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Commercial polymer electrolyte membrane fuel cells have relied on scares Platinum to catalyse the kinetically sluggish oxygen reduction reaction occurring at their anodes. Over the last decade organic materials, frequently based on graphitic structures have been demonstrated as promising alternative electrocatalysts to the noble metals. Researchers typically utilize ultrasonic treatment as part of the synthesis procedure to achieve homogeneous dispersion of graphitic carbon prior to. Herein we investigate the implications of the structural and compositional changes induced by the ultrasonication treatment on boron-doped reduced graphene oxide for oxygen reduction reaction. It is shown that ultrasonication pre-treatment prior to the boron doping and reduction of graphene oxide via hydrothermal process step leads to the increase of both substitutional B and electrocatalytic surface area, with associated reduction of average pore size diameter, leading to a significant improvement in the oxygen reduction reaction performance, with respect to the non-ultrasonicated material. It is proposed that the higher degree of substitutional doping of boron is a result of formation of the additional epoxy functionalities on graphitic planes, which act as a doping site for boric acid. • Ultrasonication enables higher doping of boron into Graphene oxide. • Longer ultrasonication times leads to higher substitutional boron. • Longer ultrasonication times leads to higher ORR activity. [ABSTRACT FROM AUTHOR]

We report the influence of structural features on the properties of porous carbonaceous materials obtained using soft-templating coupled with hydrothermal carbonisation. Our results demonstrate that using d - glucose with Pluronic P123 results in a more homogeneous particle size distribution of carbon spheres compared with d - fructose. The textural properties of the carbon materials, both surface area and pore volume, have improved when the carbonisation temperature was increased from 550 °C to 900 °C, while the amount of C C bonds was also increased. Physical activation with CO 2 was found to open the pores and thereby improve textural properties, including total pore volume, micropore volume, and surface area. Concomitantly, the CO 2 and H 2 S uptake also underwent significant enhancement, achieving a maximum CO 2 adsorption capacity of 8.37 mmol/g at 0 °C and 1 bar, and ca. 6 mmol/g at room temperature and 1 bar. The same samples showed about 25.7 mmol/g adsorption capacity for H 2 S at room temperature and atmospheric pressure, with approximately 32% process efficiency. Image 1 • Soft templating strategy coupled with hydrothermal carbonisation (HTC) resulted in improved porosity. • The highest CO 2 uptake has been obtained after physical activation. • H 2 S adsorption efficiency was boosted after physical activation step. [ABSTRACT FROM AUTHOR]

After being undervalued for a long-time, the potential use of lignins have gained interest as a source of wealth from waste. Despite the complexity of lignins chemical structure, its high carbon content compared to cellulose and sugars makes lignin a very promising precursor for the development of nanocarbons for broad range applications, including supercapacitors for energy storage. High performing supercapacitors have been made using dimensionally different nanocarbon entities (zero-to three), such as carbon nanoparticles, carbon nanodots, carbon fibers, and carbon nanosheets with modular and interconnected pore structures, which are prepared from lignins of various types with and without use of templates, porogens and chemical agents. Control of physicochemical and electrochemical properties in such nanocarbons remains the key for their high energy density, flexibility, and long-term stability. To this end, nanocarbons conductivity, porosity and surface areas are controlled by various synthesis approaches while detailed adjustment of pore structure, pore width and pore distribution have been made to improve electrolyte access, ions confinement, and transportation. To compare performances of nanocarbons made from different lignin types, we must do meaningful investigations on the lignin's structure, composition, and purity to understand how their structure-property relationships are influenced by pyrolysis, carbonization and activation methods/conditions used. In this review, a clear overview of the lignins structure, classification, and properties is presented, wherein we compared the structure-property-performance relationships of nanostructured carbons from lignins for improvement of supercapacitor device performances with recent advances. Separation processes of lignin from wood, steps involved in preparing dimensionally different nanocarbon entities (zero -to three), and electrolytes for the fabrication of sustainable and flexible supercapacitor devices. [Display omitted] [ABSTRACT FROM AUTHOR]

The next generation of proton exchange membrane fuel cells (PEMFCs) require a substantial reduction or elimination of Pt-based electrocatalyst from the cathode, where O 2 reduction takes place. The most promising alternative to Pt is atomic Fe embedded in N-doped C (Fe–N–C). Successful incorporation of Fe–N–C in PEMFCs relies on a thorough understanding of the catalyst layer properties, both ex situ and in situ , with tailored electrode interface engineering. To help resolve this conundrum, we provide a quantitative protocol on the optimisation of I/C for Fe–N–Cs. It is demonstrated that a high pore volume (3.33 cm3 g−1 FeNC) Fe–N–C catalyst requires a sufficiently high ionomer to catalyst mass ratio (I/C, 2.8≤I/C ≤ 4.2) for optimum PEMFC activity under H 2 /O 2. Emerging electrochemical techniques (distribution of relaxation times and Fourier transformed alternating current voltammetry) were used to deconvolute for the first time the trade-off between proton and electron resistance and accessible FeN x active site density with increasing ionomer loading. These findings highlight the significant impact of tuning the I/C ratio based on the catalyst layer properties and feature the power of evolving electrochemical tools for optimising performance in PEMFCs and other electrochemical devices. [Display omitted] • In situ FTacV quantified Fe–N–C electrochemical active site density in fuel cell. • Fe–N–C active site density and current density correlated with ionomer loading. • DRT quantified resistance to proton transport and oxygen diffusion in fuel cell. • Fe–N–C to ionomer ratio optimised based on quantitative protocol. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hydrothermal processes avoid the energy intensive step of biomass drying. [•] Hydrogen or methane can be formed throughout hydrothermal biomass gasification. [•] Hydrothermal liquefaction produces oils with a high heating value. [•] Lignin can be hydrothermally liquefied to valuable chemicals. [•] Hydrothermal carbonization produces biochars and other interesting materials. [ABSTRACT FROM AUTHOR]

Abstract: One of the recent major improvements of HPLC was the introduction of monolithic silica columns, which have the advantage of faster separation and lower back pressure as compared to common silica beads. Here, we present an interesting alternative to such reversed-phase monolithic columns by a convenient coupling route of a thermo-responsive polymer to hydrophilic silica monoliths. Poly(N-isopropylacrylamide) (PNIPAM) was polymerized in solution via a reversible addition fragmentation chain transfer (RAFT) polymerization technique and coupled then in situ onto an amino-modified silica monolithic column. These columns were compared with RP-18 monolithic columns in the separation of steroids under isocratic condition in aqueous mobile phase. Separation is optimized just by changing the temperature, instead of changing the mobile phase composition. [Copyright &y& Elsevier]

Alkali metal ion batteries are instrumental in the widespread implementation of electric vehicles, portable electronics, and grid energy storage. From experimental characterisation of hard carbons, these carbon anodes were shown to contain a variety of functional groups. Through density functional theory simulations, the effect of functional groups (O, OH, NH 2 , and COOH) on edges and basal plane surfaces of carbonaceous materials on the adsorption of lithium, sodium, and potassium are investigated. These simulations show that the functionalisation of H-terminated edges and curved surfaces rather than basal planes is more energetically favourable and thus more likely to be present. Comparison of experimental FTIR and computational vibrational frequency analysis confirmed the occurrence of the investigated functional groups (O, OH, NH 2 , and COOH) in the synthesised hard carbon materials. Metal adsorption on the functionalised models showed that adsorption energies were stronger on the functionalised basal plane in comparison to the functionalised edge sites and contribute to the metal ion immobilization and consequent irreversible capacity loss. The metal adsorption on the curved surface was further improved by the addition of functional groups, benefitting the initial lithiation/sodiation/potassiation of the carbon anode. Hence, the morphology of the functionalised carbon systems plays an important role in the charge/discharge performance of carbonaceous anodes. [Display omitted] • XPS and FTIR identify functional groups in hard carbon. • Functional groups can adsorb at different carbon motifs. • DFT simulations show that functional groups bind strongly to edge sites. • Li, Na, and K bind strongly to hydroxyl groups. • Functional group type and site play important roles in the charge/discharge process. [ABSTRACT FROM AUTHOR]

Pyridinic-N configurations and intrinsic defects on nanocarbons have been regarded as potentially active-sites for the oxygen reduction reaction (ORR). In this work, a facile strategy is demonstrated to achieve pyridinic-N dominated porous carbon nanosheets with edge-enriched defective nature through the selection of the bio-precursor guanine as C/N sources. It is able to achieve high contents of pyridinic-N dominated (48.1% from gross N) species and the few-layers carbon architectures with hierarchical porosity by a template-free carbonization method. These 2D carbon structures are of low cost, scalable and economically attractive while based on renewable and highly abundant resources. As a result, the optimized catalyst delivers a significantly enhanced electrocatalytic performance for ORR under wide range of pH from alkaline to acid, i. e. possessing a 30 mV more positive half-wave potential (0.885 V) than Pt/C (0.855 V) catalyst in 0.1 M KOH, and very close activities to Pt/C in 0.1 M PBS and 0.1 M HClO 4 solution. This ORR performance is attributed to the synergistic effects of unique graphene-like architecture, high porosity, and coexistences of high contents of pyridinic-N species and abundant edge/defect sites. Image 1 A facile strategy is demonstrated to achieve pyridinic-N dominated porous carbon nanosheets with edge-enriched defective nature through the selection of the biological nucleobase precursor as C/N sources. [ABSTRACT FROM AUTHOR]

The regenerative hydrogen/vanadium fuel cell (RHVFC) is investigated with Freudenberg carbon paper electrodes (CPs). Along with thermal treatment, the Freudenberg CPs are also treated with reduced graphene oxide (rGO) using electrophoretic deposition at 300 V. The rGO modified CP results in 25% higher power density than its untreated counterpart under the same operating conditions. In comparison to the first preliminary study, the power density reported herein is more than four times higher. Additionally, the Freudenberg CPs modified with heat treatment followed by rGO deposition facing the membrane (rGOHTFM) provide the best electrolyte discharge utilization (UE) of 99%, followed by untreated (98%) and heat treated samples (97%) at 50 mA cm−2. The rGOHTFM also record high charge and discharge energy efficiencies (η E) of 93% at the same current density, which is slightly higher than untreated CPs (η E = 91%). Cycling the system 10 times also results in higher η E and UE for rGOHTFM CP (η E = 92% and UE = 99% on average) in comparison to untreated electrodes (η E = 86% and UE = 97% on average). In comparison the widely investigated SGL 10AA CP has lower efficiencies and utilization as expected (η E = 74% and UE = 83% on average). Image 1 • Freudenberg carbon paper electrodes are studied in hydrogen/vanadium fuel cell. • Freudenberg electrodes give much better charge/discharge response to SGL 10AA. • Untreated samples have similar performance to rGO modified ones at 50 mA cm−2. • Reduced graphene oxide modification of heat treated samples gave best results. • High cycling efficiencies (92%) and electrolyte utilization (99%) are reported. [ABSTRACT FROM AUTHOR]

Pure eucalyptus Kraft lignin derived carbon fiber mats were produced based on a model workflow. It covers the preparation and characterization of the lignin precursor and the carbon materials and its testing in the final application (supercapacitor). Sequential solvent extraction was employed to produce a eucalyptus Kraft lignin precursor which could be electrospun into lignin fibers without any additives. The fiber formation from low molecular weight lignin is assigned to strong intermolecular interactions via hydrogen bonding and π-π-stacking between individual lignin macromolecules which gives rise to association complexes in the electrospinning solution. By stabilization in air, carbonization in N 2 and an activation step in CO 2 , free-standing microporous carbon fiber mats could be produced. These fiber mats possess mainly basic oxygen functional groups which proved to be beneficial when tested as free-standing electrodes in symmetric supercapacitors. Consequently, the CO 2 -activated fiber mats showed a high specific gravimetric capacitance of 155 F/g at 0.1 A/g, excellent rate capability with 113 F/g at 250 A/g and good capacitance retention of 94% after 6000 cycles when tested in 6 M KOH electrolyte. Therefore, we conclude that lignin itself is a promising precursor to produce microporous, oxygen functionalized carbon fibers serving as free-standing electrodes in aqueous supercapacitors. Image 1 [ABSTRACT FROM AUTHOR]

Abstract In order to compensate for cracking, brittleness and low electrical conductivity of polymer-derived silicon oxycarbide (SiOC), graphene was successfully introduced into a SiOC matrix by phase transfer of graphene oxide (GO) from an aqueous (GO dispersed in water) to organic phase (copolymer as SiOC precursor in diethyl ether). Spark plasma sintering (SPS) was used to fully densify composites to ∼2.3g/cm3. The prepared materials were comprehensively characterized and exhibited significant enhancement in the mechanical properties, electrical conductivity and electrochemical performance. Self-assembled lamellar structure of graphene in the SiOC-matrix was achieved, leading to anisotropy in the properties of the composites. The fracture toughness of the SiOC-2vol%GO composite was increased by ∼91%, at the expense of a slight decrease in the flexural strength, compared to the SiOC-matrix. Moreover, the composites exhibited three orders higher electrical conductivity than the SiOC-matrix. The electrical conductivity in the perpendicular direction (σ ┴ = 3 × 10−1S/cm) of SiOC-2vol%GO composites was two orders of magnitude higher than that in the parallel direction (σ ‖ = 4.7 × 10−3S/cm), owing to the self-assembled lamellar graphene in the SiOC-matrix. The SiOC-2vol%GO composites further showed better electrochemical performance of oxygen reduction reaction (ORR) than pure graphene, exhibiting an onset potential (∼0.75 V vs RHE) and more positive half-wave potential (∼0.6 V vs RHE). Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

This work considers the relationship between the morphology of porous carbon materials used for supercapacitors and the electrochemical impedance spectroscopy (EIS) response. EIS is a powerful tool that can be used to study the porous 3-dimensional electrode behavior in different electrochemical systems. Porous carbons prepared by treatment of cellulose with different compositions of potassium hydroxide (KOH) were used as model systems to investigate the form vs. electrochemical function relationship. A simple equivalent circuit that represents the electrochemical impedance behavior over a wide range of frequencies was designed. The associated impedances with the bulk electrolyte, Faradaic electrode processes and different pore size ranges were investigated using a truncated version of the standard transmission line model. The analysis considers the requirements of porous materials as electrodes in supercapacitor applications, reasons for their non-ideal performance and the concept of ‘best capacitance’ behavior in different frequency ranges. [ABSTRACT FROM AUTHOR]

Anisotropic, biomorphic (wood-derived) potassium-based geopolymer (KGP) - biocarbon (C B ) composites with net shape were manufactured by infiltrating KGP slurry into monolithic porous biocarbon (C B ) structures (~77 vol% porosity) derived from pyrolyzing beech wood. About 70% of the pores in the three-dimensional (3D) C B structures were infiltrated by the KGP slurry. Compared to pure KGP, the energy absorption per unit volume in compression loading of the KGP-C B composites was increased by ten-fold. After heat treatment at 1000 °C for 1 h in N 2 , the compressive strength of the KGP-C B composites increased from ~7–24 MPa, accompanied by the formation of crystalline leucite (K 2 O·Al 2 O 3 ·4SiO 2 ) phase in the KGP. The KGP-C B composite also exhibited three orders higher electrical conductivity than pure KGP. The effect of temperature on the formation of crystalline phases in KGP and KGP-C B composites was investigated. FTIR, TGA and SEM analyses were used to investigate the changes in microstructures and phase formation during thermal treatment. [ABSTRACT FROM AUTHOR]

Implementing metal-free electrocatalysts for the oxygen reduction reaction (ORR) and revealing crucial chemical or topographical parameters driving their activity are vital for the development of power cells. The carbon-based catalysts are very often synthesized through carbonization of biopolymers, in particular, those one containing nitrogen groups such as chitosan. Unfortunately, the resulting carbonaceous materials usually lack specific porosity and exhibit low catalytic activity. Here, we demonstrate that pyrolysis of chitosan in a ZnCl 2 melt assisted by the presence of LiCl results not only in a highly porous activated carbon material with a specific surface area of 1317.97 m 2 /g and the total nitrogen content of 6.5%, but also induces unexpected curvature in the grown graphitic layers. This is the first work that shows curved graphene layers obtained from a biopolymer precursor by its pyrolytic decomposition in the melted salt media. On the other hand, a carbonaceous material obtained from chitosan but without the salts has very low specific surface area of 7.8 m 2 /g, possesses no specific structural features, and contains 4.7% of nitrogen. The electrochemical studies show, that the former material is highly active towards four-electron pathway of the ORR in terms of an onset potential (0.89 V vs RHE) and the turnover frequency (TOF max  = 0.095 e site −1  s −1 ). We attribute this high catalytic performance to the presence of the pyridinic and pyrrolic sites in the structure. The ORR kinetics is probably further promoted by curvature in the graphitic layers. [ABSTRACT FROM AUTHOR]

Developing the low-cost, highly active carbonaceous materials for oxygen reduction reaction (ORR) catalysts has been a high-priority research direction for durable fuel cells. In this paper, two novel N-doped carbonaceous materials with flaky and rod-like morphology using the natural halloysite as template are obtained from urea nitrogen source as well as glucose (denoted as GU) and furfural (denoted as FU) carbon precursors, respectively, which can be directly applied as metal-free electrocatalysts for ORR in alkaline electrolyte. Importantly, compared with a benchmark Pt/C (20wt%) catalyst, the as-prepared carbon catalysts demonstrate higher retention in diffusion limiting current density (after 3000 cycles) and enhanced methanol tolerances with only 50-60mV negative shift in half-wave potentials. In addition, electrocatalytic activity, durability and methanol tolerant capability of the two N-doped carbon catalysts are systematically evaluated, and the underneath reasons of the outperformance of rod-like catalysts over the flaky are revealed. At last, the produced carbonaceous catalysts are also used as cathodes in the single cell H 2 /O 2 anion exchange membrane fuel cell (AEMFC), in which the rod-like FU delivers a peak power density as high as 703 mW cm −2 ( vs. 1106 mW cm −2 with a Pt/C benchmark cathode catalyst). [ABSTRACT FROM AUTHOR]

[Display omitted] • Battery-grade graphite was fabricated in 13 min at a low temperature of 1100 °C. • Fast carbonation is achieved by a multi-physics field carbonization coupling with a Ni catalyst. • Molecular dynamics revealed the exceptional kinetics carbonization by MPF. • The obtained graphite anode provides a reversible Li+ storage capacity of 370.7 mAh g−1. • The graphite anode delivers long cycling life over 10,000 cycles at 2 A g−1 in diglyme-based Na-ion batteries. The typical synthesis of graphite requires carbonization at 2800 °C, which consumes a substantial amount of energy. We present a novel, sustainable and cost-effective method for synthesizing high-crystallinity graphite in 13 min at a low temperature of 1100 °C and a multi-physics field (MPF) carbonization coupling with a Ni catalyst. The MPF synergistically benefits from a thermal field, an electric field, and a pressure field in an MPF furnace at the lab scale. Molecular dynamics and differential charge density calculation indicated that the MPF carbonization facilitated exceptional kinetics, and considerably accelerated the breaking of the Ni-metal-catalyzed C-O bonds. The starch-derived graphite anode provided a reversible Li+ storage capacity of 370.7 mAh g−1, matching that of commercial graphite. It also demonstrates exceptional rate performance with a capacity of 103.3 mAh g−1 at an ultra-high current density of 30 A g−1 in diglyme-based Na-ion batteries and ultrastable cycling performance over 10,000 cycles at 2 A g−1. This method will shed some light on how to rapidly fabricate highly crystalline graphite by a energy-saving and low-cost route. [ABSTRACT FROM AUTHOR]

Sustainable and green manufacturing of hard carbon (HC) material in a low-cost way is the key issue in promoting its industrial applications in Na-ion batteries (SIB). Nowadays, most synthesis ways to prepare HC need the help of chemical reagents to improve its Na-ion storage performance. Herein, we firstly developed a completely green biological fermentation technology to prepare HCs on a large scale using cheap and renewable carbon sources of various biomass starch. Pre-treatment by bio-fermentation can effectively modify the carbon precursor for facile pyrolysis to fabricate starch-based HCs, and make its internal microstructure with larger interlayer spacing, more disordered structure and abundant closed micropores. Finally, a case of cornstarch-based hard carbon exhibits a high reversible capacity of 335 mA h g−1 at a current density of 30 mA h g−1 and high rate performance with a reversible capacity of 140.6 mA h g−1 even at a high current of 5 A g−1 as well as long cycling stability. In-situ Raman spectra, ex-situ SAXS and ex-situ XPS tests during discharge and charge process reveal the pore filling mechanism of quasi-metallic Na in hard carbon anode. Such a "bread-making"strategy is a facile and scalable route to fabricate various starch-based hard carbons with improved performance, demonstrating a very practically promising application for industrial manufacture. • A green biological fermentation technology to prepare HCs is firstly developed. • Renewable carbon sources of various biomass starch derived HCs are achieved. • Bio-fermentation effectively improve interlayer spacing with abundant closed micropores. • HC with a reversible capacity of 335 mA h g−1 and long cycling stability is demonstrated. • Such a "bread-making" strategy is a scalable route to fabricate hard carbons at a kilogram. [ABSTRACT FROM AUTHOR]

Chitosan, glucosamine, a glucose-melamine mixture, a glucose polyvinylpyrrolidone mixture, and a glucose poly(vinylpyrrolidone- co -vinylimidazole) mixture are examined in a hydrothermal carbonization and calcining process to investigate effects of nitrogen additives on incorporation of nitrogen into the carbon products and the effects of such additives on morphology and porosity. The resulting calcined hydrothermal carbons are examined for their aqueous dispersibility using a nanolatex (NL) stabilizer based on an ionic liquid imidazolium acrylate monomer. Sonication of water, nanolatex, and carbon mixtures shows that ease of dispersion and friability increase with carbon porosity. This is the first report connecting friability with porosity on μm to nm length scales. Scanning electron microscopy of carbon dispersions in excess NL suggests adsorption of NL from suspension is random and irreversible, and accompanied by conformational equilibration and spreading. Thin films made from aqueous dispersions and from sediments obtained by centrifugation of such dispersions exhibit electrical and thermal conductivities that can be understood in terms of how the carbon particles pack in a gravitational or centrifugal field. The most porous carbon is found to produce an optical extinction in the visible on the order of that exhibited by single wall carbon nanotubes. Carbon produced hydrothermally from glucose and melamine appears to be a layered material that is electrically insulating while appreciably thermally conducting. [ABSTRACT FROM AUTHOR]

A simple, cost-effective and scalable approach for the synthesis of N-doped mesoporous carbons that are effective as ORR catalysts is reported. The synthesis procedure involves two steps: a) production of mesoporous carbons using a template-free approach based on the carbonization of citrate salts of zinc and calcium, and b) N-doping by heat treatment in the presence of melamine. The resulting N-doped carbon possess a high specific surface area, a porosity made up exclusively of mesopores and a large amount of nitrogen functionalities (∼8–9 wt%). When used as an electrocatalyst for the oxygen reduction reaction (ORR), the metal-free carbon materials predominantly catalyze the 4 e − process, with an onset potential of 0.9 V ( vs. RHE) and a superior kinetic current density (∼17 mA cm −2 ) to that of Pt/C at ∼0.6 V under basic conditions. In addition, the developed catalysts show a higher stability than commercial Pt/C and excellent electrocatalytic selectivity against methanol crossover. [ABSTRACT FROM AUTHOR]

To resolve an increasing global demand in energy, a source of sustainable and environmentally friendly energy is needed. Microbial fuel cells (MFC) hold great potential as a sustainable and green bioenergy conversion technology that uses waste as the feedstock. This work pursues the development of an effective small-scale MFC for energy generation from urine. An innovative air-cathode miniature MFC was developed, and the effect of electrode length was investigated. Two different biomass derived catalysts were also studied. Doubling the electrode length resulted in the power density increasing by one order of magnitude (from 0.053 to 0.580 W m −3 ). When three devices were electrically connected in parallel, the power output was over 10 times higher compared to individual units. The use of biomass-derived oxygen reduction reaction catalysts at the cathode increased the power density generated by the MFC up to 1.95 W m −3 , thus demonstrating the value of sustainable catalysts for cathodic reactions in MFCs. [ABSTRACT FROM AUTHOR]

Herein we presented, for the first time, facile fabrication of nitrogen doped (0.5–4 wt.%) porous carbon aerogels using biomass derivatives ( i.e. glucose or cellulose) as the carbon precursor and soy protein as both the nitrogen precursor and the structure directing agent. Through post thermal treatment to improve the electrical conductivity and porosity, the obtained materials showed excellent oxygen reduction reaction (ORR) catalytic activity. The electrochemical performance was further enhanced after platinum impregnation, combining the advantages of small over-potential from platinum catalyst and high limiting current density from the carbon substrate. Therefore, we demonstrated here not only a novel and low cost hydrothermal synthesis route to achieve high-performing metal-free ORR catalyst or carbon substrate for additional metal catalyst, but also a general principle on how to develop metal nanoparticles/carbon hybrids for ORR. [ABSTRACT FROM AUTHOR]

Abstract: Photodegradation of methylene blue on a carbon-doped TiO2 and on pure TiO2 was studied. The materials were prepared by solvothermal synthesis and by calcinations. N2 adsorption, XRD, SEM and TEM characterization was performed. Both nanomaterials exhibited mesoporous textures and the TiO2 frameworks consist mainly of anatase phase. SEM images showed spherical microparticles while the TEM images showed hierarchically nanostructured morphologies on both samples. C-TiO2 exhibited higher apparent first-order rate constants for the degradation of methylene blue than those obtained on pure TiO2. It could be concluded that under visible light, the photoactivity of carbon-doped TiO2 was clearly higher than that of a commercial TiO2 photocatalyst suggesting that the carbon part photo assist the TiO2 in the photodegradation of methylene blue. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen-doped carbons were produced using hydrothermal carbonization of nitrogen-containing carbohydrates under mild temperature (180°C). The resulting materials contain significant amounts of nitrogen and display a high degree of aromatization. The nitrogen contents are also retained after further calcination at higher temperatures. All the resulting materials have been thoroughly characterized using X-ray photoelectron spectroscopy, solid state 15N and 13C-nuclear magnetic resonance, elemental chemical analysis, nitrogen adsorption, scanning and transmission electron microscopy. The nitrogen-doped materials proved to have superior performance with respect to their nitrogen-free counterparts in terms of electrical conductivity. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen-doped carbon particles were produced using the hydrothermal carbonization of a nitrogen-containing carbohydrate, namely glucosamine, under mild temperature conditions (180 °C) followed by further calcination under a stream of inert gas at 750 °C. The resulting materials contain significant amounts of nitrogen doping within their structure, mainly as quaternary N involved in an aromatized/graphitized carbon structure according to X-ray photoelectron spectroscopy. This nitrogen-doped material was dispersed with nanolatexes having a high affinity for carbon. The resulting hybrid dispersions could be conveniently cast into dense and stable films for thermal and electrical conductivity measurements. The conductivities were commensurate with technical carbon nanotube latex-based films. A morphological analysis of the dispersing mechanism suggests that the potential for high performance materials realized in this contribution is very competitive, but still far from being fully exploited. [Copyright &y& Elsevier]

Abstract: Greenhouse gas mitigation options include the production of carbonized materials and their addition to soils for longer term storage. Hydrothermal carbonization (HTC) is a novel way to produce carbonized materials. The goal here was to test if HTC material, in our case derived from beet root chips, has adverse effects on plant growth or that of root associated symbionts such as arbuscular mycorrhizal fungi. We carried out several studies, and found that increasing concentrations of HTC material could be deleterious for plant growth of Taraxacum, starting at 10vol% additions. Conversely, root colonization of the fungal symbiont was stimulated at an addition of 20vol%. Soil pH changes occurring during the study could be traced to microbial reduction reactions, and these led to a pH increase of the medium despite the quite acidic nature of the HTC material itself. In separate assays, we showed that spore germination of the AM fungus Glomus intraradices was stimulated by the HTC material, suggesting that direct effects on the fungi are likely in addition to those mediated by the host plant. A third experiment with a different plant species (Trifolium repens) confirmed the major conclusions, and showed also neutral to stimulatory effect on nodulation. Our results suggest that HTC materials should be carefully tested and optimized to reduce negative effects on plant growth before applications in the field are undertaken, particularly at high addition rates. [Copyright &y& Elsevier]

Abstract: We describe the production and catalytic application of highly functionalized mesoporous carbonaceous materials, obtained via a one step green and cheap process relying on the hydrothermal carbonization of carbohydrates (e.g. glucose) in the presence of functional organic monomers (e.g. vinyl imidazole). The resulting materials could be further functionalized to feature imidazolium bromides on their surface and be used for various transesterification, Knoevenagel and Aldol reactions. [Copyright &y& Elsevier]

Abstract: A comprehensive comparison of five chromatographic stationary phases based on molecularly imprinted polymers is presented. Efficiency, imprinting factors, water compatibility and batch-to-batch reproducibility are discussed for crushed monolith, microspheres, two silica-based composites and capillary monoliths, all imprinted with the local anaesthetic bupivacaine. Synthesis protocol and chromatographic test conditions have been kept fixed within certain limits, in order to provide further insight into the strengths and weaknesses of the different formats. Excluding microparticles, all formats give satisfactory performance, especially in aqueous mobile phases. An assessment of batch-to-batch reproducibility in different mobile phases adds further value to this comparison study. [Copyright &y& Elsevier]

Photoelectrochemical imaging has great potential in the label-free investigation of cellular processes. Herein, we report a new fast photoelectrochemical imaging system (PEIS) for DC photocurrent imaging of live cells, which combines high speed with excellent lateral resolution and high photocurrent stability, which are all crucial for studying dynamic cellular processes. An analog micromirror was adopted to raster the sensor substrate, enabling high-speed imaging. α-Fe 2 O 3 (hematite) thin films synthesized via electrodeposition were used as a robust substrate with high photocurrent and good spatial resolution. The capabilities of this system were demonstrated by monitoring cell responses to permeabilization with Triton X-100. The ability to carry out dynamic functional imaging of multiple cells simultaneously provides improved confidence in the data than could be achieved with the slower electrochemical single-cell imaging techniques described previously. When monitoring pH changes, the PEIS can achieve frame rates of 8 frames per second. [Display omitted] • Photoelectrochemical imaging setup with high spatiotemporal resolution developed. • Fast, high-resolution pH imaging at a rate of 8 frames per second. • Real-time live-cell imaging of permeabilization of cell membranes with surfactant. • Biocompatible and stable hematite substrate as sensor chip for live cell imaging. [ABSTRACT FROM AUTHOR]

We successfully construct noble-metal-free cobalt nitride/nitrogen-rich carbons (Co 4 N/NCs) catalysts by a photochemical assembly strategy. The obtained Co 4 N/NCs catalysts show extraordinary activity for CO 2 -to-CO reduction. The highest turnover frequency per cobalt atom within Co 4 N/NCs reaches 6.7 s-1. • Cobalt nitride/nitrogen-rich carbons (Co 4 N/NCs) are prepared by a photochemical approach. • The Co 4 N/NCs is an effective catalyst for CO 2 reduction. • The quantum yield for CO production over the Co 4 N/NCs reaches 7.2% at 450 nm. Utilizing solar energy to convert CO 2 into fuels and chemicals represents a promising solution to reduce reliance on fossil fuels, but it is hampered by the lack of highly-efficient catalysts. Herein, we report unique cobalt nitride/nitrogen-rich carbons (Co 4 N/NCs), which can work as noble-metal-free catalysts for CO 2 -to-CO conversion. The mass activity of Co 4 N/NCs is two orders of magnitude higher than those of previously reported CO 2 photoreduction catalysts. The quantum yield for CO production at 450 nm reaches 7.2% with a turnover frequency per Co atom of 0.97 s-1. The electronic structure and coordinated environment of catalysts are analyzed by X-ray absorption fine structure spectroscopy and X-ray photoelectron spectroscopy. The reaction processes are investigated by in-situ diffuse reflectance infrared fourier transform spectroscopy and density functional theory calculations. Results suggest that the synergetic effects between the Co 4 N and the NCs can consolidate the adsorption and activation of CO 2 and accelerate the interfacial electron-transfer kinetics between the Co 4 N/NCs catalysts and light-harvesting antenna, thereby resulting in the outstanding activity for synthesizing CO from CO 2. This work offers the possibility to design Co-based host-guest topology for highly-efficient CO 2 reduction. [ABSTRACT FROM AUTHOR]

Brewer's spent grains (BSG) represent a highly abundant byproduct generated in the beer industry. Owing to abundant availability and high water content, BSG constitutes a raw material of interest for thermochemical conversion via hydrothermal carbonization (HTC). Nevertheless, the phyto-toxic effect and low-porosity of hydrochars limit the possible application. Therefore, coupling HTC and pyrolysis may overcome these obstacles. HTC experiments were carried out at 180, 220, and 260 °C and pyrolysis was performed at 400, 600, 800, and 1000 °C to investigate the influence of HTC on the pyrolysis of BSG. Pyrolyzed hydrochars showed lower ash content and higher carbon content compared to char obtained from BSG. The highest surface area (139.5 m2 g−1) was obtained for hydrochar produced at 180 °C and then pyrolyzed at 600 °C. This value was 70% higher compared to BSG pyrolyzed at the same temperature (82 m2 g−1). The coupling of HTC and pyrolysis showed synergies in the char yield, reduction of ash, increasing of carbon content, and porosity. The promising results proved that at selected process conditions, the novel route is beneficial for carbon materials production due to the improvement of the physicochemical properties of pyrochar at similar mass and carbon yields. Image 1 • One-step pyrolysis and two-step HTC coupled with pyrolysis was investigated. • Low-temperature HTC in two-step process resulted in similar char yield as pyrolysis. • Coupling of HTC and pyrolysis improved physicochemical properties of pyrochars. • Highest S BET was achieved for hydrochar obtained at 180 °C and pyrolyzed at 600 °C. [ABSTRACT FROM AUTHOR]

The nitrogen vacancies on the carbon nitride surface can function as active sites to catalyze water oxidation reaction, while preventing recombination of the electron/hole pairs, thus accelerating the reaction kinetic of oxygen photosynthesis. • A photocarving strategy is first employed to create nitrogen vacancies (NVs) on the surface of polymeric carbon nitride (PCN). • The embedded NVs can function as active sites to catalyze oxygen evolution reaction (OER), thereby accelerating the sluggish kinetic of OER. • The embedded NVs can effectively promote the separation and transfer of the photogenerated charge carrier. • The PCN-NVs without any extra metal cocatalyst assistance exhibits a 4.2-fold increase in the oxygen photosynthesis activity compared with pristine PCN. Photocatalytic water splitting necessitates robust cocatalysts to accelerate the oxygen evolution reaction (OER). However, most OER cocatalysts are based on noble metal oxides. Besides, the loose interface between semiconductor and cocatalyst results in inefficient charge transfer. The fabrication of photocatalysts with integrated light-harvesting and catalytic centers for OER is therefore desired. Herein, we provide a photocarving strategy to create nitrogen vacancies (NVs) on polymeric carbon nitride (PCN). It is confirmed that the embedded NVs can function as active sites to catalyze OER, while promoting the transfer of the photogenerated charge for OER. As a result, PCN-NVs without any extra noble-metal cocatalyst assistance exhibit an enhanced oxygen evolution rate compared with the pristine PCN. Additionally, the PCN obtained from other precursors can also be engineered by this photocarving method, while promoting oxygen photosynthesis. This work provides an avenue to design light-transducers with combined light-harvesting and catalytic configurations for oxygen synthesis chemistry. [ABSTRACT FROM AUTHOR]

Pyrolysis provides an attractive alternative for the upgrading of agro-wastes to energy and chemicals. However, consistent quality of the final products is still a goal to be achieved at industrial level. The present study aims at complementing existing results recently published by the authors and investigating the physico-chemical evolution and oxidative reactivity of solid products of pyrolysis of citrus waste. Chars derived from slow pyrolysis (50 °C min−1, 200–650 °C peak temperature) of orange and lemon pulp (OP and LP) in a horizontal batch reactor were characterized by means of Thermo-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Electron Paramagnetic Resonance (EPR) and Raman spectroscopy. Results show how the onset of breaking of covalent bonds in matrix is triggered by reaching pyrolysis temperatures of 330–350 °C. Around those temperatures, the population of free-radicals significantly increases on solids and chars become more reactive, thereby favoring retrogressive, recombination and secondary solid-vapor reactions. Results also show that the higher content of lignin on LP may facilitate the formation of aromatic networks via lignin fragmentation and condensation above 500 °C. This trend is also confirmed by DSC patterns in which, above 500 °C, significantly more endothermic reactions occur in LP as a comparison to OP. This conclusion is further corroborated by more pronounced G-band Raman shifts shown for LP as a comparison to OP. The present results shed new light on the thermochemical breakdown of solid agro-wastes and provide insights for development of slow pyrolysis technology toward the production of valuable renewable carbonaceous materials. [ABSTRACT FROM AUTHOR]