 175 mW cm -2 . Trimetallic catalysts prepared via this synthesis route have significant potential for future development.

A detailed examination of the principle of operation behind the functioning of the full-self-powered humidity sensor is presented. The sensor has been realized as a structure consisting of an interdigitated capacitor with aluminum thin-film digits. In this work, the details of its fabrication and activation are described in detail. The performed XRD, FTIR, SEM, AFM, and EIS analyses, as well as noise measurements, revealed that the dominant process of electricity generation is the electrochemical reaction between the sensor's aluminum electrodes and the water from humid air in the presence of oxygen, which was the main goal of this work. The response of the sensor to human breath is also presented as a demonstration of its possible practical application.

Bimetallic cobalt (Co)-based coatings were prepared by a facile, fast, and low-cost electroless deposition on a copper substrate (CoFe, CoMn, CoMo) and characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction analysis. Prepared coatings were thoroughly examined for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution (1 M potassium hydroxide, KOH) and their activity compared to that of Co and Ni coatings. All five coatings showed activity for both reactions, where CoMo and Co showed the highest activity for HER and OER, respectively. Namely, the highest HER current density was recorded at CoMo coating with low overpotential (61 mV) to reach a current density of 10 mA·cm -2 . The highest OER current density was recorded at Co coating with a low Tafel slope of 60 mV·dec -1 . Furthermore, these coatings proved to be stable under HER and OER polarization conditions.

The new 2D coordination polymers (CPs) [M(L) 2 (H 2 O) 2 ] n [M = Co II ( 1 ) and Ni II ( 2 ); L = 4-(pyridin-3-ylcarbamoyl)benzoate] were synthesized from pyridyl amide-functionalized benzoic acid ( HL ). They were characterized by elemental, Fourier transform infrared, thermogravimetric, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction (XRD) structural analyses. Single-crystal XRD analysis revealed the presence of a 2D polymeric architecture, and topological analyses disclose a 2,4-connected binodal net. A thermochromic effect leads to the production of two new CPs, 1' and 2' , by heating at ca. 220 °C, accompanied by a color change from orange to purple in the case of 1 and from blue to green in the case of 2 . The transformation of 1 to 1' takes place through an intermediate ( 1a ) with a different twist of the L - ligand, leading to the formation of a 1D polymeric architecture, as proven by single-crystal XRD analysis. The addition of water or keeping 1' or 2' in air for several days leads to regeneration of 1 or 2 , respectively. The thermochromic-triggered structural transformations of 1 and 2 were further substantiated by PXRD and UV-vis ground-state diffuse-reflectance absorption studies. The supercapacitance ability of the CPs 1 and 2 and a Ni-Co composite (made from mixing the CPs 1 and 2 ) was investigated by electroanalytical techniques, such as cyclic voltammetry and electrochemical impedance spectroscopy. The CP 2 exhibits the highest specific capacity of 273.8 C g -1 at an applied current density of 1.5 A g -1 . These newly developed CPs further act as electrocatalysts for the water-splitting reaction.

Molybdenum carbide (Mo 2 C)-based electrocatalysts were prepared using two different carbon supports, commercial carbon nanotubes (CNTs) and synthesised carbon xerogel (CXG), to be studied from the point of view of both capacitive and electrocatalytic properties. Cation type (K + or Na + ) in the alkaline electrolyte solution did not affect the rate of formation of the electrical double layer at a low scan rate of 10 mV s -1 . Conversely, the different mobility of these cations through the electrolyte was found to be crucial for the rate of double-layer formation at higher scan rates. Molybdenum carbide supported on carbon xerogel (Mo 2 C/CXG) showed ca. 3 times higher double-layer capacity amounting to 75 mF cm -2 compared to molybdenum carbide supported on carbon nanotubes (Mo 2 C/CNT) with a value of 23 mF cm -2 due to having more than double the surface area size. The electrocatalytic properties of carbon-supported molybdenum carbides for the oxygen reduction reaction in alkaline media were evaluated using linear scan voltammetry with a rotating disk electrode. The studied materials demonstrated good electrocatalytic performance with Mo 2 C/CXG delivering higher current densities at more positive onset and half-wave potential. The number of electrons exchanged during oxygen reduction reaction (ORR) was calculated to be 3, suggesting a combination of four- and two-electron mechanism.

Monitoring bromides (Br - ) is of crucial importance since bromates, potential human carcinogens, are formed during ozonation of water containing bromides in concentrations >100  μ g L -1 . Within this study, silver (Ag) and four carbon-supported Ag catalysts were synthesized by the γ -radiation method and their morphology and structure examined using transmission electron microscopy, X-ray diffraction, and UV-Vis analysis. The nanocatalysts were tested for Br - sensing in aqueous media using cyclic voltammetry. All five Ag materials exhibited electroactivity for sensing of Br - ions, with pure Ag catalyst giving the best response to Br - ions presence in terms of the lowest limit of detection. Sensing of bromides was also explored in tap water after addition of bromides suggesting that herein prepared catalysts could be used for bromides detection in real samples. Furthermore, sensing of other halogen ions, namely, chlorides and iodides, was examined, and response due to chloride presence was recorded.

Low-cost molybdenum carbide (Mo2 C) nanoparticles supported on carbon nanotubes (CNTs) and on carbon xerogel (CXG) were prepared and their activity for the hydrogen evolution reaction (HER) was evaluated in 8 m KOH aqueous electrolyte at 25-85 °C. Measurements of the HER by linear scan voltammetry allowed us to determine Tafel slopes of 71 and 74 mV dec(-1) at 25 °C for Mo2 C/CNT and Mo2 C/CXG, respectively. Stability tests were also performed, which showed the steady performance of the two electrocatalysts. Moreover, the HER kinetics at Mo2 C/CNT was enhanced significantly after the long-term stability tests. The specific activity of both materials was high, and a higher stability was obtained for the activated Mo2 C/CNT (40 A g(-1) at -0.40 V vs. the reversible hydrogen electrode)., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Graphite modified with gallic acid to form 'gallic acid-carbon' is demonstrated to be efficient for the removal of bismuth(III) ions from aqueous solutions. The uptake is demonstrated to be rapid but not to follow standard adsorption isotherm models. Instead, the uptake was found to be further promoted by the presence of the adsorbed metal. Additionally, the bismuth uptake showed linear dependence on the square of its concentration suggesting the possible formation of polymeric bismuth species. The gallic acid-carbon shows great promise as a relatively inexpensive material for solid-phase extraction and water purification with extraction efficiency close to 98%.

Manganese dioxide screen printed graphite electrodes for electro-analytical sensing purposes have been fabricated. The prepared sensors exhibit attractive performances as electro-catalysts for the sensing of nitrite ions and ascorbic acid with detection limits comparable or lower than those obtainable with other electrochemical sensors. The manganese dioxide platforms are also explored towards the electrochemical reduction of oxygen which has importance in electrochemical energy storage. While the platforms are found to operate by a four-electron reduction producing water (rather than hydrogen peroxide which is undesirable), a large overpotential, compared to other possible electrode compositions reported in the literature, is required. Nevertheless, the promising results towards the electro-analytical sensing of nitrite ions and ascorbic acid and also given the disposable nature and scale of economies make these electrodes useful as sensor platforms.