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Carbon fiber paper (CFP) is one of the most widely used gas diffusion layer materials for proton exchange membrane fuel cells (PEMFC) due to its excellent properties such as high conductivity, high strength, high air permeability and corrosion resistance. In this study, CFP was prepared using the phenolic resin (PF) in-pulp addition method. The effect of PF content on the properties of hot-pressed paper (HPP) and CFP was investigated. The results showed that when the dosage of polyethylene oxide (PEO) was 1.5 wt%, the flocculation effect of PEO on PF was basically complete, and the water filterability and retention of carbon fiber pulp were relatively optimal. After HPP was carbonized into CFP, the hydrophobicity, average pore size, porosity, and air permeability increased, while the resistivity and tensile strength decreased. With the increase of PF content, the tensile strength of CFP gradually increased, while the average pore size, porosity, air permeability and resistivity decreased. When the PF content was 250 wt%, the average pore size of CFP was 36.5 μm, the water contact angle was 127°, the porosity was 69.7%, the air permeability was 7.81 × 103 mL mm/(cm2·h·mmHg), the resistivity was 21.1 mΩ cm, and the tensile strength was 15.7 MPa. In addition, the CFP prepared using PF in-pulp addition method had a relativity uniform pore size distribution and high air permeability. Therefore, this work shows that the CFP prepared using this technique exhibits excellent comprehensive performance, and enables the manufacturing of CFP to be more efficient, low-cost, and environmentally friendly. [Display omitted] • Carbon fiber paper was prepared efficiently using the phenolic resin in-pulp addition method. • Polyethylene oxide exhibits strong adsorption ability on phenolic resin in carbon fiber pulp. • The melting temperature of phenolic resin is a critical point in the preparation process of carbon fiber paper. • Carbon fiber paper possesses a relatively uniform pore size distribution and high air permeability. [ABSTRACT FROM AUTHOR]

Development of low-cost, efficient, and stable oxygen evolution electrocatalysts is crucial for the conversion and storage of renewable energy. Therefore, an effective integrated heterostructure catalyst is needed to achieve a lower overpotential during oxygen evolution process. In this paper, cobalt-zinc bimetallic MOF precursors are used as templates to prepare bimetallic cobalt-based selenides with good oxygen evolution catalytic activity and stability on carbon fiber paper. Due to the high specific surface area and porous structure of the coupling structure of nanorods and polyhedra, and the strong electronic coupling between CoSe 2 and ZnSe on nanorods. CoSe 2 -ZnSe/CP exhibits excellent electrocatalytic activity in 1 M KOH solution. It only requires an overpotential of 275 mV to reach the current density of 10 mA cm-2, and the Tafel slope is 68.9 mV dec-1. In addition, after 12 h of continuous operation of CoSe 2 -ZnSe/CP, the activity decay of the catalyst is negligible. This work provides a method for the design of heterogeneous bimetallic selenide integrated oxygen evolution electrocatalysts. [Display omitted] • The CoSe 2 -ZnSe/CP catalyst is obtained by selenization of MOF precursor at high temperature. • The catalyst has unique nanorod-coupled polyhedral morphology and high specific surface area. • The strong electron coupling between CoSe 2 and ZnSe improves the oxygen evolution activity. • CoSe 2 -ZnSe/CP exhibits low overpotential, high exchange current density and fast kinetics. [ABSTRACT FROM AUTHOR]

Carbon paper as a macroporous substrate of gas diffusion layer in proton exchange membrane fuel cells directly impacts the output performance of cells. In this study, we present a straightforward strategy to improve the overall performance of carbon paper by mixing short/long (6mm/10 mm) chopped carbon fibers at an optimal concentration of phenolic resin. The results show that incorporating longer carbon fibers can increase the porosity, conductivity, gas flux, and mechanical properties of carbon paper. The membrane electrode assembly achieved a peak power density of 1182.61 mW cm−2 at 60% RH using carbon paper with a long carbon fiber content of 40 wt% and an impregnation concentration of 10 wt%. This outperforms commercially available carbon paper. Based on electrochemical impedance spectroscopy results, it was confirmed that our carbon paper had a lower mass transfer resistance of only 32.17 mΩ cm−2 under conditions of 2 A cm−2 and 60% RH. This was due to its sparser three−dimensional network-like pore structure which was created by mixing different lengths (6mm/10 mm) of carbon fibers. This work provides new insights into preparing high−performance carbon papers. • The nature of carbon paper is regulated by mixing short/long (6mm/10 mm) CFs ratio. • The long carbon fiber contents of 20–40 wt% present better physical properties. • The optimal carbon papers can mitigate mass transfer resistance. • MEA composed of the optimal CP shows a higher power density than commercial CP. [ABSTRACT FROM AUTHOR]

A facile method is proposed in this work to prepare a carbon paper (CP) with outstanding properties by doping boron to catalyze graphitization at lower temperature. Boron was introduced into CP by impregnating carbon fiber preform into a boron/phenolic resin/ethanol solution, and then CP was obtained after the consecutive procedures of hot pressing, carbonization, and graphitization. Morphology, microstructure, composition, and physical properties of the doped and undoped CPs were thoroughly investigated via various techniques to exam the effects of boron concentration and graphitization temperature. Furthermore, the boron doped CP was fabricated into fuel cell gas diffusion layer (GDL) and membrane electrode assembly (MEA) to evaluate its performance through the single cell performance. The findings indicated CP doping with 2 wt% boron could lower the graphitization temperature by at least 200 °C. The B-doped GDL had a higher power density in comparison with the undoped GDLs made in our lab or from the commercial brands. • The innovative preparation method for carbon paper with high conductivity. • The effect of boron concentration and graphitization temperature on carbon paper. • The single cell performance of B-doped gas diffusion layer. [ABSTRACT FROM AUTHOR]

The solar photocatalytic degradation of pulp and paper mill wastewater has been reported by several scientists. However, this is the first time we are reporting for solar photocatalytic hydrogen production from pulp and paper mill wastewater and simultaneous degradation of pollutants. In this work, CuO based photocatalysts and novel square type photocatalytic reactor of 5 L capacity were used. The result shows that the prepared photocatalysts are solar active, efficient in hydrogen recovery and pollutant degradation from the pulp and paper wastewater. The effects of catalyst loading, sacrificial agent, pollutant removal efficiency and stability check were investigated. At 0.25 g/L of CuO/Fe 2 O 3 , 0.2 M of sacrificial agent (Na 2 SO 3 2−) and hydrogen yield of 1000 mL from 1000 mL of wastewater was achieved. The removal efficiency of TSS, TDS, BOD, COD, turbidity and TOC are around 70, 50, 60, 65, 70 and 45% respectively. Reusability study revealed that CuO/Fe 2 O 3 was chemically stable and could be reused successively (five cycles) without significant changes in its photoactivity and intrinsic properties. [Display omitted] • Visible light active CuO mixed with novel metal oxides were employed. • Hydrogen recovery from black liquor, paper mill wastewater were 1000 mL/h/L and 850 mL/h/L. • Efficiency of degradation of pulp & paper wastewater chemicals were around 50–70%. • AcHieved high recovery of hydrogen from pulp & paper wastewater. [ABSTRACT FROM AUTHOR]

The Proton Exchange Membrane Fuel Cell (PEMFC) performances are strongly impacted by the compression of the Gas Diffusion Layer (GDL). Despite its fibrous microstructure, this material is usually considered as a continuous medium and characterized with uniform loading. However, the GDL is subjected to a heterogeneous compression onto rib/channel patterns in the fuel cell assembly. In the present study, a complex behavior of the GDL response is experimentally revealed when the material is loaded with a rib/channel pattern, compared to uniform compression. The tests are simulated by finite element modeling using a classical strain-dependent elastic law, using parameters fitted from uniform compression experiments. It is shown that the numerical results do not reproduce the effect of pattern observed experimentally. Hypotheses to interpret these results involve mechanisms at the fiber microscale including fiber fracture, cross-link breakage and fiber rearrangement, which are exacerbated by larger material deformation caused by the heterogeneous loading. • Unexpected impact of rib/channel patterns on GDL compression. • Experimental investigation of the effect of rib/channel width on GDL deformation. • Numerical study with classical model unable to reproduce experimental results. • Interpretations based on mechanisms at the fiber microscale. [ABSTRACT FROM AUTHOR]

A noble-metal-free bifunctional electrocatalyst with outstanding activity and stability is of great importance for the development of rechargeable zinc-air batteries (ZABs). Herein, we employed a facile strategy to fabricate nitrogen-doped NiCo 2 O 4 nanostructures on carbon paper as a binder-free air cathode for rechargeable ZABs. An optimized process of nitrogen plasma treatment has enhanced the electrical conductivity of the metal oxide and induced abundant active sites into the crystal structures, resulting in enhanced electrocatalytic activities toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Notably, mild plasma treatment leads to efficient N doping while the morphology and specific surface area of the catalyst both remain unchanged. The air cathode with NiCo 2 O 4 doped with nitrogen in 2 min plasma treatment and integrated into a zinc-air battery with liquid electrolyte provided a small charge-discharge voltage gap and distinguished cycling stability superior to the air cathode with noble-metal catalyst counterparts. Furthermore, the solid-state zinc-air battery with this material displays excellent stability with just a small increase of the charge-discharge voltage gap over 20 h of operation. This work illustrates the promising potential of plasma treatment in the fabrication of high-performance catalysts. • N-doped NiCo 2 O 4 was prepared by hydrothermal method and N 2 plasma treatment. • Mild plasma treatment leads to efficient N doping in NiCo 2 O 4. • NiCo 2 O 4 with N 2 plasma treatment of 2 min exhibits excellent OER/ORR performances. • N–NiCo 2 O 4 -2 min worked as a binder-free air cathode in Zn-air batteries. [ABSTRACT FROM AUTHOR]

The large-scale development of flexible electrode is urgently needed for water electrosplitting. Herein, the common and low-cost filter paper (FP) is utilized as the substrate to adjust the flexible property of the catalytic electrode. Through an electroless plating method, the NiFeP alloys were deposited onto the filter paper, which acted as the flexible and self-supported electrode for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The resultant NiFeP@FPs require low overpotentials of 158 mV for HER and 282 mV for OER to deliver a current density of 10 mA cm−2, and exhibit a good stability of 30 h in 1 M KOH. The synergistic effect of Fe–Ni sites regulates electron structure and boosts the catalytic activity. Benefited from good hydrophilicity and interlaced fiber structure of filter paper, electrolyte penetration and electron transfer in the sample are promoted. The assembled two-electrode electrolyzer only requires 1.814 V to achieve 100 mA cm−2 for overall water splitting and shows excellent stability. This work provides a new strategy for the development of flexible and efficient electrodes for water splitting, which advances the development of wearable electronic devices. [Display omitted] • The flexible filter paper-based electrode was successfully synthesized. • The good hydrophilicity and porous structure facilitated electrolyte permeation. • The sample required low overpotentials of 158 mV for HER and 282 mV for OER. • The two-electrode electrolyzer provided 100 mA cm−2 at a low voltage of 1.814 V. [ABSTRACT FROM AUTHOR]

Black liquor (BL) bioconversion into valuable by-products is essential to develop a bioeconomy strategy; however, its furfural content hinders microbial fermentation activities. Hence, this study utilizes paper mill sludge (PMS) to provide extracellular enzymes, furfural-degrading microbial consortia, and electron donor required for promoting the BL hydrogenesis potential. Three up-flow anaerobic sequential batch reactors (UASBRs) are fed with PMS (UASBR1), BL (UASBR2), and PMS + BL (UASBR3) and operated in parallel at 15 min fill, 72 h reaction, and 4 h settling. The UASBR3 achieves the maximum volumetric H 2 of 1.483 ± 0.088 L/L/d and H 2 yield of 2.06 ± 0.12 mol/mol glucose, which drops by 88% in UASBR2 and 24% in UASBR1. The insufficient H 2 productivity values in UASBR2 could be due to a lack of nutrients availability (C:N = 440:1 and C:P = 19:1), higher furfural concentration (2116 ± 422 mg/L), and involvement of the butyrate fermentation pathway. The synergetic effect between PMS and BL overcomes these limitations and enriches the fermentation medium with Proteobacteria phyla (22.8%) and Acinetobacter sp. degrading furfural (6.1%). The microbial community at the phylum level (e.g., Proteobacteria , Firmicutes , and Actinobacteria) in UASBR3 maximizes the migration of electrons (e−eq = 9.34 ± 0.54%) towards efficient H 2 formation. [Display omitted] • Paper mill sludge (PMS) mitigated inhibitory effect of furfural in black liquor (BL). • PMS improved H 2 yield from the BL by 8.3-folds and accounted for 2.1 mol/mol glucose. • e– eq transferred to H 2 was 9.3% in the PMS:BL, 7.4% in PMS, and 1.27% in BL. • Acinetobacter degrading furfural (6.1%) was abundant with PMS addition. • Bacilli (8.9%) and Clostridia (5.4%) was dominant in the hydrogenesis of PMS:BL. [ABSTRACT FROM AUTHOR]

This research investigated the hydrogen production and energy conversion from automobile shredder residues (ASRs) and paper mill sludge (PMS) co-gasified in a full-scale fluidized bed gasification plant. The results obtained from full-scale tests provided important information on the feasible assessment of ASRs-to-energy and the selection of alternative technologies for ASRs. Based on the analysis results of produced gas composition, H 2 , CO, and CH 4 composition produced from paper-mill sludge gasified were 4.17%–6.01%, 3.08%–4.32%, 1.71%–2.4%, respectively. Another C 2 gas composition ranged from 2.9% to 3.59%. The heating value of produced gas ranged between 1.64 MJ/Nm3 and 2.18 MJ/Nm3. In the case of 10% ASR addition, the heating value of produced gas was slightly increased to 1.84 MJ/Nm3-2.34 MJ/Nm3. The dioxin emission concentration of flue gas was approximately 0.064 ng I-TEQ/Nm3. It can comply with Taiwan regulation thresholds. The dioxin leaching concentrations of residues derived from gasification were also in compliance with regulation limits by the TCLP test. Meanwhile, in the case of 10% ASRs addition, the dioxin equivalence concentration of gasified residue was nearly 0.002 ng I-TEQ/Nm3. It was far below the current regulation standard limit. In summary, the results of this research have proved the performance of ASRs-to-energy by co-gasified with paper mill sludge using a full-scale gasification plant. The results obtained from this research also provided the information for selecting ASRs alternative technologies and operating full-scale gasifiers in the future. [Display omitted] • This study has confirmed the feasibility of co-gasification of calcium-rich PMS and chlorine-rich ASRs. • Adding 5%–15% of ASRs can maintain the regular operation of the full-scale commercial gasifier. • The synthesis gas has a composition of 4.91 vol% H 2 and 2.06 vol% CO, with a LHV of 1.93 MJ/Nm3. • The HCl emission could comply with regulation thresholds in co-gasification. • Dioxin reformation reduced significantly in co-gasification of PMS and ASRs. [ABSTRACT FROM AUTHOR]

In this study, practical application for the industrial-scale hydrogen evolution reaction (HER) process is established using sustainable Cu 2 CoSnS 4 embedded in paper-working electrodes. The Cu 2 CoSnS 4 is produced using a solvent-free solid-phase approach. The effect of a wide pH range of electrolytes on working electrodes for hydrogen evolution reactions is also investigated. The Cu 2 CoSnS 4 embedded paper-working electrodes exhibit goodelectrocatalytic activity for hydrogen evolution reaction with low overpotential values of 233, 310, and 261 mV vs RHE at 10 mA/cm 2 in 0.5 M H 2 SO 4 ,1 M KOH, and 1 M PBS, respectively. These designed electrodes exhibit high double-layer capacitance and electrochemical surface area for a wide pH range. In acidic, alkaline and neutral environments, the catalyst-embedded paper electrodes explicit high turnover frequencies of 2.15 s−1, 2.75 s−1, and 2.11 s−1, respectively. The temperature-dependent hydrogen evolution reaction is studied to calculate the activation energy of the cathodic electrode. Utilising chrono-amperometry for about 118 h in an acidic media, which shows that electrodes have a high degree of stability. In comparison to other previously reported work on catalyst-embedded electrodes, the Cu 2 CoSnS 4 embedded paper-working electrodes offer excellentpotential for HER activity across a wide pH range and are suitable for industrial application. • Cu 2 CoSnS 4 embedded paper working electrodes are developed for hydrogen generation. • The electrodes exhibit universal pH hydrogen evolution reaction. • Electrodes shows excellent stability upto 40hr for continuous hydrogen generation. • The electrode displays good stability at current density more than 200 mA/cm2. [ABSTRACT FROM AUTHOR]

Paper-type gas diffusion layer (GDL) plays the role of structural support, mass transport, electron and heat transfer in the fuel cell. The deformation and fracture behavior of paper-type GDL directly determines its physical characteristics. In this paper, we obtained the distribution function of fiber length among intersections using statistical analysis. Based on the bending theory and fracture analysis, the deformation model and the maximum allowable pressure criterion of paper-type GDL are established. The deformation modulus is related to the modulus and the initial volume fraction of carbon fiber, with an ideal value of 1.4 MPa. The tensile fracture is the main form of fiber fracture. The maximum allowable pressure is related to the expected fracture probability, the strength and the initial volume fraction of carbon fiber. The residual strain increases and the deformation modulus decreases with load range, which means that the strength of the paper-type GDL is weakened when residual strain occurs. [Display omitted] • The fiber length between intersections obeys exponential distribution function. • The compression deformation model of paper-type GDL is established. • The maximum allowable pressure criterion for the paper-type GDL is obtained. [ABSTRACT FROM AUTHOR]

A thermal method of synthesis and fixation of Pt nanoparticles (Pt NPs) on carbon paper is proposed in this paper. Carbon paper was coated with H 2 PtCl 6 by simple immersion in an ethanol solution containing the Pt precursor. Thereafter, H 2 PtCl 6 was decomposed in inert atmosphere into Pt NPs by applying a temperature of 600 °C. Formed Pt NPs were able to oxidize the surrounding carbon fiber surface. This local thermal oxidation of carbon promoted the generation of nano-roughness and Pt NPs were embedded in the carbon fiber, thus favoring their fixation on carbon paper. Pt load can be easily controlled by the number of coating processes applied. The proposed method combines the advantage of achieving small size nanoparticles (5–10 nm) with enhanced fixation of Pt NPs when compared with electrochemical synthesis. The optimal number of coatings applied was three, which produced a complete coverage of carbon paper surface (with a Pt load of 0.18 mg cm−2). • Thermal method of synthesis of PtNPs on carbon paper. • Formed PtNPs locally oxidize carbon paper support. • Pt nanoparticles are embedded in carbon paper fibers. • Size of Pt nanoparticles obtained is around 5–10 nm. • Thermal synthesis of PtNPs produce more electroactive NPs than electrochemical one. [ABSTRACT FROM AUTHOR]

Micro Fuel cells or microfluidic fuel cells (μMFCs) are one of the most promising power supplies for portable electronics. However, the necessary electrode spacing is required to prevent fuel-crossover and maintain the stable operation, introducing the unavoidable ohmic resistance and retarding the miniaturization. Herein, we propose a novel μMFC device combining the cellulose paper as separator, with selective catalysts at the cathode side to eliminate the unwanted side reactions and increase the system compactness. One single reactant solution containing fuel and electrolyte is applied to keep the device stable operation. The power-generation properties are evaluated in typical alkaline conditions. A great construction simplification makes the device a substantial high-power density of 2.14 W cm−3 and maximum current density of 15.82 A cm−3. The μMFC stacks are arranged in series and parallel manners, which delivers a maximum power output of 23.6 mW and current of 194.6 mA. It is expected that innovative and customizable performance from commercial paper and low-cost carbonaceous catalysts can provide a forum for future advancement in chip-based electrochemical energy generation and storage devices. • Filter paper served as a membrane for μMFC is proposed. • The electrode-pair distance is greatly minimized (∼140 μm). • The optimized μMFC delivers an ultrahigh power density of 2.14 W cm−3. • The μMFC stacks power output of 23.6 mW and current output of 194.6 mA are achievable. [ABSTRACT FROM AUTHOR]

The plasma treatment method, which is a simple and ecologically benign procedure, is used to treat the gas diffusion layer (GDL) surface for proton exchange membrane fuel cell (PEMFC) application. The surface plasma treatment greatly aids in the uniform in situ growth of platinum (Pt) nanowires on the GDL surface to fabricate gas diffusion electrodes (GDEs). Helium (He) and nitrogen (N 2) are used, and the outcomes from utilising each gas independently are compared at four different durations between 30 s, 60 s, 90 s, and 120 s. Membrane Electrode Assemblies (MEAs) are fabricated with the as-prepared GDEs and tested in H 2 /air PEMFC single cells. The testing results show the nitrogen plasma applied to the GDE surface for 60 s produces the best power performance with a current density of 1372.7 mA/cm2 at 0.6V. [Display omitted] • The surface of the gas diffusion layer (GDL) was activated using the plasma treatment method. • Carbon papers, whose surface was activated by He and N2 in plasma, were immersed in the prepared Pt solution. • Pt nanowires were allowed to grow on carbon papers. • Membrane Electrode Assemblies (MEAs) were created using as-prepared GDEs as the cathode and purchased GDL as the anode. • As a result of testing the created MEAs, it was seen that the GDL surface activated using N 2 plasma gave better results. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cell (DMFC) and direct ammonia fuel cell (DAFC) have attracted wide attention due to high energy density, environment friendliness, easy availability and transportation of liquid fuel. However, the high cost and low durability of platinum (Pt) impede the large-scale application. Herein, we report a simple and effective approach to develop self-supporting electrodes (SSEs) using the square-wave potential (SWP) electrodeposition method. Compare with conventional electrode, this approach enables the absence of binder, in-situ growth of Pt catalyst on carbon paper, and easily controlled Pt morphologies. Consequently, prepared SSEs exhibit superior catalytic activity and durability toward methanol and ammonia oxidation reactions than the conventional electrode with Pt black as the catalyst. In particular, the SSE with cauliflower-like Pt catalyst exhibits the best catalytic activity and durability. This study suggests that SSE has a great potential in accelerating the practical application of direct liquid fuel cell (DMFC and DAFC). [Display omitted] • Self-supporting electrode was developed by direct growth of Pt on carbon paper. • Different Pt morphologies were obtained by tuning lower potential of SWP method. • Prepared self-supporting electrode exhibited highly efficient Pt utilization. • All electrodeposited Pt showed superior activity and durability for MOR and AOR. • Cauliflower-like Pt catalyst exhibited the highest mass activity and durability. [ABSTRACT FROM AUTHOR]

Microfluidic fuel cells that use microorganisms to oxidize different organic substances to generate electricity are gaining importance due to their versatility to use different fuels. Saccharomyces cerevisiae has used for various purposes due to its capacity to ferment broad spectrum of carbohydrates. In this research, the development of bioanodes based on the immobilization of this yeast was carried out to apply them in the evaluation of a paper lateral-flow microfluidic fuel cell. Immobilization was performed using two different supports, Vulcan carbon and graphene oxide, and four carbohydrates as fuel (saccharose, glucose, fructose, and maltose). The results indicated that the yeast is better distributed and reaches a higher capacity to oxidize carbohydrates when is immobilized on graphene oxide, this bioanode shows better performance in the microfluidic device, reaching a potential above 0.9V when saccharose are used as fuel, representing a promising approach to use microbial bioanodes in small energy conversion devices. • Electrodes based on the Saccharomyces cerevisiae immobilization were used to make paper lateral-flow microfluidic fuel cells. • Immobilization was performed using Vulcan carbon (VC) and graphene oxide (GO) as supports. • Saccharose, glucose, fructose, and maltose were used as fuel in the microfluidic device. • The GO-based bioanode shows better performance, reaching a potential greater than 0.9V when saccharose is supplied. [ABSTRACT FROM AUTHOR]

We herein demonstrate polypyrrole decorated micro-porous laboratory filter paper (PFP) as photoanode (PA) for efficient and stable water splitting. The straddling band position with water redox and the measured band gap of ~1.98 eV, make these PFP-PAs effective for water splitting reactions. The results manifest excellent photo-anodic PEC activity of these PFP-PAs, yielding a photocurrent density of ~9.5 mA/cm2 (at 1.23 V vs. RHE) in a three-electrode configuration. The incident photon-to-current efficiency (IPCE) and applied bias photon-to-current efficiency (ABPE) was measured to be 43.19% and ~1%, respectively. Moreover, the robustness of these flexible PFP-PAs was visualized by the provided stability for more than ~160 min in alkaline conditions. The current study provides a proof-of-concept for the realization of a cost-effective, flexible, and efficient paper-based artificial catalyst (like a natural leaf) for solar-driven water splitting. Image 1 • In-situ fabricated polypyrrole based flexible filter paper photo electrode (PFP-PEs). • Exhibit a bandgap of ~1.98 eV and reported as PEs for water splitting. • Photocurrent density of ~9.5 mA/cm2 (at 1.23 V vs. RHE) in 3-electrode system. • IPCE and ABPE was measured to be 43.19% and ~1%, respectively. • PFP-PEs stable for 160 min in alkaline conditions for PEC water splitting. [ABSTRACT FROM AUTHOR]

Developing efficient and stable non-noble metal oxygen evolution reaction (OER) electrocatalysts for sustainable overall water-splitting is extremely desirable but still a great challenge. Herein, we developed a facile strategy to fabricate Co 3 O 4 –CoOOH heterostructure nanosheet arrays with oxygen vacancies grown on carbon paper (Co 3 O 4 –CoOOH/CP). Benefiting from the unique 3D architecture, large surface area, synergistic effects between Co 3 O 4 , CoOOH and oxygen vacancies, the obtained self-supporting Co 3 O 4 –CoOOH/CP presents excellent electrocatalytic OER activity (low overpotentials of 245 and 390 mV at 10 and 100 mA cm−2) and robust long-term stability in alkaline condition. The present strategy provides the opportunities for the future rational design and discovery of high-performance non-noble metal based electrocatalysts for advanced water oxidation and beyond. [Display omitted] • Co 3 O 4 –CoOOH heterostructure with oxygen vacancies grown on carbon paper was synthesized. • Synergic effect between oxygen vacancies and Co 3 O 4 –CoOOH facilitates the activity. • The Co 3 O 4 –CoOOH/CP exhibited excellent activity and stability for OER. [ABSTRACT FROM AUTHOR]

This study optimizes a novel surfactant-assisted green liquor dregs (GLD) pretreatment of paper mill sludge (PMS), both of which are wastes from the kraft pulping industry, using a combined Response Surface Methodology (RSM) design. Optimized conditions give a maximal reducing sugar release of 16.38 g/L. A substantial reduction in heavy metals aluminum, chromium, cobalt, arsenic, lead, and copper after pretreatment illustrates the enhancement of substrate digestibility by reducing toxic elements. Separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) for hydrogen production are assessed. SSF produced a hydrogen yield of 3.72 mL/g, displaying a 36.26% increase from pretreated PMS compared to SHF. These findings provide insights into possible methods of reducing process duration, energy input, and costs incurred with waste disposal within the paper industry. Furthermore, improved hydrogen yield using an SSF process demonstrates the potential beneficiation of pulp and paper GLD and PMS wastes. • A novel surfactant-assisted GLD pretreatment of PMS developed. • An optimal reducing sugar release of 16.38 g/L was obtained. • Novel pretreatment protocol achieved significant heavy metal reduction. • SSF hydrogen production from pretreated PMS increased hydrogen yield by 36.26%. [ABSTRACT FROM AUTHOR]

The exploration of efficient catalysts toward hydrogen evolution reaction (HER) is still an urgent task. In this paper, Ni/Mo/Cu/C and Ni/Mo/C electrode were obtained by conventional pulse voltammetry, which acted as cathode in microbial electrolysis cells (MECs). The prepared samples are analyzed using SEM, XRD, XPS and electrochemical analysis techniques. Results indicated that the Ni/Mo/Cu coating has a rough and globular structure and presents high current density, a lower Tafel slope of 23.9 mV/dec than 30 mV/dec of Pt, which exceeds the electrochemical activity of Pt electrode. Its remarkably enhanced electrocatalytic activity is attributed to the high surface area, high conductivity as well as synergistic interaction among Ni, Mo and Cu. [Display omitted] • The introduction of Cu to Ni/Mo enhanced synergism among three metals and conductivity of the cathode material. • Results show Ni/Mo/Cu/C electrode has a low Tafel slope of 23.9 mV/dec and excellent kinetics of hydrogen evolution, which exceed Pt electrode. • Ni/Mo/Cu/C exhibit efficient electrocatalysis to hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

The gas diffusion substrate (GDS) is essential in the proton exchange membrane fuel cells. Its fabrication techniques affect the performance significantly and are worthy of investigation. In this study, a manufacturing process of the GDS is proposed to understand the formation process of GDS and promote its structure and performance more pertinently. Different states during the preparation process, raw carbon paper, pre-curing, curing, carbonation, and graphitization, are characterized and measured. Experimental and numerical methods are employed to determine the relationships between microstructure, transport, and mechanical performance variation with the fabricating processes. The results show that its porosity, average pore size, and effective diffusivity decrease first and increase after curing. These parameters after graphitization are lower than that of the carbon paper (CP). The electrical resistivity increases dramatically while pre-curing and decreases gradually after curing, carbonation, and graphitization, and it is much reduced after graphitization. Moreover, mechanical measurement results show that both the picks of tensile strength and flexural modulus occur after curing. Its tensile strength shows little change after graphitization compared to the initial paper's. In contrast, the flexural modulus is improved significantly. • Microstructural characteristics of GDS during fabrication are investigated. • Transport properties and pore-scale simulations for GDS are performed. • Precuring, curing, carbonation, and graphitization on properties are studied. [ABSTRACT FROM AUTHOR]

Paper and pulp mills generate substantial quantities of cellulose-rich sludge materials that are disposed in landfills at a large scale. For sustainability purposes, sludge materials can be bioprocessed to produce renewable fuels and useful chemicals. The enzymatic hydrolysis of cellulose is the process bottleneck that affects the conversion economics directly by using zero-cost raw materials. In order to study and optimize the process, the characteristics of the sludge raw materials should be first evaluated. In this work, sludge samples were obtained from paper mills located at different locations in Wisconsin and Minnesota. Part of the sludge samples was washed (de-ashed) with hydrochloric acid while the other part remained unwashed. The samples were subjected to multiple spectroscopic analyses techniques to evaluate the morphological properties of cellulose fibers and to estimate the total structural carbohydrate content. The results showed that the de-ashing process changed some fiber characteristics and cellulose crystallinity structure in all sludge samples. Sludge sample A (obtained from Kraft pulp and recycled paper mill region) showed a high percentage of fiber, with crystalline cellulose, compared to the other two sludge samples suggesting that sludge A is a valuable source to make value-added products. Aspen Plus mass and energy calculations performed in view of the 'zero' cost and the reliable supply of sludge raw materials producing 2 mol H 2 /mol glucose. Moreover, the results showed that extracting crystalline cellulose from these sludge samples is more profitable than crystalline cellulose made from the other lignocellulosic feedstocks. The results reported here showed that the utilization of these sludge materials would be an economically attractive and promising alternative for the production of hydrogen. Image 1 • A new method for paper mill sludge (PMS) characterization as renewable feedstock. • The deashing step has a major effect on the bioconversion of the PMS. • Studying the crystalline cellulose of the PMS. • A relation between the characterization and potential sugar yield was established. [ABSTRACT FROM AUTHOR]

SO 2 -depolarized electrolysis (SDE) is the key step of the hybrid sulfur (HyS) process, which is one of the simplest thermochemical cycles for producing hydrogen by water splitting. Exploration and optimization of flow field/structure design is essential for improving the efficiency of SDE. In this work, graphite plates with different flow channels, together with porous graphite felts or carbon papers as diffusion layers are adopted to fabricate SDE cells with different structures. Evaluation of the cell structures is carried out, by comparing the SDE performance and taking into account the fluid resistance (pressure drop) of anode side. The effects of graphite felt compression ratio, hydrophilicity or hydrophobicity of carbon papers, anodic fluid flow rate, and operating temperature on the SDE performance are investigated. Square porous flow fields provided by graphite felts show excellent performance. Serpentine channel covered by hydrophobic carbon paper reveals advantages when adopted on the cathode side. Combination of above two flow fields and using them on anode and cathode sides respectively, could achieve excellent SDE performance. Under the condition of 40 °C and 360 mL/min anolyte flow rate, the current density could reach 760 mA/cm2 at the cell voltage of 1.19 V. • 16 SDE cells are fabricated with different flow field plates and diffusion layers. • Performance of electrolytic cells with different structure varies greatly. • Anodic fluid resistance used to assist analysis of performance difference of cells. • Effects of felt compression ratio and carbon paper hydrophobicity are discussed. • High performance achieved by arranging GF & hydrophobic carbon paper properly. [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]

To solve the issues of energy shortage and environmental pollution, it is essential to develop highly effective catalysts for hydrogen evolution reaction (HER) in water electrolysis. Herein, we report a facile and rapid fabrication of a Cu–Co–P catalyst on a carbon paper (CP) substrate using electrodeposition. First, the deposition conditions for Co–P/CP were optimized. The prepared Co–P consisted of numerous spheres and exhibited acceptable catalytic activity towards HER in an alkaline medium with an overpotential of 72 mV at current density of −10 mA/cm2. Further performance enhancement was achieved by the incorporation of Cu to modify the electronic structure of the Co–P catalyst. In a half-cell test, the optimized Cu–Co–P/CP exhibits remarkable performance, achieving −10 mA/cm2 at an overpotential of 59 mV, and the Tafel slope is 38 mV/dec. In a single-cell test, an anion exchange membrane water electrolyzer with a Cu–Co–P/CP cathode and commercial IrO 2 /CP anode exhibited high current density of 0.70 A/cm2 at 1.9 V cell. [Display omitted] • Cu–Co–P was electrodeposited on carbon paper while varying the Cu content. • The catalyst shows low overpotential of 59 mV to deliver −10 mA/cm2 and small Tafel slope in 1.0 M KOH. • The Cu–Co–P/CP gas diffusion electrode exhibited high cell performance (0.7 A/cm2 at 1.9 V cell) in AEMWE single cell. [ABSTRACT FROM AUTHOR]

Growth properties, oxidation-reduction potential kinetics and hydrogen production of Escherichia coli BW25113 parental strain (PS) and hydrogenase (Hyd)-negative mutants were investigated after fermentative growth using office paper waste and cardboard (PW) hydrolysate (PWH). PWH was obtained by using dilute acid method in a steam sterilizer for 1 h, 121 °C. Optimal conditions for bacterial growth and H 2 production were identified (PWH concentrations, pH 7.5). Recording of redox potential using a platinum electrode revealed a drop to −500 ± 10 mV, with a H 2 yield of ~1.45 mmol H 2 L−1 after 4 h of growth using PWH resulted in the formation of 0.20 ± 0.02 g bacterial cell dry weight L−1. Bacterial biomass formation was stimulated ~3-fold upon addition of 0.5% yeast extract, and H 2 production started early - at the beginning of the exponential phase. Moreover, mutants lacking Hyd-1 and Hyd-2 significantly enhanced H 2 production. The findings would be beneficial for the development of H 2 production biotechnology using cheap solid waste materials. • Office waste paper and cardboard hydrolisate (PWH) was upcycled for biomass and biohydrogen. • Dilute acid method in a steam sterilizer, pH adjustment to 7.5 were used for pretreatment. • E. coli wild type yielded H 2 of ~240 mL H 2 (g sugar)−1 at the 4th h of growth. • H 2 production was observed earlier upon 0.5% yeast extract added. • Mutations of hydrogenases Hyd-1 and Hyd-2 enhanced H 2 production. [ABSTRACT FROM AUTHOR]

The use of fossil energy has caused a serious burden on the environment, so it is urgent to find new and developable energy sources. H 2 O 2 as a new type of clean fuel for fuel cell has received widespread attention. In this paper, a novel graphite modified paper based cobalt-cobalt oxalate-nickel (FG@Co–CoC 2 O 4 –Ni) electrode is fabricated by the simple "pencil depicting-electrodeposition-oxalic acid etching-electrodeposition" process for the electrooxidation of H 2 O 2 in alkaline environment. The as-prepared FG@Co–CoC 2 O 4 –Ni electrode owns a novel and special three-dimensional (3D) porous structure, which can greatly increase the diffusion of reactants (NaOH and H 2 O 2) during the electrochemical reaction process and lead a high catalytic activity for the electrooxidation of H 2 O 2. More importantly, three main nanomaterial (Co, CoC 2 O 4 and Ni) and some new generated substances during the CV test in NaOH solution (e.g. Ni(OH) 2 , NiOOH, Co(OH) 2 , CoOOH, Co 3 O 4 and Co 2 O 3 etc.) are on the surface of paper, which will enhance the electrocatalytic activity of the FG@Co–CoC 2 O 4 –Ni electrode to a great extent due to their synergistic effect. When the reaction solution contains 1.0 mol dm−3 NaOH and 0.2 mol dm−3 H 2 O 2 , the FG@Co–CoC 2 O 4 –Ni electrode exhibits a much higher oxidation current density (270.6 mA cm−2) than the FG, FG@Co, FG@Ni, FG@Co–Ni and FG@Co–CoC 2 O 4 electrodes. Besides, the whole preparation process for the FG@Co–CoC 2 O 4 –Ni electrode doesn't use any organic binder, ensuring the electrode owns good conductivity and stability for the electrochemical reaction. At last, the electrocatalytic mechanism for the electrooxidation of H 2 O 2 is discussed. The Ni compounds and Co compounds are believed as the main catalytic substances, and the metallic Co core provides a fast route for the transfer of electrons. The super catalytic activity makes the prepared electrode in this study to be a promising material for the electrooxidation of H 2 O 2 and the novel design idea gives some guidance for the fabrication of electrode materials in the field of fuel cell. [Display omitted] • The environmentally and inexpensive filter paper is used as electrode support. • The 3D porous electrode structure can improve the catalytic performance. • The synergistic effect among complex substances can enhance the performance. • The as-prepared electrode has high catalytic activity at low H 2 O 2 concentration. • The as-prepared electrode has a fast electron transfer path. [ABSTRACT FROM AUTHOR]

Cu-benzene–1, 3, 5-tricarboxylate (Cu-BTC) coating on carbon fiber paper (CFP@Cu-BTC) is synthesized by using the seed-induced hydrothermal method to improve H 2 adsorption capacity, CO 2 /H 2 selectivity, thermal and electrical conductivity of pure Cu-BTC. The electrical conductivity, effective thermal conductivity (ETC), CO 2 and H 2 adsorption capacity of CFP@Cu-BTC composites synthesized for 3, 9, 18, and 24 h are investigated, respectively. Results show the H 2 adsorption capacity of CFP@Cu-BTC (9 h) is similar to that of pure Cu-BTC. The value of the selectivity of equimolar CO 2 /H 2 (18 h) is 58–209 at 0–100 kPa and 273.15 K. The ETC of CFP@Cu-BTC is 17–25 times higher than that of pure Cu-BTC. The electrical conductivity is 1.3 × 1011–1.6 × 1011 times higher compared to that of pure Cu-BTC. The CFP@Cu-BTC composite can be used as a promising material for H 2 storage and electrodes of ultra-capacitor. • Cu-BTC/CFP is obtained by the seeds induced hydrothermal method. • The selectivity of equimolar CO 2 /H 2 (18 h) can reach up to 58–209. • The thermal conductivity of Cu-BTC/CFP is much higher than that of pure Cu-BTC. • The electric conductivity of Cu-BTC/CFP is 1.3 × 105 S/m when loading 40 wt% Cu-BTC. [ABSTRACT FROM AUTHOR]

The present work focused in assessing the hydrogen production from pretreated wastes of the paper industry (PIW) by simultaneous saccharification and fermentation (SSF) using anaerobic biofilms developed in natural fibers (ixtle) at different conditions. Anaerobic sludge from brewery wastewater treatment was used for biofilms and they were developed in plastic spheres covered with fiber cord from ixtle. The solid wastes of paper industry were previously pretreated with H 2 SO 4 at 2.5% (v/v) at 120 °C by 30 min. The solids pretreated were hydrolyzed and fermented in batch reactors. All reactors were kept at an initial pH of 5.0 and three levels of enzyme loadings (10, 40 and 70 FPU/mL) and temperatures (35, 45, 55 °C) were assessed. The maximum hydrogen obtained (60.75 mmol/h*g volatile solids) was at 45 °C and 70 FPU/mL, moreover, no methane was detected in all cases. • SFS is an integral process to produce hydrogen. • Anaerobic sludge useful as inoculum for H2 production. • Effects of temperature/enzyme loading on biohydrogen. • Chemical-thermal pretreatments against methanogens. [ABSTRACT FROM AUTHOR]

The rational design and synthesis of highly efficient, precious metal-free electrocatalysts in the promotion of electrochemical water oxidation is essential for the sustainable use of renewable energy. Herein, an integrated, S-doped MnO x /Mn film developed on carbon paper (CP) formed by a two-step transformation approach that includes template-free electrodeposition and in-situ electrochemical oxidation is employed as an efficient oxygen evolution reaction (OER) electrocatalyst. The doping of S and in-situ electro-oxidation lead to a tailored electronic structure and phase composition, which endow the composite electrode with a significantly enhanced OER catalytic performance. This S-doped integrated electrode perfectly combines highly active MnO x outer layers with conductive metallic Mn inner layers to offer abundant catalytic interfaces and electronic paths, leading to favorable reaction kinetics. As a result, the optimal S-doped MnO x /Mn/CP offers a low overpotential of 435 mV at 10 mA cm−2 with a Tafel slope of 89.97 mV dec−1 as well as improved stability. Impressively, a highly intrinsic catalytic activity with a turnover frequency of 0.0112 s−1 is obtained for S-doped MnO x /Mn/CP, which is 4.2-fold higher than that of MnO x /Mn/CP. S doping plays a critical role in stabilizing the MnIIIO x active phase and is ultimately responsible for the enhanced catalytic performance. This work provides an integrated design concept and S doping approach suitable for boosting the OER catalytic performance of MnO x. A novel S-doped MnO x /Mn/CP integrated electrode formed by a two-step transformation approach that includes template-free electrodeposition and in-situ electrochemical oxidation is employed as an efficient oxygen evolution reaction (OER) electrocatalyst. S doping plays a critical role in stabilizing the MnIIIO x active phase and is ultimately responsible for the enhanced catalytic performance in alkaline media. [Display omitted] • An integrated, S-doped MnO x -based electrode is fabricated with a novel two-step transformation approach. • The as-synthesized S-doped MnO x -based electrode exhibits excellent OER catalytic activity and long-term stability. • The critical role of S doping in stabilizing the MnIIIO x active phase under OER conditions is discussed. • It opens a new avenue in rational design and construction of high-performance S-doped MnO x -based OER catalysts. [ABSTRACT FROM AUTHOR]

A recent commentary by Santhosh and Ravindran on our paper (Int. J. Hydrogen Energy 2014, 39:10,606) demonstrated that the interaction between H 2 and MXene (Sc 2 C and Ti 2 C) phases are not Kubas-type and should be of weak physisorption, and thus made a conclusion that 2D Sc 2 C and Ti 2 C are not suitable for practical hydrogen storage applications. In this responses, we recalculated hydrogen adsorption on 2D Sc 2 C and Ti 2 C by using different exchange-correlation functionals. And based on the calculated results, bare MXenes (especially the Ti 2 C) are suitable as hydrogen storage materials at temperatures of several tens degrees lower than room temperature. And the hydrogen adsorptions on the MXenes terminated with oxygen group were also investigated. Among the Ti 2 C, Sc 2 C and their oxygen-functional counterparts, the binding energy of H 2 on Sc 2 CO 2 surface is the closest to the ideal range of 0.16–0.42 eV/H 2 at ambient conditions, and thus the Sc 2 C with oxygen group is expected to be more suitable as hydrogen storage materials. [ABSTRACT FROM AUTHOR]

Exploring noble-free electrocatalyst for hydrogen evolution by electrolysis of water is significant. Herein, porous Ni(OH) 2 @Ni spherical particles are electrodeposited on carbon papers as efficient electrocatalysts for hydrogen evolution reaction (HER) from water. Due to the porous and composite structure, the HER activity of Ni(OH) 2 @Ni/CP is better than the single phase Ni or Ni(OH) 2 particles on the carbon paper. The overpotential of Ni(OH) 2 @Ni/CP is 106 mV at the current density of 10 mA cm−2 and the Tafel slope is 88 mV dec−1. Moreover, the stability of the catalysts tested for 12 h is also good for HER. Furthermore, the small R ct (1.65 Ω) of Ni(OH) 2 @Ni/CP provides the evident for its excellent catalytic performance. The method of electrodeposition provides the controllable uniform size for porous spherical Ni(OH) 2 @Ni particles. Moreover, the Faradaic efficiency for hydrogen evolution is 100%. Image 1 • The overpotential of Ni(OH) 2 @Ni/CP is 106 mV (10 mA cm−2). • The Tafel slope is 88 mV dec−1 and the stability are good for 12 h. • One-pot preparation of Ni(OH) 2 @Ni/CP via through cyclic voltammetry (CV). [ABSTRACT FROM AUTHOR]

The layered MoS 2 nanostructures have been widely used in the electrochemical hydrogen evolution reaction (HER), but rarely applied in overall water splitting application for their ignorable oxygen evolution reaction (OER) activity. To address this issue, a novel self-standing and bifunctional electrocatalyst, consisting of Co-doped MoS 2 nanosheets anchored on carbon fiber paper, has been prepared via hydrothermal method. Taking advantage of conductive substrate of carbon fiber paper, sufficient-exposed active edges of MoS 2 sheets, and metallic character caused by Co-doping, our electrode exhibits high-efficient bifunctional activities for the overall water splitting in alkaline electrolyte (1 M KOH), which can produce a current density of 20 mA cm−2 at an overpotential of 197 mV for HER and 235 mV for OER. • Mo x Co 1-x S 2 /CFP based Bifunctional Electrocatalyst is synthesized. • The conductivity of MoS 2 can be improved by Co-doping which benefits for HER and OER. • Mo x Co 1-x S 2 /CFP shows good HER activity and excellent OER activity. [ABSTRACT FROM AUTHOR]

Developing efficient and cheap electrocatalysts as substitutes for commercial Pt/C in the oxygen reduction reaction(ORR)is extremely necessary. Herein, paper mill sludge (PMS) was utilized to produce iron, nitrogen and sulfur co-doped carbon nanotube/nanoporous carbon nanocomposite (PMS-CNT/C) by pyrolysis. PMS-CNT/C-b, one of as-prepared PMS-CNT/C exhibited excellent oxygen reduction reaction activity with an onset potential of 0.99 V vs. RHE and half-wave potential of 0.77 V vs. RHE, which was similar to the commercial Pt/C catalyst (onset potential of 0.99 V vs. RHE and half-wave potential of 0.76 V vs. RHE). It had longer-term stability and higher methanol tolerance in alkaline medium than Pt/C. Moreover, the new catalyst also exhibited excellent catalytic performance in neutral solution. The energy output of microbial fuel cells loaded with PMS-CNT/C-b catalyst was also higher than that of commercial Pt/C under neutral condition. The excellent ORR performance of PMS-CNT/C-b was due to the carbon nanotube/nanoporous structure and the synergistic effect of abundant N groups, iron nitrides and thiophene-S. The formation of CNTs in the carbon nanotube/nanoporous carbon nanocomposite was mainly attributed to melamine, which was added into PMS and was at first just considered as a nitrogen source to develop N-doped PMS-based catalysis in this work. The synthesis of paper mill sludge-based carbon nanotube/nanoporous nanocomposite and its excellent ORR activity will make the new catalyst a promising cathodic electrocatalyst alternative for fuel cells. • Paper mill sludge (PMS) was utilized to fabricate Fe, N and S co-doped carbon materials. • Melamine was directly added into PMS to assist the formation of CNTs. • The PMS-based nanocomposites exhibited excellent catalytic activity for ORR. • A green and efficient strategy was developed for the reuse of PMS. [ABSTRACT FROM AUTHOR]

One of the most important problems in dark fermentative hydrogen production is the need for the regulation of the ambient pH due to the formation of volatile fatty acids. For this purpose, alkaline chemicals are usually used; however, alkaline addition to the media increases salt formation, which negatively affects microbial activity. In this study, pH adjustment was performed by providing direct current as an alternative to alkali addition. Experiments were carried out batchwise and electricity was only applied to neutralize the acidic pH value. The waste paper hydrolysate was used as a substrate and the effects of applied voltage (0.25–3 V), substrate concentration (4.8–41.2 g/L at 1 V) and electrode distance (0.3–1.3 cm at 1 V) on hydrogen production performance was investigated. Voltages less than 1 V required too much time to keep the pH convenient and voltages more than 1.5 V adversely affected hydrogen production performance. Providing direct current to the fermentation media significantly reduced the adaptation phase. Conditions for optimal pH adjustment and hydrogen production were obtained at 1 V, 20 g glucose/L and 0.5 cm electrode distance. • Most convenient H 2 production was obtained at 1 V, 20 g glucose/L and 0.5 cm electrode distance. • H 2 was efficiently produced up to 29.1 g glucose/L with DC assistance. • Proper electrode distance enables sufficient electron transfer for pH regulation. [ABSTRACT FROM AUTHOR]

Microfluidic paper based microbial fuel cells (μP-MFCs) have gained considerable popularity due to their compact, quick and low-cost fluid manipulation paradigm. Compared to conventional technologies, paper as a substrate with advanced nanomaterial electrode material has many distinct advantages from point-of-care monitoring to energy harvesting. As a result, these have been used and are more popular in a variety of fields, such as health diagnostics, environmental and food quality management. By this encouragement, herein a portable microbial fuel cell as an origami array has been demonstrated using custom carbon electrodes with a modified the transition metal oxide MnO 2 nanomaterial. This customized electrode design was first printed using a tabletop PCB inkjet printer where the anode was further modified with synthesized MnO 2 nanoparticles. The entire cell was formed by folding the paper along predefined edges where the fuel, Shewanella putrefaciens , was streamed continuously via inherent capillary cation. Various studies, such as morphological, surface catalyst coating, amount loading and volumetric culture optimization experiments, have also been accomplished to find the most appropriate optimum parameter to enhance power conversion efficiency. The developed origami arrayed microbial fuel generated an open-circuit potential (OCP) for two parallel connected MFCs of 0.534 V and a maximum power density of 15.9 μW/cm2 with a maximum current density of 130 μA/cm2. In the end, the harvested power was used by powering the digital watch circuit through the ultra-low DC-DC booster board. Such an MFC origami array, with simple electrode manufacturing and modification process, has a great potential and bright future in Internet of Things (IoT) applications by making multiple stacks where the data can be monitored. [Display omitted] • Origami array-type MFC with printed electrode was fabricated by a PCB inkjet printer. • Several surface modification and loading (MnO 2 and bacteria) optimizations were done. • The developed device generates a maximum power density of 17.5 μW/cm2. • The device was used to power a digital watch using DC-DC booster. [ABSTRACT FROM AUTHOR]

Green and clean energy technologies, including fuel cells, metal-air batteries, water splitting et al., are becoming more significant for our lives. Oxygen reduction reaction (ORR), hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are key reaction processes for fuel cells, metal-air batteries and water splitting. Therefore, it is highly desirable to design a multifunctional catalyst, which owns catalytic performance under a widely applied range. Herein, we demonstrate a novel multifunctional catalyst (Co/Co 3 O 4 @C) by carbonizing a composite material constructed of zeolite imidazolate framework and carbon fiber paper (ZIF-L-Co@CP). It is a carbon-based material containing metallic Co and Co 3 O 4 as a low-cost and effective catalyst toward the ORR and overall water splitting. For ORR, the Co/Co 3 O 4 @C catalyst shows high half-wave potential in both alkaline and acidic media, 0.823 V for 0.1 M KOH and 0.672 V for 0.1 M HClO 4. More importantly, it exhibits good catalytic activities of hydrogen and oxygen evolutions to perform overall splitting in actual seawater. The Co/Co 3 O 4 @C catalyst was prepared by using a composite of ZIF-L-Co nanosheets grown on CP as the precursor, which not only shows excellent activity for ORR in both alkaline and acidic solutions, but also has good ability for overall actual seawater splitting. Image 1 • E 1/2 (0.823 V) of Co/Co 3 O 4 @C catalyst is close to Pt/C in 0.1 M KOH for ORR. • Co/Co 3 O 4 @C catalyst shows excellent ORR performance in 0.1 M KOH and 0.1 M HClO 4. • Co/Co 3 O 4 @C is a good catalyst for overall water splitting in actual seawater. [ABSTRACT FROM AUTHOR]

To design nanostructured photoelectrodes with unique morphology and suitable band structure is a crucial step for potential photoelectrochemical application. For above purpose, the compact Sn 3 O 4 nanoflakes with the smooth surface have been directly grown on carbon paper substrate by a simple hydrothermal method. It is found that the molar ratio of Sn2+ and Sn4+ ions in Sn 3 O 4 nanoflakes can be modulated by the subsequent H 2 O 2 -assisted hydrothermal treatment. The effect of different molar ratio on the energy band has been investigated systematically, together with the evolution of the surface morphology of nanoflakes. Finally, a highly efficient photoelectrode based on Sn 3 O 4 nanoflake has been prepared by the H 2 O 2 -assisted hydrothermal process, which is of larger active surface area and suitable band structure, and therefore exhibits the excellent photocurrent response and photocatalytic performance for H 2 production. The photoelectrode based on Sn 3 O 4 nanoflake displays enhanced photocurrent with 40 μA cm−1 at a basis of 0 V and higher H 2 generation rate with 1.43 × 104 μmol h−1 g−1, much better than those of the original sample. Such superior performance can be probably attributed to the combined effect of unique porous nanoflake-structured, higher active surface area and suitable band structure. • The sample of Sn 3 O 4 nanoflake arrays are prepared via two-step hydrothermal process. • The position of valence and conduction band is found to be dependent on the Sn2+/Sn4+ ratio. • H 2 O 2 -assisted hydrothermal treatment favors to increase the active surface area. • The bandgap of Sn 3 O 4 nanoflake arrays is found to be optimal to absorb visible-light efficiently. • High hydrogen production efficiency can be achieved by adjusting the Sn2+/Sn4+ ratio. [ABSTRACT FROM AUTHOR]

Reforming of hydrocarbon which is an important hydrogen production method proceeds in two steps, i.e. steam reforming and shift reaction. Due to different thermodynamics, the two reactions are conventionally conducted at different temperatures. This study examines one step methane reforming by use of proton-conducting electrochemical cell in combination with a reforming catalyst. Promotion of the reforming reaction was intended by extracting hydrogen via electrochemical hydrogen pumping with a proton conductor cell. In order to compensate for the slow kinetics of the steam reforming, a paper catalyst loaded with Ni was placed in front of the electrochemical cell. Electrolyte support cells were used to verify this concept, and the effect of the electrochemical hydrogen pump was investigated from the composition of the outlet gas. Electrode support cells using a thin film electrolyte was used to reduce overvoltage. It is demonstrated that the steam reforming reaction and the shift reaction take place in one electrochemical cell. Effective catalyst placement and energy efficiency is discussed. Reforming of methane was performed for hydrogen producing with proton conducting SrZr 0.5 Ce 0.4 Y 0.1 O 3-δ (SZCY541) and Ni-loaded paper-structured catalyst (Ni-PSC). When Ni-PSC is used as anode, electrode-supported cell shows enough H 2 evolution rate in agreeing with Faraday's law. Image 1 • Methane reforming was examined using protonic SrZr0.5Ce0.4Y0.1O3-δ electrolyte. • Ni-loaded paper-structured catalyst effectively improved the conversion of CH 4 to H 2. • Electrode-support cell was more effective for steam reforming and the shift reaction. [ABSTRACT FROM AUTHOR]

The surface properties of the anode porous transport layer (PTL) significantly impact the performance of a proton exchange membrane water electrolyzer (PEMWE). The pretreatment (ultrasonic cleaning and acid etching) of a pristine titanium (Ti) felt before it is used as the anode PTL and the surface structural modification of a PTL are two critical methods to improve the performance of an electrolyzer. However, the mechanisms for the pretreatment and surface modification need to be clarified. In this paper, five electrolyzers with five different-fabricated-ways anode PTLs are tested and compared based on I–V curves, EIS curves, and physical characterization techniques. X-ray photoelectron spectroscopy (XPS) results show that the ultrasonic cleaning pretreatment of PTL can improve hydrophilicity by increasing the amount of hydroxyl. In addition, EIS results indicate the significant charge transfer resistance of electrolyzer taking pristine titanium felt as PTL. Adopting the carbon paper as a microporous layer (MPL) or treated titanium felt with acid etching can eliminate or reduce the charge transfer resistance of the electrolyzer. Finally, the mechanism of surface pretreatment and modification of PTL are disclosed to cast light on the improvement of PTLs in further study. • Mechanisms of pretreatments and surface modifications for PTLs are investigated. • Electrolyzers with different-fabricated-ways anode PTLs are tested and compared. • Ultrasonic cleaning strengthens the hydrophilicity of the PTL. • Supplementing MPL or acid pretreatments can improve the anode charge transfer. • Improved mass and electron transport are the reasons for the improved performance. [ABSTRACT FROM AUTHOR]

The rapid development of the portable and wearable devices has inspired the ever-growing pursuit of flexible energy storage equipment which can power these devices. Here, rice paper (RP) was integrated with a homemade LGS-polypyrrole (LGS-PPy) ink and commercial pen ink in order to construct a flexible electrode of a supercapacitor via a facial dip-coating method. The obtained RP/LGS-PPy ink/Pen ink composites showed a high areal specific capacitance of 1568 mF/cm2 at 0.2 mA/cm2, owing to the uniform deposition of a LGS-PPy layer which was covered by the pen ink coating. Furthermore, the assembled symmetric supercapacitor fabricated from the RP/LGS-PPy ink/Pen ink electrode exhibited impressive electrochemical performances in terms of specific capacitance (317.5 mF/cm2 at 2 mA/cm2), power density (846 μW/cm2 at the energy density of 23.5 μWh/cm2), and life times (82.1% capacitance retention after 5000 cycles). In addition, the capacitance of the as-prepared device remained essentially unchanged even after bending at 180°, thus demonstrating this device's outstanding flexibility. The low cost of raw materials, robust fabrication strategy as well as the moderate performances make the RP-based supercapacitor a promising candidate for future flexible energy storage devices. [Display omitted] • RP/LGS-PPy ink/pen ink was constructed via a facial dip-coating method. • The RP-based electrode exhibited outstanding desirable areal specific capacitance and excellent cycling stability. • The RP-based electrode demonstrated impressive flexibility. • The assembled supercapacitor showed superior energy density and power density. [ABSTRACT FROM AUTHOR]

This work examines the feasibility of co-gasification of sewage sludge and paper-mill sludge in a commercial scale plant and its application for sludge-to-energy conversion. The results indicated that the thermal reaction activity is increased with an increase in the amount of sewage sludge. This is due to the sewage sludge contains less fixed carbon content could decrease the activation energy, resulting in a thermal reaction is significantly enhanced. The synthetic gas (syngas) composition, that includes H 2 and CO, ranged from percentages of 2.59%–4.13% and 3.2%–6.91%, respectively. The heating value of the produced gas ranged from 1.67 MJ/Nm 3 to 2.56 MJ/Nm 3 , which was coupled with cold gas efficiency (CGE) that ranged from 46.6% to 77%. In the case of two tons of wet tested sludge with 67% moisture content, it could produce one ton of dry tested sludge with 30% moisture content after a drying process, and produce approximately 2.2 tons of syngas in gasification. After using a boiler and heat exchanger for energy recovery, it is possible to recover 4.46 tons of steam. This steam could provide energy for the dryer, and constitutes a positive sum on the energy balance in a commercial scale gasification plant. [ABSTRACT FROM AUTHOR]

The present work demonstrates a miniaturized, easily fabricated, environment-friendly, and cost-effective Microfluidic Paper-based Microbial Fuel Cell (MPMFC) as a potential Energy Harvesting Device. The device consists of a microchannel with a reductant (Shewanella putrefaciens exoelectrogen bacterium with L.B Broth) and oxidant (aerated tap water) flowing over Carbon electrode (anode) and Silver electrode (cathode) using co-laminar flow with the self-capillary phenomenon. The electrochemical analysis like Polarization, Open Circuit Voltage (OCV) was evaluated using a potentiostat, and conductivity and sheet resistance were evaluated using a four-point probe instrument. Various bacterial studies, like growth curve study (Optical Density), volumetric concentrations, and incubation time, were carried out to find out the best suitable optimal bacterial conditions. Lastly, detailed element composition study and morphology of the surface of the electrode with biofouling was carried out using Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) techniques, respectively. The portable MPMFC yields a maximum power density of 15.4 μW/cm2 (1340 nA/cm2) at 390 mV over 90 μL of culture. Also, An Internet of Things (IoT)/cloud-based hardware has been developed and integrated with MPMFC platform to observe the real-time device performance leading to its long-lasting potential to operate miniaturized microelectronics sensors and portable devices. • A miniaturized Membraneless Paper-based Microbial Fuel Cell has been discussed. • The device has been powered by Shewanella Putrefaciens exoelectrogen bacterium. • Various studies were performed to find out the best suitable bacterial conditions. • Rigorous electrochemical analyses were evaluated to explore the device outputs. • Maximum power density of 15.40 μW/cm2 (1.34 μA/cm2) at 390 mV was obtained. [ABSTRACT FROM AUTHOR]

In this paper, ceria flowers containing nano-sized catalyst Ni particles were prepared on alumina-silica fiber network for production of hydrogen from biogas. The CeO 2 flowers were prepared using hydrothermal method and then NiO was loaded on the CeO 2 flowers by impregnation method. The Paper-structured catalysts (PSCs) were prepared from alumina-silica fibers and the CeO 2 –NiO flowers using conventional paper making method. The loaded NiO particles were uniformly dispersed on the CeO 2 flowers with the use of polyvinylpyrrolidone as a dispersion enhancer, which was observed by FE-SEM and EDX analysis. The NiO particles were then reduced into Ni by using H 2. The PSCs containing CeO 2 –Ni flowers with various Ni contents (2.1, 3.4, and 4.6%) were used for dry reforming of CH 4. It was found that 3.4% amount of Ni on the PSC was suitable for reforming reaction, and the higher amount of Ni (4.6%) did not increase the CH 4 conversion. The PSC with the CeO 2 flowers had porous structure and large surface area leading to the better dispersion of the Ni particles with smaller size. This helped increase in catalytic performance, prevention of agglomerated particle catalysts at high temperature and coke forming after a long time operation. The CH 4 conversion of the PSCs containing CeO 2 –NiO flowers in the dry reforming of CH 4 was much higher (nearly 90%) with a smaller Ni content in comparison with the PSC without the CeO 2 flowers (with higher Ni content of 8.6%). Moreover, the PSCs with the flowers exhibited an excellent catalytic stability with the degradation of CH 4 conversion of only 3.1% after 50 h of reforming. In addition, the high oxygen storage capacity and oxygen mobility of CeO 2 resulted in a partial removal of coke forming on the catalyst particles during reforming. This indicated that the catalytic activity of the Ni particles dispersed on the CeO 2 flowers for dry reforming of CH 4 was superior to that of various Ni-based catalyst systems which had much higher Ni contents. Therefore, it is possible to use the PSCs containing CeO 2 –Ni flowers to generate hydrogen for use as fuels from dry reforming of CH 4. Image 1 • 5 μm spherical CeO2 flowers had open porous structure and high surface area. • NiO particle catalysts were uniformly dispersed on the CeO2 flowers. • Paper-structured catalysts (PSC) with the dispersed flowers had a great porosity. • PSCs with small Ni content exhibited excellent catalytic activity in CH4 reforming. • PSCs exhibited degradation of CH4 conversion of only 3.1% after 50 h of reforming. [ABSTRACT FROM AUTHOR]

Transition-metal chalcogenides as the promising alternatives to noble-metal-based electrocatalysts for hydrogen evolution reaction (HER) with high activity and durability in water splitting have attracted extensive attention in recent years. Herein, Co z Ni y S x @PPy composites with three-dimensional (3D) cauliflower-like were firstly prepared on carbon fiber paper (CFP) via a simple and efficient electrochemical reduction of elemental sulfur in the precursor of S@PPy composite coated on CFP to react with Co and Ni ions in the electrolyte. The optimum electrode, i.e., Co z Ni y S x @PPy/CFP-6 (A-6) prepared by using an electrolyte with a Co/Ni molar ratio of 0/6, showed excellent catalytic activity (with an overpotential of 185 mV@10 mA cm−2 and a small Tafel slope of 78.13 mV dec−1) as well as long-term stability (at least 100 h) in 1 M KOH solutions. This work provides a novel way to fabricate effective and non-noble-metal electrodes for HER in water splitting. Image 1 • An electrochemical reduction of sulfur way is used to prepare the TMCs. • The relationship of nickle and cobalt in the volcano plot is proved by experiment. • The mixed crystals of Ni y S x strengthen catalytic activity and stability of HER. [ABSTRACT FROM AUTHOR]

Ultra-thin carbon paper (CP) has attracted considerable interest for pursuing miniaturization and high-flux for fuel cells. This paper reports an ultra-thin CP (0.11 mm) fabrication process for proton exchange membrane fuel cell (PEMFC). Graphene oxide (GO) was dispersed in the phenolic resin (PF) impregnant, and later was coated on the carbon fiber (CF) in order to improve the performance of the resulting CP. The results demonstrated that compared with the CP, the GO-modified CP exhibited the increasing of carbon yield and crystallinity of matrix carbon, improving of tensile strength and electrical conductivity because of the more covalent bond (C O and C O) formed between the PF (GO) and carbon fiber. Meantime, the porosity and permeability of CP decreased with the increasing of GO in impregnant. The contact angle of GO-modified CP was slightly larger than CP. In all the CP with 1 wt% GO had superior properties (The tensile strength reached 31 MPa and the electrical resistivity decreased to 2.1 mΩ cm). [ABSTRACT FROM AUTHOR]

In this study, waste paper was used as the raw material for hydrogen gas production by dark fermentation at different initial substrate and cell concentrations. Glucose obtained from acid hydrolyzed waste paper was used at six different concentrations between 3.84 and 45.5 gL −1 to determine the effects of sugar concentration on bio-hydrogen production. The highest cumulative hydrogen gas was obtained at 18.9 gL −1 initial sugar concentration. Sugar concentrations above 18.9 gL −1 resulted in product inhibition. Similarly, the initial biomass concentration was varied between 0.25 and 2 gL −1 while sugar concentration was kept constant at 18.58 ± 2.45 gL −1 to determine the effects of initial biomass concentration. The highest cumulative hydrogen gas production was obtained with the initial biomass concentration of 0.5 gL −1 . The highest hydrogen yield (140 ml H 2 g −1 total sugar) was observed at 3.84 gL −1 total sugar concentration. Hydrogen yield decreased with increasing initial sugar concentration due to inhibition by volatile fatty acids (VFAs) produced by dark fermentation and furan derivatives produced from acid hydrolysis of waste paper. [ABSTRACT FROM AUTHOR]