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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.

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 H2/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.

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. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

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 H2SO4 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.

Cost-effective, simple and flexible hydrogen gas sensors operating at room temperature were demonstrated based on DC magnetron sputtered palladium thin films. The main idea is to use commercial microfiber filtration paper as a cheap, fibrous and flexible substrate for palladium. With this objective, Pd thin films with 21, 38 and 54 nm thicknesses were deposited and characterized by grazing incident X-ray diffraction (GIXRD) and scanning electron microscope (SEM). The gas sensing behavior was tested by hydrogen gas in the concentration rang of 0.5–10%. GIXRD showed a PdX/Pd phase and SEM revealed existing of many structural nanocracks. An activation process was needed where sensors were heated up to 110 °C in the presence of 10% H2. Then a desirable hydrogen sensitivity with good stability based on hydrogen induced lattice expansion (HILE) effect in which conductance increases was observed. However, for low Pd thicknesses (21 and 38 nm) and at below 4% H2, an inverse effect was observed in which the conductance decreased instead of increasing. For all samples the response time is incremental in the range of 0.5–4% and declining for 4–10%. Moreover, the deposited Pd sensors operate well when they are bent inward or outward. The governed physical mechanism was expressed and discussed.

A recent commentary by Santhosh and Ravindran on our paper (Int. J. Hydrogen Energy 2014, 39:10606) demonstrated that the interaction between H2 and MXene (Sc2C and Ti2C) phases are not Kubas-type and should be of weak physisorption, and thus made a conclusion that 2D Sc2C and Ti2C are not suitable for practical hydrogen storage applications. In this responses, we recalculated hydrogen adsorption on 2D Sc2C and Ti2C by using different exchange-correlation functionals. And based on the calculated results, bare MXenes (especially the Ti2C) 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 Ti2C, Sc2C and their oxygen-functional counterparts, the binding energy of H2 on Sc2CO2 surface is the closest to the ideal range of 0.16–0.42 eV/H2 at ambient conditions, and thus the Sc2C with oxygen group is expected to be more suitable as hydrogen storage materials.

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 IrO2/CP anode exhibited high current density of 0.70 A/cm2 at 1.9 Vcell.

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.

Flexible and lightweight reduced graphene oxide wrapped Si/carbon fibers paper (Si@RGO/CFP) anodes have been prepared by pyrolysis of the common filter paper, which was soaked into the suspension containing graphene oxide and Si. The reduced graphene oxide wrapped Si nanoparticles (Si@RGO) homogeneously distributed on the interlaced carbon fibers and void among the carbon fibers. The Si@RGO/CFP as a flexible binder-free electrode exhibits an initial reversible capacity of 2055 mAh g −1 and 1092 mAh g −1 after 100 cycles for Si@RGO at 100 mA g −1 along with good rate performance. The superior electrochemical performance of the Si@RGO/CFP is attributed to the interconnected carbon fibers substrate, which provides electronic conduction pathways and works as mechanical support, and the void among carbon fibers accommodates the volume changes of Si and maintains the integrity of the electrode materials.

This paper reports a novel synthesis route to prepare an integrated gas diffusion electrode (I-GDE) consisting of self-supported N-doped nanonet by pyrolyzing polyaniline on carbon paper via the electrodeposition of aniline. Electrochemical experiments suggest that the integrated structure apparently improves the mass transport, electrical conductivity in the oxygen reduction reaction performance. The peak current density of the I-GDE achieves 0.71 mA cm −2 , which is almost two times to the conventional ink-based electrode fabricated with the same material under the same conditions.

As the softest part in a proton exchange membrane fuel cell (PEMFC), the gas diffusion layer (GDL) could have a large deformation under assembly pressure imposed by bipolar plate, which would have an impact on the cell performance. So, there is an urgent need to clearly reveal the mechanical behavior of GDL under certain pressure. In this paper, the mechanical behavior of paper-type GDL of PEMFC is studied, considering the complex contact environment in the fibrous layered structure. The microstructure of GDL is reconstructed stochastically, then the stress-strain relationship of GDL is explored from the perspective of solid mechanics by using the finite element method. Based on microstructure morphology, it is found that contact pairs and pore space of microstructure are two key factors determining the nonlinearity of the compressive curve. The equivalent Young's modulus increases with the decrease of porosity and carbon fiber diameter but it is not very sensitive to the carbon paper thickness. The results indicate that with the increase in acting pressure, the average porosity of the carbon paper decreases, and the nonuniformity of porosity along the through-plane direction increases. Furthermore, a reasonable explanation for the increase of concentration loss and the decrease of ohmic loss is given from the microstructure findings of the present study.

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.

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 CeO2 flowers were prepared using hydrothermal method and then NiO was loaded on the CeO2 flowers by impregnation method. The Paper-structured catalysts (PSCs) were prepared from alumina-silica fibers and the CeO2–NiO flowers using conventional paper making method. The loaded NiO particles were uniformly dispersed on the CeO2 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 H2. The PSCs containing CeO2–Ni flowers with various Ni contents (2.1, 3.4, and 4.6%) were used for dry reforming of CH4. 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 CH4 conversion. The PSC with the CeO2 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 CH4 conversion of the PSCs containing CeO2–NiO flowers in the dry reforming of CH4 was much higher (nearly 90%) with a smaller Ni content in comparison with the PSC without the CeO2 flowers (with higher Ni content of 8.6%). Moreover, the PSCs with the flowers exhibited an excellent catalytic stability with the degradation of CH4 conversion of only 3.1% after 50 h of reforming. In addition, the high oxygen storage capacity and oxygen mobility of CeO2 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 CeO2 flowers for dry reforming of CH4 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 CeO2–Ni flowers to generate hydrogen for use as fuels from dry reforming of CH4.

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/Co3O4@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 Co3O4 as a low-cost and effective catalyst toward the ORR and overall water splitting. For ORR, the Co/Co3O4@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 HClO4. More importantly, it exhibits good catalytic activities of hydrogen and oxygen evolutions to perform overall splitting in actual seawater.

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.

In this work, a paper-based hydrogen fuel cell is developed without the need for hydrogen storage. Instead, an embedded aluminum foil inside the paper is utilized for in-situ hydrogen generation. The electrodes and current collectors are also deposited on the paper, leading to a lightweight, compact and flexible hydrogen fuel cell with an OCV reaching 0.93 V and a peak power density of 4 mW cm−2. Benefited from the impeded hydroxyl ion diffusion, the hydrogen generation rate is well controlled, leading to a high faradaic efficiency of 72%. In addition, the cell can be operated under different bending angles with negligible power loss. Furthermore, it can be conveniently stacked in the same piece of paper for higher voltage and power outputs. Such a novel fuel cell design is especially suitable for powering various flexible devices with small rated power.

The anomalous heat effect reported in the paper, “Excess heat evolution from nanocomposite samples under exposure to hydrogen isotope gases” by Kitamura et al. published in the Int. J. Hydrogen Energy 43, pp. 16,187–16,200 (2018), is investigated in the science of the cold fusion phenomenon (CFP) established in these 30 years. It is concluded that the effect is a normal event in the CFP consistent with many events observed in materials with various components and compositions composed of host elements and hydrogen isotopes.

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.

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 H2 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 H2 yield of ~1.45 mmol H2 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 H2 production started early - at the beginning of the exponential phase. Moreover, mutants lacking Hyd-1 and Hyd-2 significantly enhanced H2 production. The findings would be beneficial for the development of H2 production biotechnology using cheap solid waste materials.

In Lithium-air cathode, graphene containing materials have been reported as ideal cathode materials due to their large theoretical specific surface area, chemical stability, high electrical conductivity and charge capacity. In this study; three free-standing flexible graphene cathodes were produced with different thickness by vacuum filtration technique. For preparation of the graphene electrodes, graphene oxide (GO) papers were chemically reduced. Surface morphology of the produced graphene cathodes were characterized using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) was conducted to understand elemental composition of the GO paper. X-ray diffraction (XRD) technique and Raman spectroscopy were carried out to investigate the structure of the GO paper electrode. Moreover, specific surface area and porosity distribution of the GO paper was performed using Brunauer-Emmett-Teller (BET) method from N-2 adsorption and desorption isotherms and the pore size were calculated using the Barrett-Joyner-Halenda (BJH) algorithm on the desorption branch. Electrochemical performance of the freestanding graphene electrodes were assessed in ECC-Air test cell from 1.5 V to 4.5 V at a constant current density. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

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 (ηE) of 93% at the same current density, which is slightly higher than untreated CPs (ηE = 91%). Cycling the system 10 times also results in higher ηE and UE for rGOHTFM CP (ηE = 92% and UE = 99% on average) in comparison to untreated electrodes (ηE = 86% and UE = 97% on average). In comparison the widely investigated SGL 10AA CP has lower efficiencies and utilization as expected (ηE = 74% and UE = 83% on average).

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, CozNiySx@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., CozNiySx@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.

A flexible paper-structured catalyst (PSC) that can be applied to the anode of a solid oxide fuel cell (SOFC) was examined for its potential to enable direct internal reforming (DIR) operation. The catalytic activity of three types of Ni-loaded PSCs: (a) without the dispersion of support oxide particles in the fiber network (PSC-A), (b) with the dispersion of (Mg,Al)O derived from hydrotalcite (PSC B), and (c) with the dispersion of (Ce,Zr)O2-δ (PSC C), for dry reforming of CH4 was evaluated at operating temperatures of 650–800 °C. Among the PSCs, PSC-C exhibited the highest CH4 conversion with the lowest degradation rate. The electrochemical performance of an electrolyte-supported cell (ESC) was evaluated under the flow of simulated biogas at 750 °C for cases without and with the PSCs on the anode. The application of the PSCs improved the cell performance. In particular, PSC-C had a remarkably positive effect on stabilizing DIRSOFC operation fueled by biogas.

Hu et al. reported the hydrogen storage properties of Sc2C and Ti2C based MXene phases utilizing density functional theory (DFT) as implemented in the CASTEP code [1, 2]. Based on such calculations, the authors suggest that the MXenes should be a new family of potential hydrogen storage media. Their results claim a maximum hydrogen storage capacity of 9.0 wt% with an average binding energy of 0.164 eV/H2 in Sc2C MXene indicating Kubas-type interaction between H2 and the MXene. These investigations are of prime importance since they provide insight about further applications of MXenes for hydrogen storage. In these calculations they have used local density approximation (LDA) to estimate the adsorption energies. However, binding energies for H2 with the MXene phases mentioned above obtained from more accurate calculations based on Generalised Gradient Approximation (GGA) and calculation including dispersion correction (GGA + vdW) show very weak binding energy ( ∼ 0.064 e V / H 2 ) suggesting weak physical interactions between H2 and the MXene phases. Our accurate DFT calculations predict that these MXene phases are not suitable for hydrogen storage at realistic conditions. So we conclude that appropriate exchange-correlation functional should be used to extract hydrogen adsorption energies in nano-phases to describe their hydrogen storage properties reliably.

A paper-structured catalyst (PSC) for biogas reforming was prepared with the aim of improving coking tolerance. During the paper-making process using inorganic fibers, Ni-loaded (Ce,Zr)O2–δ particles were synthesized via co-precipitation and subsequent chemical reduction (on-paper synthesis). The effects of the CeO2/ZrO2 weight ratio during preparation and the Ni loading amount on the catalytic activity for dry reforming of CH4 were investigated at 750 °C. A Ni loading of 6 wt% with CeO2/ZrO2 ≥ 1 led to stable CH4 conversion of 85% without coking under a gas hourly space velocity of 3800 h−1. The oxygen storage capacity of the (Ce,Zr)O2–δ particles dispersed in the inorganic fiber network may contribute to the oxidation of carbonaceous species deposited on the catalyst surface.

A layered binary Mn-Fe oxide as bi-functional electro-catalyst with nanopetals morphology is grown on porous carbon paper for the first time via one-step electrodeposition process. The electrocatalyst is characterized by X-ray diffraction, scanning electron microscopy (SEM) and energy dispersive spectroscopy analysis. SEM analysis demonstrates notable morphology viz. nanopetals of the Mn-Fe oxide grown on carbon paper. The electrocatalytic activity is checked for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline medium. Rotating disk electrode (RDE) voltammetry is carried out to study the ORR kinetics, which proves that ORR process follows four-electron pathway in alkaline medium. Oxygen evolution reaction study reveals that it has higher activity for OER with a lower onset potential of 1.6 V vs RHE and higher current density of 11.5 mA/cm2 at 2.0 V vs RHE reference electrode.

This work presents the integration of a paper-based microfluidic fuel cell inside a lateral flow assay-human immunodeficiency virus (HIV) test. To modify the HIV test, a bioanode that oxidizes the glucose present in a serum or blood sample and a cathode that reduces the oxygen delivered from air were stacked on the bottom and top, respectively, of a paper-strip test. A mixture of glucose oxidase enzyme, Nafion®, glutaraldehyde, deionized water and tetrabutylammonium bromide were deposited on a methylene blue electro-polymerized Toray® paper and used as the bioanode. Meanwhile, Pt/C (Vulcan XC-72) on Toray® paper was used as an air-breathing cathode. The GOx enzyme anchored on the carbon-based surface was examined by scanning electron microscopy. The electrochemical response of the bioanode array demonstrated the oxidation of 0.1 M glucose, leading to a current density increase due to FAD+/FADH reactions. The above procedure was corroborated through scanning electrochemical microscopy, which showed an increase in the current (400 pA) in the presence of glucose on the bioanode. The paper-based microfluidic fuel cell performance showed power densities of 0.16 and 0.12 mW cm−2 using human serum and blood samples, respectively. Furthermore, the stability of the device was measured in terms of the recovery after obtaining four polarization curves that lasted 30 min, after which the sample dried out. This work represents a great advancement in the integration of a paper-based microfluidic fuel cell towards autonomous lateral flow assays.

Among numerous noble-metal-free electrocatalysts, molybdenum sulfides are recognized as promising candidates for hydrogen evolution reaction (HER). Owing to abundant under-coordinated sulfur atoms serving as catalytically active centers, intensive spectra studies have revealed that the HER property of amorphous molybdenum sulfide (a-MoSx) is superior to crystal molybdenum sulfide (c-MoS2). In this work, nitrogen-doped active carbon (NAC) is obtained through plasma treatment and amorphous MoSx/NAC hybrid catalyst films are electrodeposited on carbon fiber papers (CFP) which are employed as porous three-dimensional electrodes with low resistivity. The incorporation of NAC increases the electrochemically active surface area, enhances the electron transport, and facilitates the reaction kinetics. Moreover, the functionality durability benefits from synergistic effect between a-MoSx and NAC. Thus, the obtained hybrid catalyst delivers the excellent HER activity, requiring only 203 mV overpotential to achieve a geometrical current density of 100 mA cm−2 with a Tafel slope of ∼43.9 mV per decade.

A binder-free and flexible Au electrode is prepared by spontaneous deposition of Au onto a A4 (A4-paper)-8B (8B pencil)-Ni Film substrate (ABNi) which is assembled by electrodeposition of nanoscale Ni particles on the surface of A4 paper coated by 8B pencil. The morphology and phase structure of the (A4-paper)-8B (8B pencil)-Ni Film-Au (ABNiAu) electrode are characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer and X-ray diffractometer. The catalytic activity of the ABNiAu electrode for NaBH 4 electrooxidation is investigated by means of cyclic voltammetry and chronoamperometry. The electrode exhibits a high electric conductivity and the activity substance attaches to the surface of paper substrate tightly and does not fall off at all and the nanoscale Ni and Ni Au alloy enhance the broken of the B H bond in the BH 4 − , all of which lead to a high catalytic activity for NaBH 4 electrooxidation. The oxidation current density reaches 300 mA cm −2 in 1 mol dm −3 NaOH and 0.1 mol dm −3 NaBH 4 at −0.2 V. The exchanged electrons (n) is 6.0 (8.0 in theory), which indicates that the ABNiAu electrode has much higher utilization efficiency of the fuel than our reported LaNi 5 /Pd (n = 4) electrode.

In order to improve the hydrogen sensing of transition metal oxide nanomaterials at room temperature, MoO3 nanowire paper was prepared and used as a hydrogen sensing materials on substrate. In this paper, orthorhombic phase, ultra-long (∼1 mm) MoO3 nanowires were synthesized through conventional hydrothermal method at 260 °C for 96 h. A flexible nanowires paper with size of 200 mm × 300 mm was obtained by further self-assembly formation process of pure α-MoO3 nanowires in aqueous solution on hydrophobic substrate, and the thickness of paper can be controlled depend on the concentration of disperse nanowires. A novel hydrogen sensor with sensing area of 10 mm × 10 mm was obtained after Pt interdigital electrodes (IDE) deposited on the surface of α-MoO3 nanowires paper and transferred into ceramic circuit board (CCB) without any surface modification. The response and recovery time are about 3.0 and 2.7 s toward 1.5% H2, respectively. The sensors also show good selectivity toward H2 against other reduce gas, such as C2H5OH, CO and CH4. Large amounts of the porous structures and high specific surface of nanowires paper is beneficial to the absorption of oxygen molecules, which would lead to the high sensitivity, fast response and recovery speed of sensor at room temperature. MoO3 nanowires paper sensors have excellent stability and reliability, which could work for 5.56 years at room temperature.

Sulfonated poly(ether ether ketone) (SPEEK) membranes have been deposited on the both sides of a sulfonic acid functionalized graphene oxide (SGO) paper to form a proton exchange membrane (PEM) with a sandwiched structure. The obtained SPEEK/SGO/SPEEK membrane could exhibit proton conductivity close to Nafion ® 112 and lower methanol permeability. The use of this SPEEK/SGO/SPEEK membrane greatly improves the performance of the semi-passive direct methanol fuel cell (DMFC). The semi-passive DMFC with the SPEEK/SGO/SPEEK membrane is found to be capable of delivering the peak power density 60% higher than that with the commercial Nafion ® 112. This, along with its comparable durability to Nafion ® 112, strongly suggests the great promise of using the SPEEK/SGO/SPEEK membrane as the PEM.

A 3D multiphase lattice Boltzmann model (LBM) was established and employed to study the impact of polytetrafluoroethylene (PTFE) content and distribution on the liquid–gas transport in proton exchange membrane fuel cell (PEMFC) carbon-paper gas distribution layer (GDL). In the computer-generated carbon paper GDL, part of the fibers’ surface was randomly specified as PTFE to achieve a desired PTFE content and distribution. For non-uniform PTFE distribution cases, a GDL sub-region neighboring to gas channel (GC) was set to have higher PTFE content. PTFE content and distribution show important influence on the liquid–gas flow and on the relationship of relative permeability versus phase saturation. The GDL sub-region of more PTFE acts like a capillary barrier and raises the liquid saturation level in the rest part of GDL. The simulated liquid saturation level in GDL diminishes with the increase of PTFE content in GDL. The liquid phase relative permeability is larger in the GDL of lower PTFE content if the (overall) liquid saturation is lower than a threshold value, whereas it becomes smaller if the liquid saturation is higher than this threshold value. The liquid phase relative permeability in the GDL with non-uniform PTFE distribution is reduced when the liquid saturation in GDL is lower than a certain value, but when the liquid saturation is higher than this value, it is larger compared with that in the GDL with uniform PTFE distribution. The gas phase relative permeability in the GDL of lower PTFE content is larger than tat in the GDL of higher PTFE content and the non-uniform distribution of PTFE in GDL slightly reduces the gas phase relative permeability value.

“Mass transfer in catalyst supports”and “reactive sites”are two critical factors for supported thin film catalysts. Based on such considerations, paper composed of cellulose fibers (CFs) is chosen as a competent nano-catalyst carrier because its broad porous structure is conducive to mass transfer. Then a facile aquatic synergistic synthesis is developed to decorate polypyrrole (PPy) encapsulated palladium nano-composites onto the CF paper structures. The pyrrole monomers (Py) reduce Pd 2+ to Pd nanoparticles in aqueous solution, and meanwhile the Pd 2+ initiates the polymerization of Py to PPy. In the as-prepared composite paper catalysts, the broad pores constructed by the microfibers facilitate the reactant diffusion and the Pd/PPy nanoparticles supported on the fibers provide more reactive sites for catalysis. As a result, the catalytic activity for hydrolysis of ammonia borane is improved. The H 2 turnover frequency is 21.1 mol H 2 mol Pd −1 min −1 , surpassed most other Pd based film catalysts. Importantly, excellent stability and reproducibility are also realized by the immobilization of Pd NPs by PPy layers onto fibers.

The present discussion concerns some doubtful results included in the above paper.

The present discussion concerns some doubtful results included in the above paper.

Algal biomass is considered as an alternative raw material for biofuel production. The search for new types of raw materials including high-energy types of microalgae remains relevant, since the share of motor fuels in the world energy balance remains consistently high (about 35%) with the oil price characterized by high volatility. The authors have considered the advantages of microalgae as raw materials for fuel production. Biochemical and thermochemical conversion are proposed as technologies for their processing. The paper presents the results of the study on the pyrolysis of the biomass of the blue-green microalgae/cyanobacterium Arthrospira platensis rsemsu 1/02-P clonal culture from the collection of the Research Laboratory of Renewable Energy Sources of the Lomonosov Moscow State University. The experimental investigation on the pyrolysis process of microalgal biomass has been carried out with the experimental setup made at the Institute of High Temperatures RAS in pure nitrogen 6.0 to create an oxygen-free medium with a linear heating rate of 10°С/min from room temperature to 1,000°С. The entire pyrolysis process has proceeded in the endothermic region. The specific values for solid residue, pyrolysis liquid and gaseous products have been experimentally determined. The following products have been manufactured by pyrolysis of microalgal biomass weighing 15 g: 1) char with a solid residue mass of 2.68 g, or 17.7% of MAB initial mass (while 9.3% of MAB initial mass has remained in the reactor); 2) pyrolysis liquid with a mass of 3.3 g, or 21.9% of initial mass; 3) noncondensable pyrolysis gases, 1.15 L. The specific volumetric gas yield (amount of gas released from 1 kg of RM) has amounted to 0.076 nm³/kg. In the paper, the analysis of the composition and specific volumetric yield of non-condensable pyrolysis gases produced in the pyrolysis process depending on temperature has been carried out. It is shown that the proportion of high-calorific components of the gas mixture (hydrogen, methane and carbon monoxide) increases with the temperature increase. The heating value assessment for the mixture of these gases has been performed as well.

In this study, the colemanite (a natural calcium borate mineral, NCBM) and Fe2O3 used as a catalyst on the liquefaction of Elbistan Lignite (EL, which has the most reserves in the east of Turkey). The liquefaction experiments were carried out at the reaction temperature of 400 °C, the reaction time of 90 min, the solvent/solid ratio of 3/1, stirring speed of 400 rpm, and initial nitrogen gas pressure of 20 bar. Fe2O3 and colemanite were together prepared as a new catalyst. Research has been made the recent observation that the highest liquefaction product yields, especially from a series of valuable fractions, obtained, with the highest mineral content of lignite. According to that model colemanite mixed with Fe2O3 to decide if the mineral content effect on total conversion if mineral substances added separately from coal. Fe2O3 selected as the most suitable catalyst type. To understand how to affect colemanite (as an economical catalyst source and also has high reserves in Turkey) as a catalyst on the liquefaction of EL with waste paper. The experiment conditions fixed and so compared due to the total conversion values. Unlike previous studies, this study was 67.1% of the total fluid conversion without catalyst, but this value increased to 77.6% when 15% NCBM catalyst was used. The total conversion was up to 83.8% with the catalyst concentration of 3% Fe2O3. On the other hand, when only 3% of Fe2O3 was used, the total conversion was only 75%. As a result, the mixture of NCBM and Fe2O3 increased the liquefaction efficiency by 15% by the synergistic effect.

Decreasing carbon dioxide (CO2) emission by converting to higher-valued product has become of interest. Hydrogen (H2) is an important feedstock required in thermochemical conversion of CO2 to chemicals such as methanol. The cost and availability of H2 affect the cost of CO2 conversion. This study is focused on the process simulation of H2 production from ethanol feedstock. Steam reforming of ethanol is compared with dehydrogenation of ethanol to H2 with valued products including ethyl acetate and acetaldehyde. Form this study, steam reforming of ethanol presents the lowest cost of H2 production at 1.58 USD/kg H2 while dehydrogenation of ethanol presents the cost at 3.24 and 1.97 USD/kg H2, respectively. Although presenting the lowest cost, steam reforming of ethanol provides a net positive CO2 emission in the overall CO2 conversion to methanol process. In contrast, ethanol dehydrogenation to H2 and byproducts, ethyl acetate and acetaldehyde, promotes a net negative CO2 emission of −819.20 kg/ton methanol and −5.42 kg/ton methanol, respectively. The results present a decreasing CO2 emission with an increasing cost of H2 production.

Palm oil mill effluent (POME) is a wastewater effluent that is generated from palm oil milling. Treatment of POME, especially using biological treatment methods, is a challenge as it contains high amounts of organic and sulfur compounds, and it is highly acidic. In this research, the effects of zero-valent iron (ZVI) on the enhancement of methane production from POME via anaerobic digestion were investigated. Furthermore, to identify the reactor operation modes that were suitable for the addition of ZVI, anaerobic digestion of POME was tested in three reaction configurations: batch reactor, fed-batch reactor, and continuous stirred-tank reactor (CSTR). In the batch mode, where acidic POME was fed with 16 g/L of ZVI dose just once, methane production increased by 74%. However, as the oxidation of ZVI under anaerobic conditions led to the production of hydroxyl ions, the pH of the medium continuously increased from approximately 7 to 9, which is not suitable for methanogenesis. In the fed-batch mode that involved intermittent feeding of acidic POME, the pH of the culture media was maintained at 6.8. This is because the extra hydroxyl ions generated from the oxidation reaction of ZVI tended to neutralize the acids in the feeding substrate. In addition, ZVI promoted the production of methane from POME and increased the average methane content in biogas from 62% to 76%. In the CSTR mode, which involved continuous feeding of acidic POME, ZVI increased methane production by 86% (from 1.79 to 3.32 L/day), methane content in biogas from 60 to 75%, and total chemical oxygen demand (tCOD) removal efficiency from 78 to 89 to 88–95%. Thus, the addition of ZVI can be a potential strategy for in-situ methane enrichment of biogas by anaerobic digestion of POME. This is because ZVI acts as a buffer for acid generation and provides extra electrons, ferrous ions, and ferric ions, which promote key microbial activities in the anaerobic digestion process.

Herein, dark fermentation (DF, V = 5.5 L) and subsequent mesophilic methanogenesis (V = 43.5 L) are run as expanded granular sludge bed reactors (EGSB) at thermophilic (υDF = 60 °C) and hyperthermophilic (υDF = 80 °C) temperatures. A synthetic glucose wastewater is run with a 22.5 g/L chemical oxygen demand (COD) and 48–9 h hydraulic retention times (HRTs), giving organic loading rates (OLRs) of 11–60 g COD/L/d for DF. The maximum hydrogen production rate (HPR) is HPR = 3.0 m³/m³/d for HRT = 9 h with a 50 L/kg COD hydrogen yield (HY) and 40 vol% H2. Methane production rate (MPR) reaches MPR = 2.6 m³/m³/d with 70 vol% CH4 at HRT = 2.8 d. The highest H2 yields are HY = 180 L/kg COD with 53 vol% H2 (thermophilic, HRT = 48 h). Hyperthermophilic temperatures led to lower HPRs (0.7 m³/m³/d) and MPRs (1.6 m³/m³/d). 53% of Thermoanaerobacterium thermosaccharolyticum as an H2 producer are found. Discoloration of granular sludge from black to white and granule stability was observed in DF.

The generation of hydrogen-enriched synthesis gas from catalytic steam gasification of biomass with in-situ CO2 capture utilizing CaO has a high perspective as clean energy fuels. The present study focused on the process modeling of catalytic steam gasification of biomass using palm empty fruit bunch (EFB) as biomass for hydrogen generation through experimental work. Experiment work has been carried out using a fluidized bed gasifier on a bench-scale plant. The established model integrates the kinetics of EFB catalytic steam gasification reactions, in-situ capturing of CO2, mass and energy balance calculations. Chemical reaction constants have been calculated via the parameters fitting optimization approach. The influence of operating parameters, mainly temperature, steam to biomass, and sorbent to biomass ratio, was investigated for the hydrogen purity and yield through the experimental study and developed model. The results predicted approximately 75 vol% of the hydrogen purity in the product gas composition. The maximum H2 yield produced from the gasifier was 127 gH2/kg of EFB via experimental setup. The increase in both steam to biomass ratio and temperature enhanced the production of hydrogen gas. Comparing the results with already published literature showed that the current system enables to produce a high amount of hydrogen from EFB.

Syngas production from biomass gasification is a potentially sustainable and alternative means of conventional fuels. The current challenges for biomass gasification process are biomass storage and tar contamination in syngas. Co-gasification of two biomass and use of mineral catalysts as tar reformer in downdraft gasifier is addressed the issues. The optimized and parametric study of key parameters such as temperature, biomass blending ratio, and catalyst loading were made using Response Surface Methodology (RSM) and Artificial Neural Network (ANN) on tar reduction and syngas. The maximum H2 was produced when Portland cement used as catalyst at optimum conditions, temperature of 900 °C, catalyst-loading of 30%, and biomass blending-ratio of W52:OPF48. Higher CO was yielded from dolomite catalyst and lowest tar content obtained from limestone catalyst. Both RSM and ANN are satisfactory to validate and predict the response for each type of catalytic co-gasification of two biomass for clean syngas production.

The duration of photofermentative hydrogen production from sugar-based nutrients is limited by gradual acidification caused by the production of organic acids, leading to suboptimal pH. To address this issue, a custom pH control system was built and installed on a 20 L tubular photobioreactor, and operated under outdoor conditions. Long-term, single-stage hydrogen production from molasses was achieved using the purple non-sulfur bacterium, Rhodobacter capsulatus. The run lasted for 48 days, the longest duration achieved in a tubular photobioreactor on molasses as the only feed. pH was maintained close to its optimum value. High-purity hydrogen (above 90% by mole, on average) and near-complete conversion of sucrose was observed. The highest hydrogen productivity was 0.69 molH2/(m3.h). On the other hand, hydrogen production was observed to cease after periods of activity. Production resumed after dilution followed by artificial illumination, indicating that the production activity could be recovered during prolonged runs.

This study presents research results on electricity production from waste activated sludge using MFCs during stabilization process. Different MFC configurations equipped with various electrodes were used. Voltage measurements were continuously done during 35 days of MFC operation. Experimental results showed that bioelectricity generation was linked to volatile solids (VS) and protein reductions as a fraction of extracellular polymeric substances (EPS). Double chamber MFC reactor equipped with graphite electrodes had better power and current densities as 312.98 mW/m(2) and 39.07 mu A/cm(2) while single chamber MFC equipped with titanium electrodes revealed better power and current densities as 97.60 mW/m(2) and 17.63 mu A/cm(2), respectively. Molecular results indicated that power outputs of MFCs effected by diverse microbial communities in anode biofilms. Although organic matter degradation is reported as 35%-55% VS reduction for digesters, this research provided a promising approach for sludge stabilization with enhanced degrading of organic matters up to 75% by using MFCs. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Hydrogen production by biogas conversion represent a promising solution for reduction of fossil CO2 emissions. In this work, a detailed techno-economic analysis was performed for decarbonized hydrogen production based on biogas conversion using calcium and chemical looping cycles. All evaluated concepts generate 100,000 Nm3/h high purity hydrogen. As reference cases, the biogas steam reforming design without decarbonization and with CO2 capture by gas-liquid chemical absorption were also considered. The results show that iron-based chemical looping design has higher energy efficiency compared with the gas-liquid absorption case by 2.3 net percentage points as well as a superior carbon capture rate (99% vs. 65%). The calcium looping case shows a lower efficiency than chemical scrubbing, with about 2.5 net percentage points, but the carbon capture rate is higher (95% vs. 65%). The hydrogen production cost increases with decarbonization, the calcium looping shows the most favourable situation (37.14 €/MWh) compared to the non-capture steam reforming case (33 €/MWh) and MDEA and iron looping cases (about 42 €/MWh). The calcium looping case has the lowest CO2 avoidance cost (10 €/t) followed by iron looping (20 €/t) and MDEA (31 €/t) cases.

In the anaerobic biological treatment of pulp and papermaking wastewater, the gradual deposition of CaCO3 eventually leads to the inhibition of the activity of anaerobic granular sludge. In this study, a hydrogen production bacterial Raoultella DW01 was isolated from domesticated anaerobic granular sludge. The fermentation conditions were designed using central composite design, and the optimum conditions obtained by response surface analysis encompassed an initial pH 5.77, 4.13 g/L l -glutamic acid and an inoculation amount of 15%. The H2 production yield represented a 29.5% increase over the unoptimized conditions. Finally, the effect of adding DW01 on the biogas production in anaerobic granular sludge with different sludge ages was investigated. The cumulative biogas yield and the max biogas production rate increased by 27.8% and 53.5% after adding DW01 to a sludge with an age of 335 days compared with the on-intensified sludge. This paper provides a way to alleviate the CaCO3 deposition by intensifying the activity of H2 and acid-producing bacteria via improving the activity of granular sludge.

Water electrolysis produces HHO gas by using sodium hydroxide catalyst. Dry and wet cells designs are applied producing the gas flow rates at 0.5 and 0.75 LPM, respectively. Tests are done in a diesel engine at engine speed variation and full load. Performance, combustion characteristics and emissions investigations of diesel engines using HHO gas from dry and wet cells are performed. HHO gas addition enhances the brake thermal efficiency by 2 and 2.5% but the exhaust gas temperature highest decreases for dry and wet cells are 8 and 10%, respectively about diesel oil. The maximum decreases are evaluated as for CO (15, 22%), HC (31, 39%), NOx (35, 42%) and smoke emissions (25, 35%), respectively for dry and wet cells about diesel fuel. The improvements in cylinder pressures are 5 and 10%, respectively and the heat release rate enhancements are 4.5 and 6.5%, respectively about pure diesel for dry and wet configurations.