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Developing cost-effective and stable materials for the electrocatalysis of hydrogen evolution reaction (HER) remains challenging. In this study, efficient catalysts for HER were synthesized by integrating the cobalt and molybdenum oxides via electrodeposition, followed by subsequent sulfurization of the as-prepared oxides using chemical vapor deposition (CVD). This methodology allowed the incorporation of both cobalt and molybdenum components into the catalyst in a single step. The as-synthesized CoSx@MoSx/MoOx-based catalysts exhibited excellent hydrogen production performance in acidic media owing to the presence of Co-S and Mo-S bonds in the hybrid structure. Particularly, CoSx@MoSx/MoOx(90@360) and MoSx@CoOx(180@180) displayed the best HER performances with low overpotentials of 80 mV and 150 mV, respectively. The catalysts were highly stable, with their stability preserved for over 1000 cycles with marginal reduction in overall efficiency. Therefore, these findings suggest the potential of CoSx@MoSx/MoOx and MoSx@CoOx composites as ideal candidates for developing low-cost catalysts for electrochemical hydrogen production. [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]

Thermodynamically favorable selective electrooxidation reactions coupled with hydrogen evolution reaction (HER) is a promising strategy for simultaneous production of value-added chemicals and hydrogen. In this work, a binder-free gold nanoflowers electrode based on carbon paper is prepared and used as anode catalyst, which results in good charge transfer, high stability and superior catalytic activity for electrooxidation of glycerol. We develop an integrated system of glycerol electrooxidation with HER, and the effect of potential on the distribution of anodic electrooxidation products and cathodic hydrogen production are investigated. At 1.0 V, the overall reaction reaches 10 mA cm−2 and the selectivity of glyceric acid (GLA) reaches 97.2%. At 1.2 V, hydrogen production reaches the highest value of 960 μmol L−1 and the anode product consists of a mixture of glyceric acid, glycolic acid (GA) and formic acid (FA). At 1.3 V, the selectivity of FA reaches 87.3%. Operando technique in situ infrared spectroscopy is used to monitor the immediate evolution and study the pathway of controlled glycerol electrooxidation. This work demonstrates carbon paper is a promising substrate material of binder-free electrode applied in thermodynamically favorable electrocatalytic reactions boosting hydrogen evolution. [Display omitted] • A binder-free electrode based on carbon paper is developed. • Hydrogen production is increased by 24 times with the addition of glycerol. • The selectivity of glyceric acid on carbon paper supported gold nanoflowers is 97.2%. • In situ FTIR reveals the pathway for electrooxidation of glycerol. [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]

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]

Biohydrogen and biomethane production via two stage sequencing system from paper mill effluent (PME) was evaluated to enhance its COD reduction. Heat-shock pretreatment of anaerobic sludge at 90 °C for 15 min was chosen to obtain a mixed microbial inoculum for dark fermentative hydrogen production. The effect of initial pH (5, 6 and 7) on the efficiency of hydrogen fermentation at different concentrations of substrate (3, 5 and 7 g-COD/L) was investigated, which the maximum hydrogen yield was obtained at initial pH 5. After that, the effects of substrate concentration (3, 5, 7, 10 and 15 g-COD/L) and fermentation temperature (37 and 55 °C) were investigated on the hydrogen production yield. The efficiency of dark hydrogen fermentation for all substrate concentrations was higher at 55 °C. The hydrogen production was enhanced as substrate concentration increased up to 5 g-COD/L, but then it was reduced, and the optimum hydrogen yield of 38.8 mL H 2 /g-COD initial was obtained at substrate concentration of 5 g-COD/L at 55 °C. The highest hydrogen (35.1 mL H 2 /g-COD initial) was obtained at 5 g-COD/L and 55 °C and the highest methane (553.8 mL CH 4 /g-COD initial) was obtained at 3 g-COD/L and 37 °C. Maximum COD reduction of 88.1% was obtained in two-stage sequencing dark fermentation/anaerobic digestion system at 3 g-COD/L and 37 °C. • BioH 2 and bioCH 4 were generated in expend of COD reduction from PME. • Effects of initial pH, COD loading and temperature were studied. • Primary step dark fermentation showed higher hydrogen yields at 55 °C. • Max COD reduction 88.1% was obtained in 2-stage sequencing system (3 g-COD/L, 37 °C). • 38.8 mL H 2 /g-COD initial at 55 °C and 553.8 mL CH 4 /g-COD initial at 37 °C were obtained. [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]

Hydrogen sulfide (H2S) is known to participate in bacteria-induced inflammatory response in periodontal diseases. Therefore, it is necessary to quantify H2S produced by oral bacteria for diagnosis and treatment of oral diseases including halitosis and periodontal disease. In this study, we introduce a paper-based colorimetric assay for detecting bacterial H2S utilizing silver/Nafion/polyvinylpyrrolidone membrane and a 96-well microplate. This H2S-sensing paper showed a good sensitivity (8.27 blue channel intensity/μM H2S, R2 = 0.9996), which was higher than that of lead acetate paper (6.05 blue channel intensity/μM H2S, R2 = 0.9959). We analyzed the difference in H2S concentration released from four kinds of oral bacteria (Eikenella corrodens, Streptococcus sobrinus, Streptococcus mutans, and Lactobacillus casei). Finally, the H2S level in Eikenella corrodens while varying the concentration of cysteine and treatment time was quantified. This paper-based colorimetric assay can be utilized as a simple and effective tool for in vitro screening of H2S-producing ability of many bacteria as well as salivary H2S analysis. [ABSTRACT FROM AUTHOR]

A crucial factor in advancing the broad utilization of electrocatalytic hydrogen evolution reaction (HER) is the development of efficient catalysts with sufficient active sites. Herein, a hydrothermal approach is utilized to fabricate helical chain stacked two‐dimensional (2D) tellurium (Te) nanoflakes, whose HER performance hasn't been systematically studied yet. It is found that Te nanoflakes transferred on carbon fiber paper (CFP) exhibit impressive HER properties and show a load dependence. The overpotential required for HER is significantly reduced to 279 mV under a load condition of 0.86 mg cm−2 at a current density of 10 mA cm−2. Density functional theory (DFT) calculations are further systematically carried out on Te catalytic sites along the helical chain at [0001] direction with a threefold screw symmetry. It is found that the Gibbs free energy of adsorbed hydrogen atom (ΔGH*) on Te sites is significantly lower than that of molybdenum disulfide (MoS2). Besides, the active sites based on surface atom density calculation reveal that Te provides more adsorption sites than layered MoS2. The decreased adsorption energy and efficient adsorption sites in Te may highlight the promising application of elemental crystal Te in electrocatalytic hydrogen production and pave the way for developing new types of electrocatalysts. [ABSTRACT FROM AUTHOR]

In an attempt to explore high efficient and cheap electrocatalyst for water splitting hydrogen production, small molybdenum carbide nanoparticles with the size about 3–6 nm are loaded on three-dimensional N-doped carbon matrix successfully with ammonium heptamolybdate ((NH 4 ) 6 Mo 7 O 24 ·4H 2 O) and filter paper as precursor by pyrolysis. Due to its small size, large surface area and high conductivity, this electrocatalyst shows excellent activity in hydrogen evolution reaction (HER). In acid media, its overpotential to achieve a current density of 10 mA·cm −2 is as low as 167 mV, with Tafel slope is only 73 mV·dec −1 . The electrocatalyst also shows large exchange current density (j 0 ) with the value 0.15 mA·cm −2 . Furthermore, it shows excellent durability after 1000 cycles of long-term test, and the catalytic current remains stable over 10 h at fixed overpotential. This work elucidates a feasible strategy to obtain efficient electrocatalysts with cheap and naturally sustainable material as precursor and shed some light on the exploration and optimization of electrocatalysts in energy chemistry. The HER of this electrocatalyst is studied and the results illustrate it exhibits a stable hydrogen evolution rate of 44.5 μmol·h −1 with faradaic efficiency about 100%. [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]

This study reports on the synthesis and characterization of an effective cathode paper electrode comprising comparatively inexpensive hydrous RuO 2 (h-RuO 2) nanoparticles on carbon nanotubes (CNT) for anion exchange membrane (AEM) water electrolysis. The concentration of hydrous RuO 2 nanoparticles on the CNT was varied to assess their impact on the electrocatalyst for the hydrogen evolution reaction (HER). The electrocatalytic performance of h-RuO 2 /CNT comprising 22.0 wt% of Ru was evaluated. Promising results were obtained, with a current density of −10 mA/cm2 at only 36 mV of overpotential and a mass activity of −2.41 A/g Ru at 100 mV. Additionally, we conducted first-principles calculations to compare the HER catalytic activities of crystalline RuO 2 and hydrous RuO 2 with varying vacancies and to determine the H 2 O concentration in the structural lattice using free-energy diagrams. The study findings demonstrate that the h-RuO 2 /CNT paper can be used as an efficient electrocatalyst for AEM water electrolysis. [Display omitted] • A highly efficient HER catalyst decorated hydrous RuO 2 (h-RuO 2) nanoparticles on carbon nanotubes (CNT) was prepared. • The paper electrode composed of h-RuO 2 /CNT network structure improved conductivity and achieved excellent HER properties. • This paper electrodes applied to high-efficiency AEM water electrolysis as cathode. [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]

• The hygroscopic property of paper fiber is used to prepare a bifunctional catalyst. • The impregnation time for preparing the hollow microtubular Ni-MgO-CaO is 1 min. • 94.1 % of hydrogen is stably produced on 5Ni-10MgO-CaO from biogas for 50 cycles. • Only 37.1 % loss of the sorption-enhanced effect is shown during the entire cycle. Sorption-enhanced steam reforming (SESR) process is a promising technology aiming at the production of high purity hydrogen with CO 2 capture. The key to the success of this process is the availability of high-performance bifunctional catalysts. Herein, we develop a hollow microtubular Ni-MgO-CaO bifunctional catalyst with paper fiber as template. Due to the strong hygroscopic properties of paper fibers, it provides a method for the rapid synthesis of catalysts with design components by adsorbing solution. The characterizations indicate that the impregnation time (1 min vs 24 h) has no effect on the structural properties of Ni-MgO-CaO bifunctional catalysts. MgO as an inert spacer can weaken the sintering of CaO to ensure a stable CO 2 uptake. Moreover, the agglomeration of Ni particles is inhibited by the MgO coating on their surface. 5Ni-10MgO-CaO as the best performing catalyst displays high stability for the SESR of biogas (SESRB) reaction, during which 94.1 % purity of hydrogen with a 95.2 % conversion of CH 4 is stably produced and only 37.1 % decrease of sorption-enhanced effect is observed in 50 SESRB-calcination cycles. [ABSTRACT FROM AUTHOR]

Pulp and paper mill effluent (PPME), a rich cellulosic material, was found to have great potential for biohydrogen production through a photofermentation process. However, pretreatments were needed for degrading the complex structure of PPME before biohydrogen production. The aim of this study was to gain further insight into the effect of an ultrasonication process on PPME as a pretreatment method and on photofermentative biohydrogen production using Rhodobacter sphaeroides NCIMB. The ultrasonication amplitudes and times were varied between 30–90% and 15–60 min, respectively, and no dilution or nutrient supplementation was introduced during the biohydrogen production process. A higher biohydrogen yield, rate, light efficiency and COD removal efficiency were attained in conditions using ultrasonicated PPME. Among these different pretreatment conditions, PPME with ultrasonication pretreatment employing an amplitude of 60% and time of 45 min (A60:T45) gave the highest yield and rate of 5.77 mL H 2 /mL medium and 0.077 mL H 2 /mL h, respectively, while the raw PPME without ultrasonication showed a significantly lower yield and rate of 1.10 mL H 2 /mL medium and 0.015 mL H 2 /mL h, respectively. The results of this study demonstrated the potential of using ultrasonication as a pretreatment for PPME because the yield and rate of biohydrogen production were highly enhanced compared to the raw PPME. Economic analysis was also performed in this study, and in comparison with raw PPME, the highest net saving was $0.2132 for A60:T45. [ABSTRACT FROM AUTHOR]

Solar-driven water splitting by inorganic semiconductor photocatalysts is considered a promising method to produce hydrogen fuel. Loading inorganic semiconductor on cellulose fiber to construct photocatalytic paper contributes to the dispersion and recycling of photocatalyst. In addition, the photocatalytic paper floating on water can build a solid–gas biphase photocatalytic interface (photothermal-generated steam/photocatalytic paper/hydrogen), replacing the traditional liquid–solid–gas triphase photocatalytic interface (liquid water/photocatalyst/hydrogen) for improving photocatalytic kinetics. Here, we design and synthesize a photocatalytic composite paper with zinc sulfide (ZnS) anchored onto cellulose fibers (CF) with the help of polydopamine (PDA). PDA achieves high load and uniform distribution of ZnS on cellulose fibers, and forms the ZnS/PDA heterojunction to increase photogenerated charge separation efficiency and photocatalytic stability. Solid–gas biphase photocatalytic interface constructed by the CF/PDA/ZnS composite paper minimizes the interface barriers of hydrogen transport and water molecular adsorption for improving hydrogen evolution rate. The CF/PDA/ZnS composite paper shows a high hydrogen production rate up to 18706.8 μmol h−1 g−1. Stable loading of ZnS/PDA heterojunction in composite paper contributes to the photocatalytic stability. In the third photocatalytic cycle, the hydrogen evolution rate of CF/PDA/ZnS composite paper remains 96.4%. This work inspires that anchoring of inorganic semiconductor on cellulose fibers with the help of PDA can be a promising strategy for designing efficient photocatalytic paper for solar hydrogen production. [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]

Following the example of photovoltaics, one approach to large‐scale photocatalytic hydrogen production is the irradiation of a correspondingly large catalyst area. Paper production is a process in which large areas can already be produced based on the main component: cellulose. Herein, the TiO2 photocatalyst modification PC500, which also uses platinum nanoparticles as a cocatalyst, is supported in two different ways using cellulose. On the one hand, the catalyst is fixed to the surface of a commercial filter paper and, on the other hand, a photocatalytic paper is produced. For comparison, the catalyst is immobilized by means of drop coating using Nafion and measured as a suspension. The cellulose‐stabilized films are active and hydrogen production is comparable with the activity obtained from the drop‐coating method. The experiments show that the aggregation behavior of cellulose can be used to produce photocatalytically active films. The preparation is easy and can be applied to different kinds of (photo)catalysts. Although the films are very active, their stability during reaction due to swelling and hydrogen production must be further improved. [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]

Improving the reaction interface is imperative for increasing catalyst utilization and enhancing overall cell performance in proton exchange membrane electrolyzer cells (PEMECs). Herein, a thin Nafion-carbon-mixed microporous layer coated carbon paper (Nafion-C MPL/CP) is first developed as an efficient cathode liquid/gas diffusion layer for PEMECs. With the Nafion-C MPL/CP, low cell voltages of 1.64, 1.74 and 1.84 V are delivered, which are 50, 80 and 140 mV lower than those of the conventional bare carbon paper at 2, 4 and 6 A/cm2, respectively, achieving about 3-fold higher catalyst utilization. Meanwhile, superior performance is also demonstrated compared to the commercial PTFE-C MPL/CP. The remarkable performance of the Nafion-C MPL/CP should be attributed to the enhanced reaction interface, which not only provides rich active sites with abundant electron and proton transport pathways for the electrochemical reaction but also reduces the interfacial contact resistance and mass transport losses. Moreover, excellent stability of the Nafion-C MPL/CP is demonstrated at a current density of 1.8 A/cm2 with no performance degradation during over 100-h operation. Due to the enhanced reaction interface with significantly improved catalyst utilization, the developed Nafion-C MPL/CP shows great potential to reduce the hydrogen production cost and accelerate PEMEC commercialization. [ABSTRACT FROM AUTHOR]

To counteract expensive cathodes, a single chamber microbial electrolysis cell (MEC) equipped with nanoporous oxide coating on a carbon paper electrode as a cathode was explored. The performance of the MEC was evaluated based on the chemical oxygen demand (COD) removal efficiency, catalytic activity, and hydrogen production. The obtained results indicated that nanoporous oxide coated carbon electrode with TiO 2 achieved maximum H 2 yield (3.0 mol H 2 mol−1 acetate), followed by ZrO 2 and SiO 2. In contrast, the uncoated carbon electrode achieved lower hydrogen yield (0.08 mol H 2 mol−1 acetate). A maximum COD removal of 82% was achieved from the carbon electrode coated with TiO 2 followed by 80.5% from SiO 2 and 79% from ZrO 2. Additionally, based on linear sweep voltammetry, nanoporous oxide coated electrodes started H 2 evolution at a lower potential than the uncoated electrode, thereby exhibiting a higher catalytic rate. This investigation showed that carbon electrodes with nanoporous coating can be one of the economical (low cost) and potential electrodes to be used as a cathode in the MEC for hydrogen production instead of expensive metallic electrodes. [Display omitted] • Low-cost, high potential cathode electrodes were explored. • Nanoporous oxide coated electrodes exhibited high catalytic activity. • Efficient H 2 production with low applied potential. • H 2 yield was higher for nanoporous coated electrodes than uncoated. [ABSTRACT FROM AUTHOR]

In this research, we carried out the process of simultaneous saccharification and fermentation (SSF) of paper industry wastes with/without chemical pretreatment, using reactors in batch with anaerobic biofilms developed in spheres covered with ixtle fiber cord. Biofilms were previously developed a UASB reactor using anaerobic sludge with acid/thermal pretreatment to remove hydrogen consuming bacteria. Subsequently, the process of saccharification and simultaneous fermentation (SSF) of paper industry waste without chemical pretreatment was evaluated using batch reactors with developed anaerobic biofilms. The key process parameters were: pH (4, 5 and 6) and enzyme loading of Celluclast enzyme (10, 40 and 70 FPU) at a temperature of 45° C The results for hydrogen production with paper industry wastes without pretreatment showed optimal working conditions to maximize hydrogen production by SSF process at: pH (5) and an enzyme load of 70 FPU, so the maximum hydrogen yield obtained was 31.188 mmol/h × gSV. The results obtained from the evaluation of the process of SSF performed with paper industry wastes subjected to chemical pretreatment with H 2 SO 4 2.5% showed the optimum working conditions to maximize hydrogen production: pH (4), an enzyme load of 70 FPU, the maximum value of hydrogen yield obtained was 55 844 mmol/h *gSV. The key process parameters were optimized by the response surface methodology (RSM) based on a two factor-three level central composite design (CCD), using as variables: pH (4.5 and 6), enzyme loading of Celluclast ® (10, 40 and 70 UPF) and temperature (45 °C), for paper industry wastes with/without acid pretreatment. The results showed the analysis of variance was performed to test the importance of the polynomial equation of second order, so equations obtained for both residues (with/without pretreatment) describe the hydrogen yield in this study. [ABSTRACT FROM AUTHOR]

Abstract: Paper and pulp industry effluent was enzymatically hydrolysed using crude cellulase enzyme (0.8–2.2FPU/ml) obtained from Trichoderma reesei and from the hydrolysate biohydrogen was produced using Enterobacter aerogenes. The influence of temperature and incubation time on enzyme production was studied. The optimum temperature for the growth of T. reesei was found to be around 29°C. The enzyme activity of 2.5FPU/ml was found to produce about 22g/l of total sugars consisting mainly of glucose, xylose and arabinose. Relevant kinetic parameters with respect to sugars production were estimated using two fraction model. The enzymatic hydrolysate was used for the biohydrogen production using E. aerogenes. The growth data obtained for E. aerogenes were fitted well with Monod and Logistic equations. The maximum hydrogen yield of 2.03mol H2/mol sugar and specific hydrogen production rate of 225mmol of H2/g cell/h were obtained with an initial concentration of 22g/l of total sugars. The colour and COD of effluent was also decreased significantly during the production of hydrogen. The results showed that the paper and pulp industry effluent can be used as a substrate for biohydrogen production. [Copyright &y& Elsevier]

• Self-supporting x Ni-WC@CFP catalysts with fold-like structure were prepared through one-step molten salt method. • 4M Ni-WC@CFP showed excellent HER activity in 0.5 M H 2 SO 4 (overpotential of 73 mV at 10 mA cm−2 and Tafel slope of 66.4 mV dec−1). • The increasing concentration of Ni(NO 3) 2 promoted first and then inhibited the catalytic performance of x Ni-WC@CFP electrocatalysts, resulting from the synergistic effect of Ni and W on hydrogen adsorption energy. Exploring high-performance and inexpensive electrocatalysts for hydrogen evolution reaction to substitute Pt-based compounds is important to sustain hydrogen production. Herein, WC based self-supported catalysts doped with different concentration of nickel nitrate solution (Ni(NO 3) 2) were synthesized on carbon fiber paper (CFP) by one-step molten salt method (abbreviated as x Ni-WC@CFP). With the increasing of Ni(NO 3) 2 concentration, fold-like structures were formed on the catalysts, which was conducive to active sites exposure. As Ni(NO 3) 2 concentration increased from 1M to 5M, the catalytic performance of the electrocatalyst showed a trend of increasing first and then decreasing. The optimal 4M Ni-WC@CFP showed comparable catalytic ability in 0.5M H 2 SO 4 with a low overpotential of 73 mV at 10 mA cm−2 and Tafel slope of 66.4 mV dec−1. However, excessive nickel doping would inhibit HER performance. The density functional theory calculation further verified the experimental results. The adsorption energy of hydrogen showed a decreasing trend with the rising amount of Ni doped in, while the W-H binding energy would change in an opposite direction as over doped Ni. This work provided an insight for the preparation of high-efficiency self-supported W-based electrocatalysts and expounded the influence trend of Ni doping concentration on the performance of electrocatalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Evaluation of dark fermentative hydrogen production using paper mill effluent (PME) • Investigation of the impact of different HRTs on the biofilm reactor performance. • H 2 production rate was enhanced to 6.21 L H 2 d−1 L−1 by decreasing HRT to 2 h. • Max. yield of H 2 was 0.96 mmol H 2 g−1 COD at 8 h HRT. • Production of VFAs as valuable by-products as well as COD removal. This study assessed the feasibility of continuous hydrogen production in an anaerobic packed bed biofilm reactor (APBR) using paper mill effluent (PME) without any pretreatment or modification. To form a microbial biofilm on supports, the reactor was seeded with a thermal pretreated anaerobic sludge. After the start-up stage, under mesophilic conditions and pH control, the system performance in the case of hydrogen production as biofuel and VFAs as valuable by-products as well as COD removal was investigated at different hydraulic retention times (HRTs) (24, 16, 12, 8, 4, 2 and 1.2 h). The highest hydrogen concentration in the produced gas was 41.5 % obtained at HRT 4 h. The highest hydrogen production rate and yield were 6.21 L H 2 d−1 L−1 at HRT 2 h and 0.96 mmol H 2 g−1 COD at HRT 8 h, respectively. With decreasing the HRT from 24 to 1.2 h, the OLR was increased from 27.35 to 547 g COD L−1 d−1 that positively affect the hydrogen production rate for all HRTs except for the shortest HRT. Furthermore, COD removal efficiency was reduced from 25.2 to 6 %. Low value of COD removal efficiency is because of conversion of organic inlet to valuable metabolites such as VFAs in the effluent. [ABSTRACT FROM AUTHOR]

Pulp and paper industry is a water-intensive industry. This industry commonly produces considerable amount of effluent, especially from virgin raw materials processing. The effluent, namely pulp and paper mill effluent has the potential to adversely affect the receiving watercourses. However, the nutrients in the pulp and paper mill effluent could be reused as a substrate in biohydrogen production. In this study, photofermentative biohydrogen production was investigated using Rhodobacter sphaeroides and pulp and paper mill effluent as a substrate. An application of low power ultrasound on R. sphaeroides was predicted to increase photofermentative biohydrogen production but excessive ultrasound effects might inhibit the production due to possible cell disruption. Hence, various ultrasonication duration (5, 10 and 15 min) and amplitude (15%, 30% and 45%) were applied on the bacteria to determine the recommended ultrasonication conditions for improving biohydrogen production. The recommended conditions were operated at ultrasonication amplitude and duration of 30% and 10 min, respectively. A maximum biohydrogen yield of 9.62 mL bioH 2 /mL medium was obtained under this condition, which was 66.7% higher than the result obtained using R. sphaeroides without undergoing ultrasonication (control). The light efficiency and cell concentration were increased by 67% and 150%, respectively, using ultrasonication amplitude and duration of 30% and 10 min, respectively as compared to the control. The present results demonstrated that moderate power of ultrasonication applied on R. sphaeroides was an effective method for enhancing photofermentative biohydrogen production using raw pulp and paper mill effluent as a bioresource. [ABSTRACT FROM AUTHOR]

Pulp and paper industry primary sludge being largely composed of lignocellulosic fibres, it could be used as carbon source by bacteria having cellulolytic capability. The aim of this study was to evaluate the use of cellulose contained in this type of sludge for Clostridium thermocellum to produce ethanol, hydrogen and cellulases. In an ATCC 1191 medium containing 5 kg m −3 dry primary sludge from recycled paper mill, batch culture reached stationary phase after 2 days. All of the available cellulose was hydrolysed after 60 h of incubation, with a final pH of 5.83. Metabolites produced after 60 h of fermentation were acetate (8.50 mol m −3 ), ethanol (11.30 mol m −3 ), lactate (8.75 mol m −3 ), formate (0.27 mol m −3 ), hydrogen (11.20 mol m −3 ) and carbon dioxide (18.41 mol m −3 ). Cellulase activity was detected in the supernatant after 36 h, with a maximal activity of 0.25 U cm −3 at 72 h. Pulp and paper primary sludge appeared to be a readily usable substrate for C. thermocellum at this concentration, yielding both potential biofuels (hydrogen and ethanol) as well as active cellulases. [ABSTRACT FROM AUTHOR]

The urea oxidation reaction (UOR), which possesses a low theoretical potential and superior kinetics, is an attractive substitute for the anodic oxygen evolution reaction (OER) in overall water splitting; however, the implementation of hydrogen production in overall urea splitting is impeded by the deficiency of highly efficient, durable and cost-effective catalysts. Herein, we fabricated an Ni2P–MoP2 heterostructure with a hierarchical structure grown on carbon paper (Ni–Mo–P/CP), which exhibited robust activity and outstanding durability for the electrocatalytic oxidation of urea. The Ni–Mo–P/CP catalyst possessed an ultralow potential of 1.39 V to obtain the current density of 100 mA cm−2, small Tafel slope (27 mV dec−1) and long-term durability with almost no decay within 15 h. The experimental characterization revealed that the optimized electronic structure and the synergistic effect of abundant exposed active sites in the Ni–Mo–P/CP catalyst contribute to the efficient UOR catalytic activity. This work enriches the candidate catalysts for the UOR and promotes the industrial development of hydrogen production. [ABSTRACT FROM AUTHOR]

The improvement of batch photofermentative biohydrogen production was investigated using ultrasonication pre-treatment on a combined effluent of palm oil and pulp and paper mills. The effects of the amplitude (30–90%) and ultrasonication duration (5–60 min) were investigated in terms of their influences on the biohydrogen yield and chemical oxygen demand (COD) removal. The recommended ultrasonication parameters were found at the higher ranges of amplitude and duration (A70T45). Using A70T45 ultrasonication, the production of biohydrogen at 30 °C could be enhanced up to 8.72 mL H 2 /mL medium , with a total COD removal of 36.9%. During pre-treatment at A70T45, an energy input of 775 J/mL was supplied to disintegrate complex compounds into simpler structures. As a result, an increase in the soluble organic matter concentration was achieved, which led to enhanced biohydrogen production. On the other hand, the lowest biohydrogen yield (4.67 mL H 2 /mL medium ) and total COD removal (28.8%) were obtained in the control without pre-treatment. The enthalpy of the photofermentation process was estimated to be 141.1 kJ/mol with a threshold temperature of 30.9 °C based on a modified Arrhenius approach. [ABSTRACT FROM AUTHOR]

Biomass-based hydrogen production is an innovative approach for realizing carbon-neutral energy solutions. Despite their promise, both structures differ in terms of the biomass energy domain, which is at the entry point of the technology, and the hydrogen energy domain, which is at the exit point of the technology. In this study, we conducted structural and predictive analyses via cross-domain bibliometric analysis to clarify the differences in the structures and perspectives of researchers across domains and to suggest ways to strengthen collaboration to promote innovation. Our study revealed that the hydrogen energy domain has a balanced impact on realizing a hydrogen society using biomass-based hydrogen production technology, while the biomass energy domain has a strong interest in the process of processing biomass. The results reveal that different communities have different ideas about research, resulting in a divide in the areas to be achieved. This comparative analysis reveals the importance of synergistic progress through interdisciplinary efforts. By filling these gaps, our findings can lead to the development of a roadmap for future research and policy development in renewable energy and highlight the importance of a unified approach to sustainable hydrogen production. The contribution of this study is to provide evidence for the importance of cross-disciplinary cooperation for R&D directors and policy makers. [ABSTRACT FROM AUTHOR]