Highest Hydrogen Production Rate Research Articles

Distinct Pathways Determined by Photocatalytic C─H or O─H Bond Activation for Hydroxyl Compounds Conversion Paired With Hydrogen Production

AbstractSelective control of C─H or O─H bond activation in photocatalytic conversion coupled with hydrogen production is a promising yet challenging goal. Here, an efficient photocatalytic system is reported that can produce high‐valued tartaric acid or formaldehyde and simultaneous producing hydrogen. At optimized conditions, the directional conversion of glycolic acid into tartaric acid is achieved with a selectivity of 76.24%, and the selectivity of methanol oxidation into formaldehyde reaches 88.21%. A high hydrogen production rate of 21.43 mmol·g−1·h−1 is obtained using glycolic acid as substrate. Mechanism studies reveal that α‐C─H bond is preferentially activated in glycolic acid adsorbed on the photocatalyst, while O─H bond is preferentially activated in methanol, forming carbon‐centered radical (•CH(OH)COOH) or oxygen‐centered radical (CH3O•) for subsequent coupling or oxidation reactions. This work demonstrates the selective control of the photocatalytic conversion process of different hydroxyl compounds, providing a new perspective for achieving organic compounds selective activation coupled with hydrogen production.

Interfacial Acid‐Like Microenvironment and Orbital Modulating Strategy toward Efficient Hydrogen Evolution in Neutral High‐Salinity Wastewater/Seawater

Electrochemical high‐salinity wastewater splitting is a promising technology for green hydrogen (H2) production. However, the kinetics of hydrogen evolution reaction (HER) in neutral media is slow, and the high theoretical potential of oxygen evolution reaction leads to large energy losses. Herein, an iron‐based electrocoagulation‐coupled hydrogen production integrated system (IEHPS) is constructed, which is realized by coupling low‐potential anodic iron oxidation reaction with cathodic HER. The non‐noble metal HxWO3‐Ni catalyst is synthesized by fabricating a proton sponge HxWO3 to achieve an interfacial acid‐like microenvironment and doping it with Ni heteroatom to modulate the 4d orbital of W, thereby weakening the adsorption strength of the W site toward hydrogen. Consequently, the HxWO3 Ni demonstrates remarkable performance characteristics, boasting a mere 131 mV overpotential at 10 mA cm−2 and Tafel slope of 44 mV dec− in neutral media. Operating at an applied voltage of 1.5 V, the IEHPS exhibits a high hydrogen production rate of 235 mL g−1 min−1 in seawater. It achieves nearly complete removal of contaminants like rhodamine B and heavy metal ions within a rapid 8–20 min, with an energy consumption of only 3.7 kWh Nm−3. This study provides a promising pathway for efficient and energy‐saving production of high‐purity hydrogen and effective treatment of high‐salinity wastewater.

Bioaugmentation with Clostridium pasteurianum for high-yield continuous bio-hydrogen production in a dynamic membrane bioreactor

This study demonstrated the feasibility of achieving high-yield continuous bio-H2 production through bioaugmentation with Clostridium pasteurianum. C. pasteurianum was introduced during the initial granulation stage in a dynamic membrane bioreactor (DMBR) inoculated with heat-treated digester sludge. Following bioaugmentation, the average hydrogen yield (HY) reached 3.07 ± 0.13 mol H2/mol hexoseconsumed, with a hydraulic retention time (HRT) of 2 h. This high-yield and high-rate hydrogen production performance was achieved alongside a high concentration of suspended and granular biomass as 21.02 ± 1.01 g VSS/L. The DM played a crucial role in prolonging the solid retention time of the suspended biomass to 12.15 h. C. pasteurianum emerged as the predominant species, constituting 92.3 % of the total bacterial population. This dominance significantly contributed to achieving the high HY, reaching 77 % of the theoretical maximum HY (4 mol H2/mol hexoseconsumed) by shifting the metabolic pathway from non-H2 production pathways to hydrogen-producing acetate. However, during further continuous operation, the hydrogen production pathway was gradually shifted towards the butyrate pathway, resulting in a decreased HY of 2.26 mol H2/mol hexoseconsumed along with the decreased population of C. pasteurianum. Additional bioaugmentation of C. pasteurianum during the maturational granulation stage did not impact the metabolic pathways or microbiome significantly, as the added strain was supposed to be washed out. This study provides insights into achieving high-yield continuous bio-H2 production through bioaugmentation with C. pasteurianum during the initial granulation stage. Further studies are necessary to sustain C. pasteurianum-dominated high HY with the acetate pathway during prolonged operation.

Cu-doped ZnCdS-based photocatalyst for efficient photocatalytic hydrogen production by photothermal assistance

In solar energy utilization, photocatalytic hydrogen production has been widely researched. To address issues such as low efficiency of photocatalysts, Cu-doped Zn0.5Cd0.5S composite photocatalysts were prepared using a hydrothermal method for photocatalytic hydrogen production. The Cu/Zn0.5Cd0.5S photocatalyst was characterized using XRD, XPS, SEM, TEM, UV–vis-DRS, fluorescence spectrophotometer, and electrochemical workstation. The results indicate that Cu doping alters the crystal and band structures of Zn0.5Cd0.5S. Hydrogen production experiments were conducted under xenon lamp irradiation, and at 45 °C, the highest hydrogen production rate was 2.72 and 1.63 times that of single Zn0.5Cd0.5S and Cu-doped Zn0.5Cd0.5S at room temperature (25 °C), respectively. Cu doping imparted a photothermal effect to the photocatalytic hydrogen production experiment, enhancing its efficiency.Cu doping captured electrons by replacing some Zn, constructing an internal electric field, forming defect energy levels, which hindered electron-hole recombination. Additionally, Cu ions acted as a plasma, inducing a plasma effect during hydrogen production, accelerating the rate of solar energy conversion to thermal energy, thus improving hydrogen production efficiency. This research not only provides a photocatalyst for photocatalytic hydrogen production but also utilizes it for photothermal synergistic catalysis.

Advanced Nanostructured Textile Catalysts for Enhanced Hydrogen Production in PEM Water Electrolysis: An Overview and Recent Developments

As the global focus shifts towards a zero-emission society, hydrogen has emerged as a critical element in various industries, particularly in green hydrogen production. A promising method for this is Polymer Electrolyte Membrane Water Electrolysis (PEMWE), which uses pure water and electricity to produce high-purity hydrogen. However, the efficiency of PEMWE is highly dependent on the effectiveness of its catalysts, particularly in the context of the catalyst-coated membranes (CCMs) employed in these systems. Conventional preparation of these CCMs involves multiple steps, including synthesis and application of a catalyst ink, which often leads to catalyst agglomeration and requires high Ir (Iridium) loadings to maintain uniformity and performance.In our latest study, we have developed a novel approach using ultralight conductive IrO2 nanostructured textiles (NST) as a catalyst layer for PEMWE. This innovative method successfully circumvents the issue of electrically isolated inactive catalysts, a common problem with lower Ir amounts in traditional catalyst layers. By employing a process of sputtering IrO2 onto water-soluble polymer nanofibers, we have achieved facile CCM preparation and demonstrated unprecedented long-term hydrogen evolution with ultra-low Ir mass loadings at high rates. Our study revealed that the high performance of these CCMs is derived from their low resistivity and unique porous three-dimensional structure.The preparation of NST involves dissolving polyvinylpyrrolidone (PVP) in methanol, followed by electrospinning this solution onto a metal-foil collector. The resulting PVP nanofibers then undergo a sputtering process to deposit IrO2, forming the nanostructured textiles. This method eliminates the need for wet chemical routes and labor-intensive processes typically associated with conventional catalyst layer preparations, thus offering a more environmentally friendly and scalable alternative.Our performance evaluations of these NST CCMs, with varying Ir mass loadings, have shown significant advancements. The operational cell voltages of CCMs containing as little as 0.05 mg-Ir cm−2 were suppressed across all investigated current densities compared to conventional CCMs. Notably, operational voltages remained below 2 V even at the highest current density of 7 A cm−2. This level of performance is unprecedented for CCMs with such low catalyst amounts. Additionally, the long-term stability of these CCMs was remarkable, with operational times exceeding 1500 hours without significant increases in voltage, showcasing their potential for practical applications.An essential aspect of our study was the analysis of the electrical properties and the surface structure of the IrO2 NSTs. We observed that the electrical conductivity of these textiles was significantly higher than that of conventional catalyst layers. This high conductivity, coupled with the unique interconnected structure of the textiles, ensures efficient electrical contact between nano catalysts and the current collector, thus avoiding the formation of isolated catalysts. Our analyses revealed that the IrO2 NSTs have unique surface terminations and a high number of undercoordinated surface Ir atoms, contributing to their high intrinsic catalytic activity.Further insights were gained through operando X-ray absorption spectroscopy (XAS) measurements, which showed that the IrO2-nanostructured textiles possess a large number of D-band holes and are intrinsically highly active. This finding is crucial as it links the unique chemical state of the textiles to their high activity in oxygen evolution reactions (OER), a key process in PEMWE.Our recent developments in nanostructured textile catalysts for PEMWE mark a significant leap in hydrogen production technology. By demonstrating high-rate hydrogen production at low operational voltages and with significantly lower Ir mass loadings compared to conventional CCMs, we have addressed major challenges in the field. These advancements not only enhance the efficiency and sustainability of hydrogen production but also open avenues for applying this technology to other electrochemical conversion cells, paving the way for broader applications and further research. In this talk, we discuss the latest activity on NST, and highlight the challenges and opportunities for hydrogen production.

Evaluation of different operational conditions in a microbial electrolysis cell inoculated with a pure culture of Shewanella oneidensis for hydrogen production.

Hydrogen is a promising alternative to meet the world's energy demand in the future because of its energetic characteristics. Microbial electrolysis cell (MEC) produces hydrogen from organic matter using exoelectrogenic bacteria. Shewanella oneidensis stands out for having the capacity to produce hydrogen using different electron transfer mechanisms. The present research aims to evaluate the hydrogen production efficiency in a MEC inoculated with a pure culture of S. oneidensis in different operational conditions. Since the use of a catalyst accounts for most of the MEC cost, no catalyst was used for anode or cathode. Experiments were performed in semi-continuous and batch mode using different electrodes, voltages applied, and medium in aerobic and anaerobic conditions. The highest hydrogen production rate (HPR) was 0.107 m3 of H2/m3day obtained in a semi-continuous experiment using graphite plates and stainless steel electrodes. In batch experiments, a HPR occurred at 0.7V, with a value of 0.048 m3 of H2/m3day versus 0.037 m3 of H2/m3day with 0.9V. HPR was higher with carbon felt electrode (0.056 m3 of H2/m3day). However, current density dropped after 38h, with carbon felt electrodes, and did not recover. Results of the present research showed that the MEC using a pure culture of S. oneidensis can be considered an alternative for hydrogen production without using a catalyst. Also, S. oneidensis produced hydrogen in both anaerobic and aerobic conditions with low methane production. Optimization can be proposed to improve hydrogen production based on the operational conditions tested in these experiments.

Hybrid CFD/techno-economic assessments of carbon capturing combustion system integrated with PEM electrolyzer for efficient hydrogen production

The issue of global warming is a significant challenge in the field of environmental science, resulting primarily from the burning of fossil fuels and the subsequent increase in greenhouse gas (GHG) emissions, thus emphasizing the importance of utilizing renewable energy vectors, carbon capture technology, oxy-fuel combustion, and carbon-free fuels like hydrogen to mitigate these negative effects. In this study, the possibility of utilizing low-calorific value biogas in a gas turbine (GT) combustor under various combustion conditions is numerically simulated, and techno-economic analysis of energy systems coupled with the GT combustor is conducted. Herein, two distinct energy systems utilizing different combustion modes for H2 production via PEM electrolyzer have been designed and examined. This investigation focuses on the impact of various influencing factors in oxy-fuel combustion mode, such as the equivalence ratio and the O2 content in the two types of oxidizers, on the rate of hydrogen production, power generation, energy/exergy efficiencies, and the economic index of the proposed energy system. Additionally, a suitable system for large-scale operation is identified among the presented systems. The findings of the study demonstrate that the energy system based on the O2/CO2 combustion mode exhibits a higher rate of hydrogen production compared to the O2/H2O combustion mode and particularly, within the equivalence ratio range of 0.55≤ϕ ≤ 0.85, the hydrogen production rate in the O2/CO2 combustion mode decreases from 5.16 kg/h to 3.72 kg/h.

Synergistic effect of interstitial phosphorus doping and MoS2 modification over Zn0.3Cd0.7S for efficient photocatalytic H2 production

ZnxCd1-xS photocatalysts have been widely investigated due to their diverse morphologies, suitable band gaps/band edge positions, and high electronic mobility. However, the sluggish charge separation and severe charge recombination impede the application of ZnxCd1-xS for hydrogen evolution reaction (HER). Herein, doping of phosphorus (P) atoms into Zn0.3Cd0.7S has been implemented to elevate S vacancies concentration as well as tune its Fermi level to be located near the impurity level of S vacancies, prolonging the lifetime of photogenerated electrons. Moreover, P doping induces a hybridized state in the bandgap, leading to an imbalanced charge distribution and a localized built-in electric field for effective separation of photogenerated charge carriers. Further construction of intimate heterojunctions between P-Zn0.3Cd0.7S and MoS2 accelerates surface redox reaction. Benefiting from the above merits, 1 % MoS2/P-Zn0.3Cd0.7S exhibits a high hydrogen production rate of 30.65 mmol·g−1·h−1 with AQE of 22.22 % under monochromatic light at 370 nm, exceeding most ZnxCd1-xS based photocatalysts reported so far. This work opens avenues to fabricate examplary photocatalysts for solar energy conversion and beyond.

The Influence of Catalyst Loading on Electrocatalytic Activity and Hydrogen Production in PEM Water Electrolysis

The climate change caused by the widespread and continuous use of fossil fuels is a problem that needs to be addressed urgently. One of the solutions offered is through an energy transition towards the use of new or renewable and low-carbon fuels. Hydrogen gas as a carrier of energy is an alternative solution that has attracted the attention of researchers, due to its high combustion energy and environmental friendliness. The production of hydrogen gas using the Proton Exchange Membrane Water Electrolysis (PEMWE) method is considered effective for large-scale production. This study investigates the impact of catalyst loading and various current densities on hydrogen production in the PEM water electrolysis process, utilizing the Cu2O/C catalyst. This study investigates the impact of catalyst loading and different current densities on hydrogen production in the PEM water electrolysis process, utilizing the Cu2O/C catalyst. The electrode catalytic properties were evaluated using the Cyclic Voltammetry (CV) method to determine the Electrochemical Surface Area (ECSA) and the Electrochemical Impedance Spectroscopy (EIS) method to determine the electrical conductivity. The ECSA and EIS measurements demonstrated that the best results were obtained at a higher catalyst loading of 2 mg/cm2 with an ECSA value of 0.21 m2/g and electrical conductivity of 3.04 × 10−6 S/cm. The production of hydrogen results showed that the highest hydrogen production rate was 3.75 mL/s with a catalyst loading of 2.5 mg/cm2, indicating that increasing the load could lead to a higher rate of hydrogen gas production, but this is highly dependent on the surface area utilized. Additionally, at higher current densities, the cell resistance in the electrolysis process may decrease, leading to reduced electrode efficiency for hydrogen production. Thus, the use of high currents may not always be advantageous in hydrogen production using the PEM water electrolysis method.

Fabrication of ZnO-carbon dots composite via microcrystalline cellulose for enhanced photocatalytic hydrogen production under simulated sunlight irradiation

The composite ZnO@CDs was prepared via the hydrothermal method. Microcrystalline cellulose (MCC) was used as the source of carbon dots (CDs). X-ray diffraction, Fourier transform infrared spectrometry, scanning electron microscopy, and transmission electron microscopy analyses were used to characterize the structure and morphology of ZnO@CDs. The prepared ZnO showed a flake morphology with the exposed plane of (001). The X-ray photoelectron spectroscopy and photoluminescence spectroscopy (PL) characterization showed that CDs can be produced by decomposition of MCC and then attached on the surface of ZnO. The photocatalytic properties of ZnO@CDs were investigated under simulated sunlight irradiation. The hydrogen production reached 1240 µmol·g-1 in 30 min, which was much higher than the bare ZnO. The mechanism for the enhanced catalytic property of ZnO@CDs was studied. A high hydrogen production rate (2480 µmol·g-1·h-1) in the short term would enable ZnO@CDs to work as an emergency power supply by hydrogen production and use for restoring electricity and wireless communication in complicated situations.

Efficient Photoelectrocatalytic glycerol to dihydroxyacetone synergistic hydrogen production on Co-LDH nanowires modified TiO2 nanorod arrays

The highly selective conversion of glycerol into high value-added products, accompanied by hydrogen generation, through photoelectrocatalytic technology represents an upcycling process that enhances resource utilization and sustainability. In this study, we designed a composite photoanode with a Type II heterojunction structure, Co-LDH(6 h)/TiO2, achieving a high glycerol conversion rate (1083.22 mmol·m−2·h−1) and hydrogen production rate (20.35 mmol·m−2·h−1) while maintaining a high level of DHA selectivity (48 %). Characterization revealed that the engineered Type II heterojunction significantly enhanced visible light absorption and charge separation, thereby reducing electron-hole recombination and improving the efficiency of glycerol conversion and hydrogen production. Furthermore, it was confirmed by in-situ Fourier transform infrared that the Co-LDH(6 h)/TiO2 composites exhibited significant affinity for adsorption intermediate hydroxyl group in glycerol and rapid desorption of DHA, which is a critical factor in achieving high selectivity for the oxidation pathway to DHA. Mechanistic analyses and isotopic labelling indicate that the photogenerated holes in the Co-LDH(6 h)/TiO2 photoanode are the primary active species responsible for the oxidation of glycerol, yielding a spectrum of valuable products. This research provides a novel strategy and in-depth understanding for developing efficient photoanodes for selective oxidation in organic reactions.

Enhanced hydrogen production through cracking of ammonia water using liquid plasma on titanate-based perovskite catalysts

In this study, a mass production of hydrogen was studied through cracking of ammonia water using liquid plasma. A new FexNi1-xTiO3 perovskite composite with significantly improved visible-light sensitivity was synthesized to further improve the photochemical reaction activity. It is applied to hydrogen production from the decomposition of ammonia water using liquid plasma. In this reaction, a large amount of hydrogen is produced with a small amount of nitrogen gas; moreover, oxygen is produced by liquid plasma discharge and no CO2 byproduct is produced. Titanate-based perovskite catalysts have also been used in decomposition reactions. Titanate-based perovskite catalysts exhibiting high rates of hydrogen production during decomposition were obtained for the plasma and photocatalytic decomposition of aqueous ammonia. FexNi1-xTiO3, which is a newly synthesized ABTiO3-type titanate, showed a higher rate of hydrogen production (approximately 140 L/(g·h)) than other titanate-based perovskites. Furthermore, the FexNi1-xTiO3 exhibited the highest sensitivity to UV and visible light. Its high photosensitivity helped improve the photocatalytic activity in the decomposition of ammonia in water using plasma.

Synchronized sulfur resource recovery and hydrogen production via a self-powered system based on multifunctional Co3S4 catalyst

Self-driven recycling of sulfur-containing wastewater and hydrogen production is a novel concept that integrates environmental protection and new energy development. In this study, we designed for the first time a Zn-air battery self-driven coupling system for the hydrogen evolution reaction (HER), sulfur oxidation reaction (SOR) and developed a trifunctional catalyst suitable for this system capable of HER, SOR, and oxygen reduction reaction (ORR). By synthesizing cobalt sulfide (Co3S4) in situ on nickel foam (NF), we obtained Co3S4/NF monolithic catalyst. It only requires 0.312 V and 0.244 V in SOR and HER, respectively, at 100 mA cm−2. Based on this achievement, the SOR||HER coupled electrolysis system was assembled, which achieved 0.69 V at 100 mA cm−2. Furthermore, the Zn-air battery (using Co3S4 as ORR catalyst) could spontaneously drive the SOR||HER system to achieve high-rate hydrogen production. These findings provide promising opportunities for zero-energy consumption H2 production and recycling of sulfur-containing wastewater.

Hydrogen sulfide methane reforming: A kinetic modeling and techno-economic analysis study

Hydrogen sulfide (H2S) methane (CH4) reforming (H2SMR) is a promising process for sustainable energy production from conventional fuels, offering triple benefits for generating clean hydrogen (H2), consuming toxic H2S, and producing an economically valuable by-product carbon disulfide (CS2). In this work, we studied the optimal operating conditions and assessed the economic feasibility of the non-catalytic H2SMR process, employing a combination of kinetic modeling, process modeling, and techno-economic analysis. Plug flow reactor simulations were performed with our newly developed mechanism to shed light on the optimal operating conditions. It was concluded that a H2S/CH4 molar feed ratio of 2 results in the highest hydrogen production rate, and a feed ratio of 1–2 and a temperature of 1100–1300 °C are needed to maximize the CS2 production rate. However, feed ratios higher than 2 increase the conversion rate of CH4 and therefore benefit the purity of the H2 product. Comparing the cases for a feed ratio of 2 at 1300 °C and a feed ratio of 9 at 1200 °C, the cost is significantly higher for the feed ratio of 9, mainly attributed to the higher electricity cost for higher inlet flow rate and H2S recycling, as well as the cost for the additional steam required during the preheating process. The cost of hydrogen production by H2SMR process could be as low as $1.47/kgH2 for a feed ratio of 2 and solar PV as an energy source, which is more competitive than a cost of $1.97/kgH2 for the steam methane reforming process. Furthermore, since CS2 is a valuable by-product, the higher amount of CS2 formed at a feed ratio of 2 becomes the main source of revenue, which completely covers the cost of hydrogen production. This study demonstrates the huge potential of H2SMR process as a clean and economic-competitive way to produce hydrogen.

Tuning Electrons Migration of Dual S Defects Mediated MoS2-x/ZnIn2S4-x Toward Highly Efficient Photocatalytic Hydrogen Production.

Photocatalytic hydrogen production is a prevalent method for hydrogen synthesis. However, high recombination rate of photogenerated carriers and high activation energy barrier of H remain persistent challenge. Here, the two-step hydrothermal method is utilized to prepare dual S-defect mediated catalyst molybdenum sulfide/zinc indium sulfide (MSv/ZISv), which has high hydrogen production rate of 8.83 mmolg-1h-1 under simulated sunlight. The achieved rate is 21.91 times higher than pure ZnIn2S4 substrate. Defects in ZIS within MSv/ZISv modify the primitive electronic structure by creating defect state that retaining good reducing power, leading to the rapid separation of electron-hole pairs and the generation of additional photogenerated carriers. The internal electric field further enhances the migration toward to cocatalyst. Simultaneously, the defects introduced on the MoS2 cause electron rearrangement, leading to electron clustering on both S vacancies and edge S. Thereby MSv/ZISv exhibits the lowest activation energy barrier and |ΔGH*|. This work explores the division of synergies between different types of S defects, providing new insights into the coupling of defect engineering.

Interfacial charge transfer complexes between ZnO and benzene derivatives: Characterization and photocatalytic hydrogen production

The interfacial charge transfer (ICT) complex formation is a simple procedure to bring optical absorption of wide-bandgap oxide materials in the visible spectral range, crucial for enhancing their use in photo-driven reactions. The optical absorption of the prepared ICT complexes between ZnO and five different colorless benzene derivatives is red-shifted compared to pristine ZnO nanopowder. The density functional theory (DFT) calculations provided realistic energy level alignment in hybrid systems. Also, the DFT-calculated infrared spectra support the binding structures derived based on experimental measurements of free and adsorbed ligands onto ZnO surfaces. The photocatalytic performance of prepared hybrids was evaluated using photocatalytic hydrogen generation in the water-splitting reaction. The ZnO nanopowders modified with catechol and caffeic acid have over 50% higher hydrogen production rate than pristine ZnO, displaying steady hydrogen production under long-run working conditions.

Design of a novel tubular membrane reactor with a middle annular injector for enhancement of dry reforming towards high hydrogen purity: CFD analysis

This study introduces a novel design of a tubular porous membrane catalytic reactor (TPMCR) with a middle annular injector, which aims to improve the performance of a dry reforming of methane (DRM) process. A computational fluid dynamics (CFD) model is developed for a fundamental configuration and subsequently verified using experimental data. The validated CFD model is utilized to examine the influence of different parameters, such as feed composition, inlet gas temperature and pressure, and injection rate, on the reactor performance. The study findings reveal that the introduction of a secondary gas during the injection process has the potential to regulate the process and positively affect the production rates of hydrogen and carbon monoxide. The optimal inlet temperature to attain the highest rate of hydrogen production is determined to be 900 K. The hydrogen selectivity is found to increase from 0.96 to 1.60 with the injection of pure steam when the injection rate is increased from 50 to 500 kg/(m2.s). In addition, the carbon monoxide selectivity is decreased from 6.30 to 2.67. The implementation of a middle annular injector within the proposed TPMCR design offers the potential for enhancing the efficiency and sustainability of chemical reactors. Consequently, the introduced modification leads to more efficient and environmentally friendly chemical processes, specifically in the realms of syngas and hydrogen production through the DRM process, resulting in improved purity levels.

Reinforcement of methanol catalytic reforming for hydrogen production through Ru-based carbon-coated CeO2 catalyst

Methanol steam reforming for hydrogen production is a highly promising energy technology, due to the high hydrogen intensity of methanol and the appendant hydrogen capture from water. In order to reinforce the hydrogen yield in methanol steam reforming reaction, a series of Ru-based carbon-coated CeO2 catalysts were prepared in this work, using glucose, cellulose and activated carbon as different carbon sources via a hydrothermal method. The results showed that the Ru/CG-CeO2 (glucose) catalyst exhibited a superior catalytic performance at the reaction temperature of 400 °C, with a higher hydrogen production rate (0.276 mol/h) than Ru/CC-CeO2 (cellulose, 0.230 mol/h) and Ru/CA-CeO2 (activated carbon, 0.253 mol/h) catalysts. This was attributed to the synergistic effect between CeO2 and carbon, where the carbon layer formed by glucose enhanced the interaction between the active component and the CeO2 support, which also facilitated the electron transfer effects and resulted in a large amount of oxygen vacancies for Ru/CG-CeO2. This led to a strong adsorption capacity for CO and oxygen-containing species derived from the substrate, thereby improving hydrogen production. Additionally, the catalyst stability and the resistance to carbon deposition were evaluated for all the three catalysts, and Ru/CG-CeO2 catalyst also demonstrated a superior stability and anti-carbon deposition capability.

Evaluation of the effect of increasing the organic load in the thermophilic co-fermentation of sugarcane industry by-products on hydrogen, ethanol and lactic acid generation

The effects of increased organic loading rate (OLR) on H2 production and soluble metabolites in a thermophilic anaerobic fluidized bed reactor (AFBR-AT) at 55 °C were evaluated by the fermentation of vinasse and molasses from sugarcane (at a ratio of 1:1). The OLR varied between 30 and 135 kg COD.m−3.d−1, while the hydraulic retention time (HRT) was fixed at 4 h, and the initial co-substrate concentration varied between 5 and 22.5 g COD.L−1. The thermophilic acidogenic reactor showed a maximum hydrogen yield (HY) (2.49 mmol H2.g−1CODapp) at an OLR of 30 kg COD.m−3.d−1 and a higher hydrogen production rate (HPR) (2.8 L H2.L−1.d−1) at an OLR of 45 kg COD.m−3.d−1. Increasing the OLR negatively influenced H2 production. The results showed an increase in ethanol (EtOH) concentrations of up to 47.3 times and lactic acid (HLa) concentrations of up to 15.2 times when comparing OLRs of 30 and 135 kg COD.m−3.d−1, indicating changes in metabolic pathways for acid formation at organic loads ≥90 kg COD.m−3.d−1. Thermoanaerobacterium was the bacteria with higher relative abundance and was directly involved in H2 production, while Lactobacillus was mainly involved in HLa production in higher OLR, decreasing H2 production instead. Besides that, higher OLRs were favorable for sulfidogenesis and the development of sulfate-reducing bacteria, such as Desulfobacterota, due to the higher COD/sulfate ratio in OLR 135 kg COD.m−3.d−1. According to the metabolic inference in this condition, the enzyme activity of sulfite reductase and sulfite dehydrogenase may have occurred, consuming H+, thereby reducing H2 production.

Efficient Low-temperature Hydrogen Production by Electrochemical-assisted Methanol Steam Reforming.

Methanol steam reforming (MSR) provides an alternative way for efficient production and safe transportation of hydrogen but requires harsh conditions and complicated purification processes. In this work, an efficient electrochemical-assisted MSR reaction for pure H2 production at lower temperature (~140 °C) is developed by coupling the electrocatalysis reaction into the MSR in a polymer electrolyte membrane electrolysis reactor. By electrochemically assisted, the two critical steps including the methanol dehydrogenation and water-gas shift reaction are accelerated, which is attributed to decreasing the methanol dehydrogenation energy and promoting the dissociation of H2 O to OH* by the applied potential. Furthermore, the reduced H2 partial pressure by the hydrogen oxidation and reduction process further promotes MSR. The combination of these advantages not only efficiently decreases the MSR temperature but also achieves the high rate of hydrogen production of 505 mmol H2 g Pt -1 h-1 with exceptionally high H2 selectivity (99 %) at 180 °C and a low voltage (0.4 V), and the productivity is about 30-fold than that of traditional MSR. This study opens up a new avenue to design novel electrolysis cells for hydrogen production.