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An ionic liquid of N-methylmorpholine-N-oxide (NMMO) was used to effectively pretreat cassava residues for the efficient enzymatical hydrolysis and cogeneration of fermentative hydrogen and methane. The reducing sugar yield of enzymolysed cassava residues with NMMO pretreatment improved from 36 to 42g/100g cassava residues. Scanning electron microscopy images revealed the formation of deep grooves (∼4μm wide) and numerous pores in the cassava residues pretreated with NMMO. X-ray diffraction patterns showed that the crystallinity coefficient of NMMO-pretreated cassava residues decreased from 40 to 34. Fourier transform infrared spectra indicated that crystal cellulose I was partially transformed to amorphous cellulose II in the NMMO-pretreated cassava residues. This transformation resulted in a reduced crystallinity index from 0.85 to 0.77. Hydrogen yield from the enzymolysed cassava residues pretreated with NMMO increased from 92.3 to 126mL/gTVS, and the sequential methane yield correspondingly increased from 79.4 to 101.6mL/g TVS., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Aquatic micro-algae can be used as feedstocks for gaseous biofuel production via biological fermentation. However, micro-algae usually have low C/N ratios, which are not advantageous for fermentation. In this study, carbon-rich macro-algae (Laminaria digitata) mixed with nitrogen-rich micro-algae (Chlorella pyrenoidosa and Nannochloropsis oceanica) were used to maintain a suitable C/N ratio of 20 for a two-stage process combining hydrogen and methane fermentation. Co-fermentation of L. digitata and micro-algae facilitated hydrolysis and acidogenesis, resulting in hydrogen yields of 94.5-97.0mL/gVS; these values were 15.5-18.5% higher than mono-fermentation using L. digitata. Through the second stage of methane co-fermentation, a large portion of energy remaining in the hydrogenogenic effluents was recovered in the form of biomethane. The two-stage batch co-fermentation markedly increased the energy conversion efficiencies (ECEs) from 4.6-6.6% during the hydrogen fermentation to 57.0-70.9% in the combined hydrogen and methane production., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The hydrogenase genes (hoxEFUYH) of Synechocystis sp. PCC 6803 were cloned and heterologously expressed in Enterobacter aerogenes ATCC13408 for the first time in this study, and the hydrogen yield was significantly enhanced using the recombinant strain. A recombinant plasmid containing the gene in-frame with Glutathione-S-Transferase (GST) gene was transformed into E. aerogenes ATCC13408 to produce a GST-fusion protein. SDS-PAGE and western blot analysis confirm the successful expression of the hox genes. The hydrogenase activity of the recombinant strain is 237.6±9.3ml/(g-DW·h), which is 152% higher than the wild strain. The hydrogen yield of the recombinant strain is 298.3ml/g-glucose, which is 88% higher than the wild strain. During hydrogen fermentation, the recombinant strain produces more acetate and butyrate, but less ethanol. This is corresponding to the NADH metabolism in the cell due to the higher hydrogenase activity with the heterologous expression of hox genes., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Biofuels derived from biomass will play a major role in future renewable energy supplies in transport. Gaseous biofuels have superior energy balances, offer greater greenhouse gas emission reductions and produce lower pollutant emissions than liquid biofuels. Biogas derived through fermentation of wet organic substrates will play a major role in future transport systems. Biogas (which is composed of approximately 60% methane/hydrogen and 40% carbon dioxide) requires an upgrading process to reduce the carbon dioxide content to less than 3% before it is used as compressed gas in transport. This paper reviews recent developments in fermentative biogas production and upgrading as a transport fuel. Third generation gaseous biofuels may be generated using marine-based algae via two-stage fermentation, cogenerating hydrogen and methane. Alternative biological upgrading techniques, such as biological methanation and microalgal biogas upgrading, have the potential to simultaneously upgrade biogas, increase gaseous biofuel yield and reduce carbon dioxide emission., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Cassava ethanol wastewater (CEW) was subjected to sequential dark H2, photo H2 and CH4 fermentation to maximize H2 production and energy yield. A relatively low H2 yield of 23.6mL/g soluble chemical oxygen demand (CODs) was obtained in dark fermentation. To eliminate the inhibition of excessive NH4(+) on sequential photo fermentation, zeolite was used to remove NH4(+) in residual dark solution (86.5% removal efficiency). The treated solution from 5gCODs/L of CEW achieved the highest photo H2 yield of 369.7mL/gCODs, while the solution from 20gCODs/L gave the lowest yield of 259.6mL/gCODs. This can be explained that photo H2 yield was correlated to soluble metabolic products (SMPs) yield in dark fermentation, and specific SMPs yield decreased from 38.0 to 18.1mM/g CODs. The total energy yield significantly increased to 8.39kJ/gCODs by combining methanogenesis with a CH4 yield of 117.9mL/gCODs., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Ferric oxide nanoparticles (FONPs) were used to facilitate dark hydrogen fermentation using Enterobacter aerogenes. The hydrogen yield of glucose increased from 164.5±2.29 to 192.4±1.14mL/g when FONPs concentration increased from 0 to 200mg/L. SEM images of E. aerogenes demonstrated the existence of bacterial nanowire among cells, suggesting FONPs served as electron conduits to enhance electron transfer. TEM showed cellular internalization of FONPs, indicating hydrogenase synthesis and activity was potentially promoted due to the released iron element. When further increasing FONPs concentration to 400mg/L, the hydrogen yield of glucose decreased to 147.2±2.54mL/g. Soluble metabolic products revealed FONPs enhanced acetate pathway of hydrogen production, but weakened ethanol pathway. This shift of metabolic pathways allowed more nicotinamide adenine dinucleotide for reducing proton to hydrogen., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

To enhance biohydrogen production from glucose and xylose in the presence of aldehyde inhibitors, reducing agent (i.e., sodium borohydride) was in situ added for effective detoxification. The detoxification efficiencies of furfural (96.7%) and 5-hydroxymethylfurfural (5-HMF, 91.7%) with 30mM NaBH4 were much higher than those of vanillin (77.3%) and syringaldehyde (69.3%). Biohydrogen fermentation was completely inhibited without detoxification, probably because of the consumption of nicotinamide adenine dinucleotide (NADH) by inhibitors reduction (R-CHO+2NADH→R-CH2OH+2NAD(+)). Addition of 30mM NaBH4 provided the reducing power necessary for inhibitors reduction (4R-CHO+NaBH4+2H2O→4R-CH2OH+NaBO2). The recovered reducing power in fermentation resulted in 99.3% recovery of the hydrogen yield and 64.6% recovery of peak production rate. Metabolite production and carbon conversion after detoxification significantly increased to 63.7mM and 81.9%, respectively., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The inhibitory effects of furan derivatives [i.e. furfural and 5-hydroxymethylfurfural (5-HMF)] and phenolic compounds (i.e. vanillin and syringaldehyde) on dark hydrogen fermentation from glucose were comparatively evaluated. Phenolic compounds exhibited stronger inhibition on hydrogen production and glucose consumption than furan derivatives under the same 15mM concentration. Furan derivatives were completely degraded after 72h fermentation, while over 55% of phenolic compounds remained unconverted after 108h fermentation. The inhibition coefficients of vanillin (14.05) and syringaldehyde (11.21) were higher than those of 5-HMF (4.35) and furfural (0.64). Vanillin exhibited the maximum decrease of hydrogen yield (17%). The consumed reducing power by inhibitors reduction from R-CHO to RCH2OH was a possible reason contributed to the decreased hydrogen yield. Vanillin exhibited the maximum delay of peak times of hydrogen production rate and glucose consumption. Soluble metabolites and carbon conversion efficiency decreased with inhibitors addition, which were consistent with hydrogen production., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Microwave-heated alkali pretreatment (MAP) was investigated to improve enzymatic digestibility and H2/CH4 production from water hyacinth. SEM revealed that MAP deconstructed the lignocellulose matrix and swelled the surfaces of water hyacinth. XRD indicated that MAP decreased the crystallinity index from 16.0 to 13.0 because of cellulose amorphisation. FTIR indicated that MAP effectively destroyed the lignin structure and disrupted the crystalline cellulose to reduce crystallinity. The reducing sugar yield of 0.296 g/gTVS was achieved at optimal hydrolysis conditions (microwave temperature = 190°C, time = 10 min, and cellulase dosage = 5 wt%). The sequentially fermentative hydrogen and methane yields from water hyacinth with MAP and enzymatic hydrolysis were increased to 63.9 and 172.5 mL/gTVS, respectively. The energy conversion efficiency (40.0%) in the two-stage hydrogen and methane cogeneration was lower than that (49.5%) in the one-stage methane production (237.4 mL/gTVS) from water hyacinth with MAP and enzymatic hydrolysis., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The physicochemical properties of cassava residues subjected to microwave (or steam)-heated acid pretreatment (MHAP or SHAP) were comparatively investigated to improve fermentative hydrogen and methane cogeneration. The hydrogen yield from cassava residues with MHAP and enzymolysis was higher (106.2 mL/g TVS) than that with SHAP and enzymolysis (102.1 mL/g TVS), whereas the subsequent methane yields showed opposite results (75.4 and 93.2 mL/g TVS). Total energy conversion efficiency increased to 24.7%. Scanning electron microscopy images revealed MHAP generated numerous regular micropores (∼6 μm) and SHAP generated irregular fragments (∼23 μm) in the destroyed lignocellulose matrix. Transmission electron microscopy images showed SHAP generated wider cracks (∼0.2 μm) in delaminated cell walls than MHAP (∼0.1 μm). X-ray diffraction patterns indicated MHAP caused a higher crystallinity index (33.00) than SHAP (25.88), due to the deconstruction of amorphous cellulose. Fourier transform infrared spectroscopy indicated MHAP caused a higher crystallinity coefficient (1.20) than SHAP (1.12)., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The biological hydrogen production from amino acids obtained by protein degradation was comprehensively investigated to increase heating value conversion efficiency. The five amino acids (i.e., alanine, serine, aspartic acid, arginine, and leucine) produced limited hydrogen (0.2-16.2 mL/g) but abundant soluble metabolic products (40.1-84.0 mM) during dark-fermentation. The carbon conversion efficiencies of alanine (85.3%) and serine (94.1%) during dark-fermentation were significantly higher than those of other amino acids. Residual dark-fermentation solutions treated with zeolite for NH4(+) removal were inoculated with photosynthetic bacteria to further produce hydrogen during photo-fermentation. The hydrogen yields of alanine and serine through combined dark- and photo-fermentation were 418.6 and 270.2 mL/g, respectively. The heating value conversion efficiency of alanine to hydrogen was 25.1%, which was higher than that of serine (21.2%)., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The thermodynamic comparison in dark fermentation between amino acids and reducing sugars released from Nannochloropsis oceanica biomass are investigated for the first time. The total utilisation efficiencies of amino acids and reducing sugars are both about 95% in dark fermentation. But the consumption time of most amino acids is about 2 times as long as that of most reducing sugars in dark fermentation. A three-stage method comprising dark fermentation, photofermentation and methanogenesis is proposed to improve hydrogen and energy yields from N. oceanica biomass. Overall, the maximum hydrogen yield of 183.9 ml/g-total volatile solids (TVS) and the methane yield of 161.3 ml/g-TVS are achieved from N. oceanica biomass through the three-stage method. The total energy yield of hydrogen and methane from microalgae biomass through the three-stage method is 1.7 and 1.3 times higher than those through the two-stage (dark fermentation and methanogenesis) and single-stage (methanogenesis) methods, respectively., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Glutamic acid can hardly produce hydrogen via dark- or photo-fermentation without pretreatment. In this study, a novel process of acidogenic pretreatment with bacteria and zeolite treatment for NH4(+) removal was proposed to use glutamic acid as feedstock in photo-fermentation for efficient hydrogen production. Glutamic acid pretreated with acidogenic bacteria produces soluble metabolite products. After zeolite treatment, the acidulated solution, which mainly contains acetate, butyrate, and NH4(+), shows a decrease in NH4(+) concentration from 36.7mM to 3.2mM (NH4(+) removal efficiency of 91.1%). After NH4(+) removal, the treated solution is incubated with photosynthetic bacteria, exhibiting a maximum hydrogen yield of 292.9mL/g(-glutamic acid) during photo-fermentation. The residual solution from photo-fermentation is reused by methanogenic bacteria to produce a maximum methane yield of 102.7mL/g. The heating value conversion efficiency from glutamic acid to gas fuel significantly increases from 18.9% during photo-fermentation to 40.9% in the combined photo-fermentation and methanogenesis process., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Objective: We amplified and overexpressed the FHL activator (fh1A) in E. aerogenes ATCC13408 to enhance hydrogen production., Methods: By using universal primers and genome walking, we cloned the full open reading frame (ORF) of fh1A gene. We inserted it into the glutathion S-transferase (GST) fusion expression vector pGEX4T-2-Cat, and transformed the recombinant plasmid into E. aerogenes ATCC13408 via electroporation for expression. Then we measured the hydrogen production of the recombinant strain in a batch culture., Results: We found that the ORF of fh1A was 2073 base pair in length, potential to encode a 690 amino acid peptide (GenBank accession GU188474). The Fh1A protein from E. aerogenes ATCC13408 shared high amino acid identities with those from other bacterial species. By using SDS-PAGE and Western blot analysis, we confirmed that the fh1A gene had successfully expressed in the strain. The hydrogen yield of the recombinant strain was increased from 1.23 to 1.48 mol H2/mol glucose. [ Conclusion ] Enhancement of hydrogen productivity was attained under anaerobic conditions with the recombinant strain.

A two-phase anaerobic process to produce hydrogen and methane from potatoes was investigated. In the first phase, hydrogen was produced using heat-shocked sludge. About 12h lag-phase vanished, hydrogen yield increased from 200.4 ml/g-TVS to 217.5 ml/g-TVS and the maximum specific hydrogen production rate also increased from 703.4 ml/g-VSS d to 800.5 ml/g-VSS d when improved substrate was used, in which Cl(-) was substituted for SO(4)(2-). Better performances of 271.2 ml-H(2)/g-TVS and 944.7 ml-H(2)/g-VSS d were achieved when potatoes were pretreated by alpha amylase and glucoamylase. In the second phase, methane was produced from the residual of the first phase using methanogens. The maximum additional methane yield was 157.9 ml/g-TVS and the maximum specific methane production rate was 102.7 ml/g-VSS d. The results showed that the energy efficiency increased from about 20% (hydrogen production process) to about 60%, which indicated the energy efficiency can be improved by combined hydrogen and methane production process.

Biohydrogen production from straw by anaerobic fermentation of digested sludge was studied. The influence of the main parameters such as particle size, the ratio of substrate to cellulase, pretreatment method and pH on the straw fermentation was investigated. With NaOH pretreatment, the rice straw with average particle size of 170 tm was fermented after hydrolyzed by cellulase with the ratio of substrate to cellulase as 1:1. And its maximal velocity and the total volume of hydrogen are respectively 0.58 mL/(h x g) and 90.5 m/g.

In order to accelerate water dissociation kinetics and improve hydrogen evolution reaction (HER) in alkaline electrolyzer, pulse-activation engineering was proposed to induce lattice transformation of layered double hydroxides (LDHs) electrocatalysts. Physicochemical characterizations and density functional theory (DFT) calculations confirmed that FeOOH crystals diminished with a pulse potential of 1000 cycles (cls) in non-Faradaic region (−0.8∼0 V) and transformed into more stable CoFeLDH nanosheet arrays in Fe-rich system. The above transformation effectively reduced H∗ adsorption energy to accelerate water decomposition for efficient hydrogen evolution reaction. This was because pulse-activation accelerated electron transfer from Co2+ to Fe(3+δ)+ through intermittent input negative potential, reducing the high oxidation state of Fe(3+δ)+ in FeOOH to generate more stable CoFeLDH. The optimized pulse-activation with CoFeLDH electrocatalyst after 1000 cls decreased the overpotential of alkaline hydrogen evolution by 36%, from 225 mV to 144 mV at −10 mA cm−2. Schematic of pulse-activation engineering of CoFeLDH electrocatalyst for efficient alkaline hydrogen evolution. [Display omitted] • Pulse-activation engineering of LDH was proposed to promote HER. • FeOOH crystals transformed into CoFeLDH after pulse-activation in Fe-rich system. • Lattice transformation of CoFeLDH reduced the energy barrier of key steps. • The overpotential of CoFeLDH decreased from 225 mV to 144 mV after 1000 cls pulse-activation. [ABSTRACT FROM AUTHOR]

• The maximum explosion pressures and maximum rates of pressure rise of the ammonia-hydrogen-air mixture linearly increase as the initial pressure increases. • The explosion characteristic parameters vary monotonously as the equivalence ratio increases, and the peak value is obtained at the equivalence ratio of 1.1. • The improvement of the explosion intensity slightly reduces as the hydrogen concentration approaches 50%. • Hydrogen addition reinforces the explosion characteristics of the ammonia-air mixture by prominently improving the hydrodynamic instability and thermal-diffusion instability. Ammonia-hydrogen blended fuel has drawn substantial attention as an environmentally friendly, carbon-free fuel because it effectively overcomes the inherent disadvantages of pure ammonia in combustion performance, such as a high ignition energy, slow combustion rate, and low combustion efficiency. While recent research on the combustion performance of hydrogen-ammonia blends has advanced, there remains a scarcity of studies addressing the explosion characteristics of these fuels. In this paper, a series of experiments conducted within a standard 20-L spherical combustion chamber to investigate the explosion characteristics of ammonia-hydrogen-air premixed gases under diverse conditions, spanning from low to high pressures (0.02–0.3 MPa) and from fuel-lean to fuel-rich scenarios (0.7–1.5), are discussed. The results reveal that the explosion characteristics are pronouncedly enhanced by hydrogen addition. The maximum explosion pressure (P max) and maximum pressure rise rate ((d P /d t) max) increase, while the explosion time (t exp) decreases with increasing hydrogen concentration. P max and (d P /d t) max exhibit linear increases as the initial pressure rises and reach their peaks at an equivalence ratio of 1.1; t exp displays nonmonotonic variations with increasing initial pressure and equivalence ratio. Hydrogen addition remarkably increases the hydrodynamic instability and thermal-diffusion instability of the reactive mixture, enhances the thermal-mass diffusion on the flame front, and promotes flame deformation and cellular structure formation, resulting in an improvement of the flame propagation and compression effect on the unburnt reactant before the flame. Research into the explosion characteristics provides valuable insights for the safe storage and transportation of ammonia-hydrogen blended fuels. These results indicate avenues for further enhancing the detonation characteristics and explosion performance of ammonia-hydrogen blended fuels. [ABSTRACT FROM AUTHOR]

The spillover of hydrogen species and its role in tuning the activity and selectivity in catalytic hydrogenation have been investigated in situ using surface‐enhanced Raman spectroscopy (SERS) with 10 nm spatial resolution through the precise fabrication of Au/TiO2/Pt sandwich nanostructures. In situ SERS study reveals that hydrogen species can efficiently spillover at Pt‐TiO2‐Au interfaces, and the ultimate spillover distance on TiO2 is about 50 nm. Combining kinetic isotope experiments and density functional theory calculations, it is found that the hydrogen spillover proceeds via the water‐assisted cleavage and formation of surface hydrogen–oxygen bond. More importantly, the selectivity in the hydrogenation of the nitro or isocyanide group is manipulated by controlling the hydrogen spillover. This work provides molecular insights to deepen the understanding of hydrogen activation and boosts the design of active and selective catalysts for hydrogenation. [ABSTRACT FROM AUTHOR]

• Hydrothermal acid pretreatment strongly degraded algal bloom with tough cell walls. • Increasing acid concentration in pretreatment led to increased crystallinity index. • Hydrothermal acid (4% v/v) led to the highest H 2 yield and CH 4 yield. • Hydrothermal acid (8% v/v) led to a decrease in CH 4 yield due to Na+ inhibition. For the efficient utilization of algal biomass for gaseous biofuel production, hydrothermal acid pretreatment was employed in this study to hydrolyze algal bloom biomass harvested from Dianchi Lake in Yunnan Province of China. The hydrolyzed algal biomass was subjected to sequential dark hydrogen fermentation and anaerobic digestion to improve energy conversion efficiency (ECE). The results of X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy indicated that hydrothermal heating with increasing concentrations of sulfuric acid (H 2 SO 4 ; 0–8%) led to stronger damage to amorphous cellulose, which resulted in the increase in crystallinity index of cellulose. Hydrothermal heating with 4% H 2 SO 4 resulted in the maximum ECE of 55.7%, which yielded 37.33 mL H 2 /g-total volatile solids (TVS) and 261.93 mL CH 4 /g-TVS. However, the yields of hydrogen and methane were significantly reduced after hydrothermal pretreatment with 8% H 2 SO 4 which was most likely due to the substantial inhibitory effects on the bacteria and methanogens, caused by excess sodium ions introduced during pH adjustment process. [ABSTRACT FROM AUTHOR]

Abstract Algal blooms can be harvested as renewable biomass waste for gaseous biofuel production. However, the rigid cell structure of raw algae may hinder efficient microbial conversion for production of biohydrogen and biomethane. To improve the energy conversion efficiency, biomass from an algal bloom in Dianchi Lake was subjected to a hydrothermal/steam acid pretreatment prior to sequential dark hydrogen fermentation and anaerobic digestion. Results from X-ray diffraction and Fourier transform infrared spectroscopy suggest that hydrothermal acid pretreatment leads to stronger damage of the amorphous structure (including hemicellulose and amorphous cellulose) due to the acid pretreatment, as evidenced by the higher crystallinity index. Scanning electron microscopy analysis showed that smaller fragments (∼5 mm) and wider cell gaps (∼1 μm) on algal cell surfaces occurred after pretreatment. In comparison to steam acid pretreatment, hydrothermal acid pretreatment resulted in a maximum energy conversion efficiency of 44.1% as well as production of 24.96 mL H 2 /g total volatile solids (TVS) and 299.88 mL CH 4 /g TVS. Highlights • Algal bloom from Dianchi Lake was pretreated by hydrothermal/steam acid. • The microstructural changes before and after pretreatment were comparatively revealed. • Hydrothermal acid led to the highest H 2 yield (25.0 mL/g) and CH 4 yield (299.9 mL/g). • Hydrothermal acid led to the highest energy conversion efficiency of 44.1%. [ABSTRACT FROM AUTHOR]

Abstract Long-range extracellular electron transfer through microbial nanowires is critical for efficient bacterial behaviors. The application of carbon cloth on the dark hydrogen fermentation using transgenic Enterobacter aerogenes (E. aerogenes / HoxEFUYH) was first proposed to enhance hydrogen production from glucose. Scanning electron microscopy images showed that the microbial nanowires between E. aerogenes / HoxEFUYH cells almost vanished due to the presence of carbon cloth. Approximately 59.1% of microorganisms concentrated in biofilms on the surface of carbon cloth, which probably promoted the intercellular electron transfer. The results from Fourier transform infrared spectra and Excitation Emission Matrix spectra indicated that carbon cloth biofilms primarily included polysaccharide and protein. Moreover, the fluorophore of biofilms (88.1%) was much higher than that of supernatant (11.9%). The analysis of soluble metabolic degradation byproducts revealed that carbon cloth selectively enhanced the acetate pathway ( C 6 H 12 O 6 + 2 H 2 O → 2 C H 3 C O O H + 2 C O 2 + 4 H 2 ) , but weakened the ethanol pathway ( C 6 H 12 O 6 → 2 C 2 H 5 O H + 2 C O 2 ). With 1.0 g/L carbon cloth, the hydrogen yield increased by 26.6% to 242 mL/g, and the corresponding peak hydrogen production rate increased by 60.3%. Highlights • H 2 yield and production rate were enhanced with conductive carbon cloth. • Approximately 59.1% of the microorganisms concentrated in carbon cloth biofilms. • Biofilm soluble microbial products primarily included polysaccharide and protein. • Carbon cloth replaced nanowires between transgenic Enterobacter aerogenes cells. [ABSTRACT FROM AUTHOR]

Algae have emerged as a sustainable feedstock for gaseous biofuel production (such as hydrogen and methane). Fermentative sugars and amino acids can be obtained after suitable pretreatment and hydrolysis of algae. However, binary interactions between the carbonyl group ( C O) in sugars and the amino group ( NH 2 ) in amino acids possibly occur during thermal pretreatment, resulting in deficient hydrolysis and fermentation performance. In this study, algae-derived glucose and glycine as model substrates were subjected to thermochemical treatment (135 °C for 15 min) under neutral, acid and alkaline conditions to assess their decomposition routes and the associated implications on sequential biohydrogen and biomethane fermentation. Acid treatment mainly resulted in direct decomposition of glucose into 5-methylfurfural (C 6 H 6 O 2 , 34.4% of peak area). While thermal treatment with deionized water and alkaline led to the formation of nitrogen-containing Maillard compounds, namely 1-azido-4-dimethylaminobenzene (C 8 H 10 N 4 , 33.1%) and 2,3,5-trimethylpyrazine (C 7 H 10 N 2 , 49.0%), respectively. Untreated glucose/glycine yielded a biohydrogen production of 171.9 mL/g, while alkaline treatment exhibited a biohydrogen yield of only 5.9 mL/g due to the great loss of fermentable substrate. The total energy conversion efficiency (ECE) of 71.1% was achieved through the second-stage biomethane fermentation of untreated glucose/glycine. Comparatively, alkaline treatment significantly inhibited the total energy recovery with an ECE of 31.9%. The findings of this study suggested that optimised pretreatment strategy for algae needs to be developed to avoid fermentable compounds loss and achieve a higher ECE. [ABSTRACT FROM AUTHOR]

Pt nanoparticles supported on SBA-15 and amino-functionalized SBA-15 carriers with different Pt loadings were synthesized and characterized by BET, FTIR, XRD, HR-TEM and zeta potential towards the liquid phase catalytic reduction of bromate by hydrogen. The obtained results indicate that the catalytic reaction performance of Pt@NH 2 -SBA-15 solids was always significantly higher than that of Pt@SBA-15 for the same Pt loading due to the high zeta potential of NH 2 -SBA-15, which alludes to the ability of the amino-functionalization of SBA-15 to promote Pt catalyst activity for the reduction of aqueous bromate ions. [ABSTRACT FROM AUTHOR]

The growing amount of food waste (FW) in China poses great pressure on the environment. Complex solid organics limit the hydrolysis of FW, hence impairing anaerobic digestion. This study employed hydrothermal pretreatment (HTP) to facilitate the solubilization of FW. When HTP temperature increased from 100 to 200 °C, soluble carbohydrate content first increased to a peak at 140 °C and then decreased, whereas total carbohydrate content was negatively correlated with increasing temperature due to the enhanced degradation and Maillard reactions. Protein solubilization was dramatically promoted after HTP, whereas protein degradation was negligibly enhanced. The hydrogen and methane yields from hydrothermally pretreated FW under the optimum condition (140 °C, 20 min) through two-stage fermentation were 43.0 and 511.6 mL/g volatile solids, respectively, resulting in an energy conversion efficiency (ECE) of 78.6%. The ECE of pretreated FW was higher than that of untreated FW by 31.7%. [ABSTRACT FROM AUTHOR]

An integrated process involving cyanobacterium cultivation and three-stage fermentation was investigated to efficiently produce gaseous biofuels. The content and concentration of total carbohydrates in Arthrospira platensis biomass were remarkably enhanced through nutrient adjustments. Relative nitrogen starvation with continuous 15% (v/v) CO 2 bubbling led to the accumulation of large-molecular-weight glycogen as an intracellular energy reserve, whereas 0.5 mol/L NaCl addition at 3rd day resulted in the synthesis of small-molecular-weight carbohydrates (e.g., trehalose) as osmoprotectants. The total carbohydrates in A. platen sis cultivated under 15% (v/v) CO 2 and 0.5 mol/L NaCl stress occupied 53.4 wt% of the dried biomass. The harvested wet A. platensis biomass was pretreated with dilute acid and steam heating to give the maximum reducing sugar yield of 0.460 g/g volatile solids (VS). Scanning electron microscopy and transmission electron microscopy analyses revealed that the A. platensis cells were fractured section by section and thoroughly disrupted into small debris and fragments after pretreatment. A three-stage process combining dark hydrogen, photo hydrogen, and dark methane fermentation was employed for hydrogen and methane co-production using the pretreated A. platensis biomass. The hydrogen yield was 96 mL/gVS after first-stage dark fermentation, whereas the concentration of soluble metabolic products (SMPs) reached 9.692 g/L. Through the combined dark and photo hydrogen fermentation, the hydrogen yield significantly increased to 429 mL/gVS, corresponding to an SMP removal efficiency of 95.96%. The overall energy yield was boosted to 10.51 kJ/gVS after third-stage dark methane fermentation. [ABSTRACT FROM AUTHOR]

Water hyacinth pretreated with microwave-assisted dilute acid was used for fermentation to produce hydrogen using four kinds of genetically modified bacteria for the first time in this study. The genes of several hydrogenase were over-expressed in Enterobacter cloacae CICC10017 and Enterobacter aerogenes ATCC13408. Four recombinant strains including E. cloacae/HPP, E. aerogenes/HycE, E. aerogenes/HycG, and E. aerogenes/HoxEFUYH were obtained. Hydrogen yields from water hyacinth were investigated, which were enhanced using the recombinant strains. When water hyacinth was pretreated by microwave at 140°C for 15 min with 1% H2SO4 and then hydrolyzed by cellulase, the reducing sugar yield of 49.4 g/100 g hyacinth was 91.4% of the theoretical reducing sugar yield. Among the four genetically modified bacteria, E. cloacae/HPP gave the highest hydrogen yield of 74.9 mL/g- total volatile solids, which was 50% higher than that given by the wild strain from pretreated water hyacinth. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1296-1300, 2017 [ABSTRACT FROM AUTHOR]

Nuclear irradiation was used for the first time to generate efficient mutants of hydrogen-producing bacteria Enterobacter aerogenes , which were screened with larger colour circles of more fermentative acid by-products. E. aerogenes cells were mutated by nuclear irradiation of 60 Co γ-rays. The screened E. aerogenes ZJU1 mutant with larger colour circles enhanced the hydrogenase activity from 89.8 of the wild strain to 157.4 mL H 2 /(g DW h). The hereditary stability of the E. aerogenes ZJU1 mutant was certified after over ten generations of cultivation. The hydrogen yield of 301 mL H 2 /g glucose with the mutant was higher by 81.8% than that of 166 mL/g glucose with the wild strain. The peak hydrogen production rate of 27.2 mL/(L·h) with the mutant was higher by 40.9% compared with that of 19.3 mL/(L·h) with the wild strain. The mutant produced more acetate and butyrate but less ethanol compared with the wild strain during hydrogen fermentation. [ABSTRACT FROM AUTHOR]

The exotic species Spartina anglica spread in coastal beaches of China was first used as a potential biomass resource to co-produce hydrogen and methane through dark fermentation. S. anglica was subjected to four pretreatments, including alkali-assisted microwave heating (MH), alkali-assisted steam heating (SH), acid-assisted MH, and acid-assisted SH. Scanning electron micrographs revealed that acid-assisted SH disrupted S. anglica more thoroughly, resulting in the generation of smaller fragments and debris (5–30 μm). The acid-assisted SH pretreated S. anglica biomass with enzymolysis exhibited the highest reducing sugar yield of 0.743 g/g-volatile solids (VS), corresponding to a saccharification efficiency of 98.96%. The fermentative hydrogen yield from pretreated S. anglica was 135.9 mL/g-VS and the acetate and butyrate comprised 92.5% of the soluble metabolic products. Subsequent methane yield from the hydrogenogenic effluent reached up to 268.5 mL/g-VS. The energy conversion efficiency of S. anglica dramatically increased from 9.9% in fermentative hydrogen production to 74.9% in fermentative hydrogen and methane co-production. [ABSTRACT FROM AUTHOR]

Physicochemical characterization of typical municipal solid wastes were used for fermentative hydrogen and methane co-production in this study. Scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction analyses were used to characterize the physicochemical properties of food waste (FW) and sewage sludge (SS). FTIR spectra revealed that FW had stronger characteristic peaks of carbohydrates, proteins, and lipids, whereas SS had a higher characteristic peak of mineral compounds. Fermentative hydrogen production was then applied to strengthen acidogenesis to increase methane production rate through anaerobic digestion. The maximum methane production rates from FW and SS (13.31 and 7.18 mL/g-VS/d) in the two-stage process were 14.8% and 15.1% higher than those in the one-stage process, respectively. The peak times of methane production from FW and SS in the two-stage process were 6 and 3 days earlier than those in the one-stage process, respectively. The energy recovery efficiencies of FW and SS in the two-stage process were 3.3–8.7% higher than those in the one-stage process. [ABSTRACT FROM AUTHOR]

Hydrogen is considered as an ideal alternative to fossil fuels due to its high energy density by mass and clean combustion product. Using anaerobic bacteria to ferment biomass and produce renewable hydrogen is receiving increased attention. Aquatic algal biomass, which can be sourced from natural algal bloom or mass cultivation, is considered as a promising substrate for hydrogen fermentation. This paper reviews the recent developments in fermentative hydrogen production from algal biomass, with the main focus on hydrogen production potential and its current technological state. The stoichiometric hydrogen yields of algal biomass in dark fermentation are predicted based on the theoretical contents of monosaccharides from carbohydrates and glycerol from lipids in biomass. Hydrogen yields of algal biomass by dark fermentation can be improved by using efficient pretreatments at optimized biomass carbon/nitrogen ratios with domesticated hydrogen-producing bacteria as the inoculum. The effluent of dark fermentation, which is rich in volatile fatty acids, should be used for the production of biofuels and biochemicals to further improve the energy efficiency and economic feasibility of hydrogen fermentation. [ABSTRACT FROM AUTHOR]

To improve fermentative hydrogen production from water hyacinth pretreated with microwave-assisted dilute H 2 SO 4 and cellulase, activated carbon (AC) was used to effectively remove fermentative inhibitors in hydrolysates. The removal efficiencies of vanillin, 5-hydroxymethyl furfural and furfural in artificial hydrolysates of water hyacinth were 84.8%, 45.4%, and 39.5%, respectively. The glucose content in the hydrolysates decreased by 13.8% with AC treatment. The hydrolysates of water hyacinth were used to domesticate hydrogen producing bacteria (HPB) and improve their adaptability. The hydrogen yield from the hydrolyzed water hyacinth with AC detoxification and HPB domestication increased from 104.0 to 134.9 mL/g total volatile solids (TVS). The sequential methane yield (107.7 mL/g TVS) significantly increased the energy conversion efficiency from 8.5% to 30.9%. [ABSTRACT FROM AUTHOR]

Fermentative hydrogen production from biomass wastes is a promising technology combining waste treatment and clean fuel production. Biomass wastes have various types and components, while the fundamental fermentation reactions involve monosaccharides and amino acids. In this study, typical monosaccharides (glucose and xylose) and amino acids (glutamic acid, aspartic acid, serine, glycine, arginine and alanine) were mixed and fermented by anaerobic fermentative bacteria (AFB) obtained from heat pre-treated anaerobic digestion sludge, to directly examine the substrate consumption and hydrogen production during the co-fermentation of monosaccharides and amino acids. Hydrogen was mainly produced from the fermentation of monosaccharides, but not from the fermentation of amino acids. Monosaccharide consumption generally preceded amino acid consumption. Glucose was more readily utilised by AFB than xylose. The maximum volumetric hydrogen productivity and production rate from the co-fermentation of glucose and mixed amino acids was 2.7 times and 3.1 times higher than those from the co-fermentation of xylose and mixed amino acids. Glutamic acid, serine and alanine were more readily utilised by AFB than aspartic acid, glycine and arginine. The co-fermentation of monosaccharides and amino acids showed efficient energy conversion and carbon conversion, with the maximum efficiencies of 83.3% and 93.3%, respectively. [ABSTRACT FROM AUTHOR]

In order to efficiently utilize the biomass waste of algae bloom in Taihu Lake, China and improve energy conversion efficiency, a three-stage process comprising dark hydrogen fermentation with acid-domesticated hydrogenogens, photohydrogen fermentation, and methanogenesis was undertaken. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses showed that algal cells pretreated by microwave heating with diluted acid were degraded into smaller fragments (<5 μm) than those pretreated by steam heating with diluted acid. The microwave pretreatment of algae resulted in higher saccharification efficiency. The domesticated hydrogenogens in presence of acids improved the dark hydrogen production from microwave-pretreated algae biomass and led to a total combined dark and photofermentation hydrogen yield of 283.4 mL/g-total volatile solid (TVS). The energy conversion efficiency of steam-pretreated algae biomass remarkably increased to 47.0% by cogenerating 256.7 mL/g-TVS hydrogen and 253.5 mL/g-TVS methane in the three-stage process: dark-fermentation, photofermentation, and methanogenesis. [ABSTRACT FROM AUTHOR]

Abstract: 16s rRNA gene sequence analysis is applied in the semi-continuous fermentation of Chlorella pyrenoidosa to monitor changes in the microbial community of HPB (hydrogen-producing bacteria). The microbial community of HPB on the 4th day is mainly composed of one genus (Clostridium) including one primary species (Clostridium butyricum). The microbial community of HPB on the 22nd day is mainly composed of three genera (Clostridium, Sporanaerobacter and Eubacterium) including three primary species (Clostridium acetireducens, Clostridium cochlearium and Sporanaerobacter acetigenes). Fermentation results show that production of hydrogen and soluble metabolites by the simple microbial community is unstable with fluctuating pH values at earlier stages (days 1–4). By contrast, the production of hydrogen (51.7–62.0 mL/g-total volatile solids) and soluble metabolites (acetate/butyrate: 0.4–0.5 mol/mol) by complex microbial communities is fairly stable with a steady pH value of approximately 5.9 at later stages of fermentation (days 11–22). [Copyright &y& Elsevier]

Highlights: [•] Saccharification of C. pyrenoidosa is promoted by steam heating with diluted acid. [•] Dark H2 production is remarkably enhanced by using hydrolyzed biomass as feedstock. [•] H2 yield is dramatically increased by the combined dark and photo fermentation. [•] Energy conversion efficiency is markedly improved via co-generation of H2 and CH4. [Copyright &y& Elsevier]

Trehalose was pretreated by microwave heating with dilute acid to improve glucose yield and hydrogen production during dark-fermentation. An optimal glucose yield of 0.95 ± 0.08 g/g-trehalose was obtained when trehalose was pretreated by microwave heating with 1% dilute H2SO4 for 25 min at 120 °C. The hydrolyzed trehalose was inoculated with HPB (hydrogen-producing bacteria) to produce hydrogen during dark-fermentation. The residual solution of dark-fermentation was reused by PSB (photosynthetic bacteria) during photo-fermentation. The residual solution of photo-fermentation was reused by MPB (methane-producing bacteria) during methanogenesis. The maximum yields of hydrogen and methane were 731.3 ± 33.6 ml/g-trehalose and 116.9 ± 4.3 ml/g-trehalose. The sequential generation of hydrogen and methane from trehalose remarkably enhanced the energy conversion efficiency from 47.2 ± 2.2% in hydrogen fermentation to 72.2 ± 3.1% in combined hydrogen fermentation and methanogenesis. [ABSTRACT FROM AUTHOR]

Abstract: The sequential generation of hydrogen and methane from xylose by two-stage anaerobic fermentation was investigated for the first time in this study. The effects of substrate concentration, bacteria domestication and nitrogen source on hydrogen yield were studied in the first stage. The genetic characterization of the 16S rDNA was used to analyze the flora of strains domesticated with xylose and glucose. The maximum hydrogen yield is 190.6 ml H2/g xylose when the xylose feedstock concentration is 1% (w/v), hydrogenogens are domesticated with xylose and yeast extract is used as nitrogen source. The soluble metabolite byproducts (SMB) from the hydrogen-producing stage were reutilized by methanogens to produce methane in the second stage. Over 98 wt % of acetate and butyrate in the SMB are reutilized to give a methane yield of 216.5 ml CH4/g xylose. The sequential generation of hydrogen and methane from xylose markedly increases the energy conversion efficiency to 67.5%. [Copyright &y& Elsevier]

Abstract: The energy conversion efficiency in hydrogen and methane cogeneration from Arthrospira maxima biomass by two-phase fermentation is improved with bacteria domestication and enzymatic hydrolysis. The A. maxima biomass (dried weight) can theoretically cogenerate hydrogen and methane yields of 318 ml/g and 262 ml/g, which dramatically increases the theoretical energy conversion efficiency from 16.6% in hydrogen only production to 61.9%. The experimental hydrogen yield is increased from 49.7 ml/g to 64.3 ml/g, when the hydrogenogens community is domesticated with A. maxima biomass as carbon source. The hydrogen yield is further increased to 78.7 ml/g when A. maxima biomass is hydrolyzed with glucoamylase, which gives an energy conversion efficiency of 4.1% in hydrogen only production. The soluble metabolite byproducts from the first hydrogen-producing phase are reutilized by methanogens to produce methane of 109.5–145.5 ml/g in the second phase. The cogeneration of hydrogen and methane from A. maxima biomass markedly increases the experimental energy conversion efficiency to 27.7%. [Copyright &y& Elsevier]

Abstract: A novel reaction mechanism of H2 and CH4 cogeneration from water hyacinth (Eichhornia crassipes) was originally proposed to increase the energy conversion efficiency. The glucose and xylose hydrolysates derived from cellulose and hemicellulose are fermented to cogenerate H2 and CH4 by two-step anaerobic fermentation. The total volatile solid of hyacinth leaves can theoretically cogenerate H2 and CH4 yields of 303ml-H2/g-TVS and 211ml-CH4/g-TVS, which dramatically increases the theoretical energy conversion efficiency from 19.1% in only H2 production to 63.1%. When hyacinth leaves are pretreated with 3wt% NaOH and cellulase in experiments, the cogeneration of H2 (51.7ml-H2/g-TVS) and CH4 (143.4ml-CH4/g-TVS) markedly increases the energy conversion efficiency from 3.3% in only H2 production to 33.2%. Hyacinth leaves, which have the most cellulose and hemicellulose and the least lignin and ash, give the highest H2 and CH4 yields, while hyacinth roots, which have the most ash and the least cellulose and hemicellulose, give the lowest H2 and CH4 yields. [Copyright &y& Elsevier]

Abstract: In order to reutilize the residual solutions derived from hydrogen production and increase the energy conversion efficiency, a novel process of cogenerating hydrogen and methane from glucose using a two-phase anaerobic fermentation process was proposed and investigated. The effects of substrate concentration, weight ratio of inoculation to substrate, pH value and nutrient medium on hydrogen production were studied. The maximum specific hydrogen yield is 2.75molH2/molglucose when the initial glucose concentration is 1%, the weight ratio of inoculation to substrate is 2:1 and the pH value is 6. The residual solutions derived from hydrogen production were reused to produce methane by methanogen in another reactor. The maximum specific methane yield is 2.13molCH4/molglucose when the reutilization rates of ethanol, acetic acid, butyric acid, valeric acid, and caproic acid are all above 90%. The cogeneration process can dramatically increase the energy conversion efficiency from 23% (hydrogen only production) to 82%. [Copyright &y& Elsevier]

Low hydrogen dielectric film deposition method was used in PECVD. The properties of amorphous IGZO (a-IGZO) bottom-gate thin film transistor using this method were investigated and compared. The PBTS (Positive Bias Temperature Stress) and NBTS (Negative Bias Temperature Stress) reduced to 0.481V, and -0.269V, respectively. The overall properties of a-IGZO TFT using low hydrogen dielectric recipe meet the demand of oxide backplane in both LCD and OLED field. [ABSTRACT FROM AUTHOR]

Bimetallic phosphides as the cocatalysts have been demonstrated promising potential for boosting photocatalytic water splitting to produce hydrogen. Herein, a nickle-cobalt bimetallic phosphide (NiCoP) cocatalyst with flower-like structure built with nanoflakes in different directions is synthesized and self-assembled with protonated g-C 3 N 4 (HCN) nanosheets through electrostatic interaction. The resultant NiCoP/HCN is employed for photocatalytic hydrogen evolution reaction. Benefiting from the excellent metallic conductivity and unique flower-like structure of NiCoP that offers abundant active sites, the NiCoP/HCN exhibits highly efficient separation of the photo-generated charges and greatly improved hydrogen evolution activity. The H 2 evolution rate of the optimized NiCoP/HCN can reach 7951 μmol g−1 h−1, much higher than that of HCN nanosheets. The great potential of NiCoP for improving photocatalytic H 2 evolution of g-C 3 N 4 lights a valuable direction for exploring low cost and highly efficient non-noble metal cocatalysts for enhanced photocatalytic H 2 evolution. Flower-like NiCoP/protonated g-C 3 N 4 (HCN) photocatalyst was constructed and exhibited superior photocatalytic water splitting activity due to excellent metallic conductivity and unique flower-like structure of NiCoP. [Display omitted] • Flower-like NiCoP/protonated g-C 3 N 4 (HCN) photocatalyst was constructed. • NiCoP/HCN exhibits the superior photocatalytic water splitting activity. • Unique flower-like structure of NiCoP provides more active sites for H 2 production. • Excellent metallic conductivity of NiCoP facilitates efficient separation of the photogenerated charges. [ABSTRACT FROM AUTHOR]

A two-stage continuous fermentative hydrogen and methane co-production using macro-algae ( Laminaria digitata ) and micro-algae ( Arthrospira platensis ) at a C/N ratio of 20 was established. The hydraulic retention time (HRT) of first-stage H 2 reactor was 4 days. The highest specific hydrogen yield of 55.3 mL/g volatile solids (VS) was obtained at an organic loading rate (OLR) of 6.0 gVS/L/d. In the second-stage CH 4 reactor at a short HRT of 12 days, a specific methane yield of 245.0 mL/gVS was achieved at a corresponding OLR of 2.0 gVS/L/d. At these loading rates, the two-stage continuous system offered process stability and effected an energy yield of 9.4 kJ/gVS, equivalent to 77.7% of that in an idealised batch system. However, further increases in OLR led to reduced hydrogen and methane yields in both reactors. The process was compared to a one-stage anaerobic co-digestion of algal mixtures at an HRT of 16 days. A remarkably high salinity level of 13.3 g/kg was recorded and volatile fatty acid accumulations were encountered in the one-stage CH 4 reactor. The two-stage system offered better performances in both energy return and process stability. The gross energy potential of the advanced gaseous biofuels from this algal mixture may reach 213 GJ/ha/yr. [ABSTRACT FROM AUTHOR]

• Coal particles with different reaction depths are obtained by temperature control. • Further oxidation of the carbonyl group is the controlling step of CAWE. • The C-O structure of the surface layer of coal has highest oxidation activity. • The oxidation of coal particles mainly occurs on the external surface and pores. Coal-assisted water electrolysis can be used to produce pure hydrogen under mild conditions and reduce the electricity consumption required for water electrolysis by 40–60% while achieving clean utilization of coal. However, the kinetics for the process are very slow, and the mechanism has not yet been fully understood. Investigation of the oxidation mechanism for coal particles in the electrolysis process can help to clarify the control steps for the entire oxidation process so that research can be conducted in a more focused manner. In this study, coal particles were subjected to electrolysis with different extents of reaction using different reaction temperatures, and various analytical characterization methods, such as 13C NMR, were used to study the trends for multiple characteristic structures of coal molecules during the electrolysis process. The results show that the oxidation of coal particles mainly occurs on the external surface and pores, and its temperature coefficient is higher than that for Fe2+. Upon increasing the reaction temperature to 90 ℃, the reaction time can be reduced by more than half compared to room temperature. Aliphatic carbons, especially methylene-related structures, are the main oxidation sites in coal molecules, while aromatic carbons produce less oxidation. The oxidation rate for the C-O structure is faster, especially at the surface layer of coal molecules, and its content decreases gradually with increasing oxidation depth, while the oxidation rate for C = O and COOH is slower, which represents the main control step for the entire process of coal oxidation. [ABSTRACT FROM AUTHOR]

Carbon-assisted water electrolysis can significantly reduce the electricity consumption of electrolytic hydrogen production, but its slow kinetics limit its further development. In-depth investigation of the oxidation pathways and control steps of coal particles during electrolysis can help to improve the reaction rate in a more targeted manner. In this study, the electrochemical activities of several different ranks of coal, activated carbon, and graphite are compared, and the electrooxidation process is disentangled to investigate the kinetic characteristics of the oxidation of solution catalysts, the reaction of coal with solution catalysts and the electrooxidation of coal. Structural characterization is used to investigate the key factors affecting the electrochemical activity. The results show that coal particles mainly undergo indirect oxidation during electrolysis, and direct oxidation only accounts for a small fraction of oxidation; the oxidation of the solution catalyst on the electrode surface is reversible, and the controlling step in the whole process is the redox reaction between the solution catalyst and coal particles. A variety of oxygen-containing functional groups are generated on the surface of coal particles after electrolysis, among which the C-O group plays a more critical role in the oxidation activity. • For the first time, the kinetics of CAWE was studied in detail by splitting. • Direct evidence that coal particles mainly undergo indirect oxidation was obtained. • The oxidation of coal particles clearly has two phases. • The accuracy of Fe2+ concentration detection in flat electrodes is relatively high. [ABSTRACT FROM AUTHOR]

The study examined the thermal-deformation behavior of an MoNbHfZrTi refractory high-entropy alloy (RHEA), which were hydrogenated using a liquid hydrogenation method and then subjected to high-temperature uniaxial compression in the deformation temperature range of 1100–1250 °C and strain rate range of 0.5–10−3 s−1. Test results showed that: (1) When the deformation temperature was between 1100 and 1250 °C, hydrogen addition led to increased high-temperature peak stress of the alloy at higher strain rates of 0.5 and 10−1 s−1. At a low strain rate of ∼10−2 s−1, the addition of hydrogen causes a decrease in the high-temperature peak stress. However, at a lower strain rate of ∼10−3 s−1, hydrogen addition has insignificant effects on the high-temperature peak stress. (2) At a higher strain rate of ∼0.5 s−1, the major reasons for hydrogen-induced hardening of the peak stress were solution strengthening and dislocation pinning. (3) At a low strain rate of 10−2 s−1, the reason for decrease of the peak stress was that the hydrogen addition promoted the formation of precipitated phases, thereby facilitating dynamic recrystallization (DRX), and making the microstructure more uniform at high temperatures. • A new strategy called liquid hydrogenation was applied to RHEAs. • Hydrogen-induced hardening were found during thermal deformation. • Hydrogen accelerates dynamic recrystallization during thermal deformation. [ABSTRACT FROM AUTHOR]