Hydrogen Production In Reactor Research Articles

Triphase photocatalytic water-gas-shift reaction for hydrogen production with enhanced interfacial diffusion at gas–liquid–solid interfaces

Supporting Rh/TiO2 on hydrophobic gas diffusion layers enhanced the photocatalytic WGS for H2 production. Triphase interfaces play a crucial role in interfacial CO mass transfer, especially at low CO concentrations.

Hydrodynamic Effects of Static Liquid Height in the Thermolysis Reactor for Cu-Cl Cycle Hydrogen Production

Hydrodynamic Effects of Static Liquid Height in the Thermolysis Reactor for Cu-Cl Cycle Hydrogen Production

Synthesis of Co3O4 electrodes by electrochemical deposition for water splitting reaction

Introduction: The use of Ni foam substrates for the growth of catalysts is a common practice in electrochemical water splitting reactions, although their stability in some electrolytes can be problematic, hindering the scalability of synthesis. This study aims to explore alternative substrates for catalyst growth, focusing on cobalt oxide (Co3O4) due to its potential in enhancing electrochemical water splitting efficiency. Methods: Cobalt oxide (Co3O4) was synthesized on various conductive substrates including fluorine-doped tin oxide (FTO), indium-doped tin oxide (ITO), and carbon cloth (CC), employing electrochemical deposition techniques. The morphological and crystalline properties of the Co3O4 coatings on these substrates were characterized and analyzed to understand their influence on the catalyst's performance in water splitting reactions. Results: The electrochemical deposition resulted in a more condensed coverage of Co3O4 on the CC substrate, attributed to the crystal's oriented aggregation. The crystallization and lattice development of Co3O4 varied significantly across different substrates, exhibiting high crystallization on FTO and ITO substrates but poorer crystallization on the CC substrate. Notably, the Co3O4/CC electrode demonstrated superior performance in hydrogen evolution reaction, achieving the lowest overpotential of -382 mV at a current density of 10 mA cm-2. Conclusion: The findings suggest that carbon cloth (CC) presents a promising alternative to Ni foam substrates for the growth of Co3O4 catalysts in electrochemical water splitting applications. The enhanced performance of Co3O4/CC electrodes, particularly in terms of overpotential and crystallization behavior, highlights the potential of using CC substrates to improve the efficiency and scalability of water splitting reactions for sustainable hydrogen production.

Mo–P sites boosting interfacial charge transfer of 2D/3D MoS2/TiO2 heterostructure for efficient photocatalytic hydrogen production and chromium(vi) reduction

Spatial separation of photogenerated carriers via the active Mo–P sites on 2D/3D phosphorous-doped MoS2/TiO2 heterostructure can realize the highly efficient photocatalytic hydrogen production and Cr(vi) reduction.

Mixed-conducting ceramic membrane reactors for hydrogen production

Mixed-conducting ceramic membrane reactors for hydrogen production

Nanostructured p-PbS/p-CuO sulfide/oxide bilayer heterojunction as a promising photoelectrode for hydrogen gas generation

Abstract Recently, the photoelectrochemical (PEC) water-splitting reaction for hydrogen (H2) production has been a competitive research route to realize clean and sustainable electric power. In this work, copper oxide (CuO) and PbS thin films were fabricated on commercial glass, respectively, using the techniques of successive ionic-layer adsorption and reaction and chemical bath deposition. These nanostructured thin films served successfully as photoelectrodes for the photogeneration of H2. In addition, a p-PbS/p-CuO bilayer system was also fabricated, and a remarkable boost in PEC efficiency was observed compared to pure CuO and PbS thin films. Optical examinations showed excellent absorbance properties of the p-PbS/p-CuO bilayer in the visible range, with a bandgap of ∼1.28 eV. X-ray diffraction analysis indicated a monoclinic CuO/cubic PbS crystalline structure with a particle size of ∼18 nm. The photocurrent density (J ph) values were obtained using a three-electrode electrochemical cell in 0.3 M Na2S2O3 electrolyte. The p-PbS/p-CuO photoelectrode demonstrated a J ph value of −0.390 mA cm−2, which is significantly higher than the values of −0.120 and −0.008 mA cm−2 for the pure PbS and CuO photoelectrodes, respectively. This improvement is attributed to the p-PbS/p-CuO oxide/sulfide bilayer heterojunction, which improved the visible light absorption and reduced the electron–hole (e–h) recombination. The effects of pH value, temperature light intensity, and wavelength were all additionally studied. Remarkably, the photoelectrodes were stable under a pH of ∼7, which makes them promising for H2 production using normal drinking/seawater. These findings confirm the ability of the prepared photoelectrodes to facilitate water splitting and H2 generation under various environmental, chemical, and illumination conditions.

Rational design of adenine appended synthetic cobalt catalysts via click reaction for electrocatalytic hydrogen production

Green hydrogen has emerged as a critical component in the upcoming renewable energy landscape. Enzyme architecture remains the prime inspiration for designing environment-friendly, efficient, and economical H2 production catalysts from water. The strategic incorporation of peripheral protic functionalities around synthetic metal cores specifically impacts the electrocatalytic H2 evolution reactivity. Here, we have deployed a click chemistry methodology to incorporate a 1,2,3-triazole linker in either meta vs. para position to connect a cobaloxime core with nucleobase adenine. The variation in specific positioning (meta vs. para) of the linker creates two isomeric ligands and their corresponding cobaloxime derivatives. The trifunctional ligand motif positively influences the reactivity of the cobaloximes, as the para-substituted complex produces H2 at a rate of 5350 s−1 with an overpotential <350 mV in near-neutral aqueous conditions. The meta-substituted complex displayed relatively slower catalysis (rate 3700 s−1), albeit with similar energy efficiency under analogous conditions. These robust catalysts also demonstrated substantial H2 production from water under photocatalytic conditions with an appreciable turnover number (TON) of 150 and 100 for the para- and meta-substituted complexes, respectively. The complementary electrochemical and spectroscopic techniques indicate the designed ligand's dual effect (electronic and peripheral) on the catalytic reactivity, where the para-substituted pyridinyl ligand displayed better reactivity than the meta-derivative.

Minireview on the Electrocatalytic Ammonia Oxidation Reaction for Hydrogen Production and Sewage Treatment

Minireview on the Electrocatalytic Ammonia Oxidation Reaction for Hydrogen Production and Sewage Treatment

Kinetic Study of the Aluminum–water Reaction Using NaOH/NaAlO2 Catalyst for Hydrogen Production from Aluminum Cans Waste

The presence of oxide layers covering the surface of aluminum is known to impede the hydrogen production reaction. These oxide layers can be broken by adding catalysts and increasing the aluminum-water reaction temperature. Common catalysts used are alkaline catalysts that are capable of achieving high hydrogen production rates in a short time at lower temperatures, while intermediate temperatures of above 50 °C can accelerate the hydration reaction of the oxide layer. Herein, the mixture of NaOH and NaAlO2 catalysts was employed to attain a stable NaAlO2 solution and continuous reaction of NaOH and aluminum. This research analyzes the influence of temperature between 32 and 80 °C on the aluminum, 0.3 M NaOH and 0.001 M NaAlO2 catalysts solution at atmospheric pressure. All solutions produces a similar hydrogen yields and rate. Solutions containing NaAlO2 indicate reverse reaction that surpressing the Al(OH)3 precipitation. Residue from the reaction is investigated using X-ray Diffraction (XRD), Fourier Transform Infra Red (FTIR), and Scanning Electron Microscope (SEM). The volume of hydrogen produced is evaluated using a mathematical mass reduction and shrinking core model. The rate of hydrogen production depends largely on the aqueous solution's temperature, with an activation energy of 47.4 kJ/mol. Based on the findings, it is readily apparent that the reaction only produced gibbsite and bayerite, with gibbsite and bayerite being dominant at 32–70 °C and 80 °C, respectively. The mass reduction model fits well with the present results with only an average 5.1 mL deviation, whereas the shrinking core model generally tends to result in underestimated values with an average deviation of 23.9 mL. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Regulating the Band Structure of Ni Active Sites in Few‐Layered Nife‐LDH by In Situ Adsorbed Borate for Ampere‐Level Oxygen Evolution

AbstractRealizing rapid transformation of hydroxide to high‐active oxyhydroxide species in layered double hydroxide (LDH) catalyst plays a significant role in enhancing its activity toward oxygen evolution reaction (OER) for hydrogen production from water. Here, a scalable strategy is developed to synthesize defect‐rich few‐layered NiFe‐LDH nanosheets (f‐NiFe‐LDH‐B) with in situ borate modified for boosted and stable OER due to that the borate can narrow the bandgap for Ni sites to realize a more conductive electronic structure. Besides, the adsorbed borate can tune the d band center of Ni sites to promote of hydroxide transformation and facilitate the adsorption of the OER intermediates. The f‐NiFe‐LDH‐B catalyst, therefore, requires only 209 and 249 mV overpotential to deliver 10 and 100 mA cm−2 OER, respectively, with a Tafel slope of 43.5 mV dec−1. Moreover, only 1.8 V cell voltage is required to reach Ampere‐level overall water splitting for 500 h at room temperature.

Iridium-Cooperated, Symmetry-Broken Manganese Oxide Nanocatalyst for Water Oxidation.

The water oxidation reaction, the most important reaction for hydrogen production and other sustainable chemistry, is efficiently catalyzed by the Mn4CaO5 cluster in biological photosystem II. However, synthetic Mn-based heterogeneous electrocatalysts exhibit inferior catalytic activity at neutral pH under mild conditions. Symmetry-broken Mn atoms and their cooperative mechanism through efficient oxidative charge accumulation in biological clusters are important lessons but synthesis strategies for heterogeneous electrocatalysts have not been successfully developed. Here, we report a crystallographically distorted Mn-oxide nanocatalyst, in which Ir atoms break the space group symmetry from I41/amd to P1. Tetrahedral Mn(II) in spinel is partially replaced by Ir, surprisingly resulting in an unprecedented crystal structure. We analyzed the distorted crystal structure of manganese oxide using TEM and investigated how the charge accumulation of Mn atoms is facilitated by the presence of a small amount of Ir.

Kinetic simulation of hydrogen production reaction parameters based on TiO2 photocatalyst

Hydrogen is a clean, efficient, and renewable energy source with significant potential to reduce greenhouse gases. Solar photocatalytic water splitting is a promising and sustainable route to produce hydrogen. Currently, the strategies to improve the efficiency of photocatalytic hydrogen production are mainly focused on the development of sustainable photocatalysts. However, the extent to which multiple working conditions affect photocatalytic hydrogen production efficiency is not yet clear. This paper established a TiO2-based photocatalytic phenomenological kinetic model and then validated it using experimental data to clarify the impact of the combined effects of various reaction conditions on the efficiency of photocatalytic hydrogen production. The effects of photocatalyst dosage, reaction temperature, sacrificial agent concentration, and other decisive parameters on TiO2-based photocatalytic hydrogen evolution performance were analyzed under light intensity of 365 nm. The optimization results revealed that the maximum STH efficiency of 5.30 % was observed, at the reaction temperature of 348.15 K and 0.25 g/L photocatalyst concentration. The model provides insights into the combined effects of different factors on photocatalytic efficiency. The identified optimal reaction conditions relationships are helpful to provide guidance for efficient designing of solar photocatalytic hydrogen evolution systems.

Pt nanoclusters modified porous g-C3N4 nanosheets to significantly enhance hydrogen production by photocatalytic water reforming of methanol

For the use of green hydrogen energy, it is crucial to have efficient photocatalytic activity for hydrogen generation by water reforming of methanol under mild conditions. Much attention has been paid to g-C3N4 as a promising photocatalyst for the generation of hydrogen. To improve the separation of photogenerated charge, porous nanosheet g-C3N4 was modified with Pt nanoclusters (Pt/g-C3N4) through impregnation and following photo-induced reduction. This catalyst showed excellent photocatalytic activity of water reforming of methanol for hydrogen production with a 17.12 mmol·g−1·h−1 rate at room temperature, which was 311 times higher than that of the unmodified g-C3N4. The strong interactions of Pt–N in Pt/g-C3N4 constructed effective electron transfer channels to promote the separation of photo-generated electrons and holes effectively. In addition, in-situ infrared spectroscopy was used to investigate the intermediates of the hydrogen production reaction, which proved that methanol and water eventually turn into H2 and CO2via formaldehyde and formate. This study provides insights for understanding the photocatalytic hydrogen production in the water reforming of methanol.

The performance improvement method of g-C3N4 based catalyst for hydrogen production from ammonia borane: A DFT investigation

In the study, based on the purpose of efficient catalytic AB for hydrogen production, the photochemical properties influence of metal(Ru, Ni) and nonmetal(B,P) elements doping on the g-C3N4 are studied systematacially. The design method of high performance bifunctional catalyst of photocatalysis and metal catalysis are provided. The results have proved that both non-metals B, P and metal Ru, Ni have an efficient regulatory effect on the band structure of g-C3N4, which make the band gap of the clean monolayer g-C3N4(001) decrease from 1.175 eV to 0.261eV(B-g-C3N4(001)) and 0.671eV(P-g-C3N4(001)), 0.164 eV(Ni-g-C3N4(001)) and 0.260 eV(Ru-g-C3N4(001)), respectively. B element have the better modification effect compared with the P element. The reduction of band gap is attributed to the electronic orbit modification effect of impurity element B, P, Ni, Ru in g-C3N4. Ru metal doped g-C3N4 is reduces the barrier of OH bond breakage of CH3OH(reduced from 4.551 eV to 1.530 eV), which is beneficial to the hydrogen-producing reaction of AB alcoholysis. The construction and design of a new bifunctional catalyst(photocatalysis and metal catalysis) RuNiB@g-C3N4 is an efficient route in catalyze AB for hydrogen production. The process of molecule NH3BH3, CH3OH and H2O adsorbed on the B-g-C3N4 are exothermic process, the adsorption energy are -1.562 eV, -1.392 eV and -1.443 eV, respectively. AB is preferentially adsorbed on the B-g-C3N4 catalyst, increasing the adsorption energy of CH3OH and H2O on B-g-C3N4-based catalysts is beneficial to the hydrogen production from AB. The study provides a theoretical method for the research on the technology of the coupling of metal catalysis/photocatalysis ammonia borane to produce hydrogen.

A computational-fluid-dynamics study on scaling up a single flat membrane reactor for on-site hydrogen production

The accessibility of hydrogen stations has been problematic for remote areas, although the demand for fuel-cell electric vehicles has risen. We propose a 50-Nm3/h on-site hydrogen production system using the accessible liquid-fuel infrastructure. The system integrates a pressurized steam reformer and a catalytic membrane reactor to produce high-purity hydrogen. This study focuses on scaling up our membrane reactor for enhanced hydrogen permeation while maintaining acceptable similarity and performance to make the system compact and effective. We compare three scale-up methods, which keep the inlet Reynolds number, gas hour space velocity, and Damköhler-Peclet number constant, respectively. After selecting the third case for its best similarity, we increase the scale to eight and conclude that any scale beyond four is not ideal for our specific membrane reactor. By increasing the scale to four, we reduce the number of reactors for the 50 Nm3/h target by 91% while achieving a hydrogen recovery of 91%. Future studies can refer to the scale-up process that maintains the reactor similarity and high performance in this work for choosing an appropriate scale for membrane reactors.

Computational Study of Transport Phenomena at the Microscale: Effects of Washcoat Thickness and Characteristic Length on the Heat and Mass Transfer Processes in Millisecond Reactors for Hydrogen Production

Computational Study of Transport Phenomena at the Microscale: Effects of Washcoat Thickness and Characteristic Length on the Heat and Mass Transfer Processes in Millisecond Reactors for Hydrogen Production

Unveiling enhanced dark photocatalysis: Electron storage-enabled hydrogen production in polymeric carbon nitride

Researchers have successfully replicated light-driven reactions of natural photosynthesis on semiconductors. However, an important problem limiting practical applications of these reactions is their dependence on light. Catalytic activity of the semiconductors is lost once light ceases, as the generation of charge carriers (i.e., electron-hole pairs) stops. In light of this problem, photosynthetic reactions in the dark are worthy of extra attention. Despite several reports on dark photocatalysis, the energy conversion efficiency remains low, and the mechanism is unclear. In this study, we developed an artificial photocatalytic system capable of decoupling the light and dark hydrogen production reactions. The system is composed of polymeric carbon nitride (PCN), in which electron storage sites are deliberately created. By tuning the number of the electron storage sites in the system, a record hydrogen production rate of 1480 μmol g−1 h−1 was achieved after termination of the visible-light (λ > 420 nm) illumination. In-situ spectroscopic techniques reveal that these electron reservoirs are composed of cyanamide groups capable of storing electrons. Moreover, these electron reservoirs can be excited and show surface plasmon resonance (SPR) effects, leading to the enhanced optical absorption. Importantly, the oxidation side of the dark photocatalytic reaction is found to stem from a cascade reaction involving hole-derived radicals rather than electron-generated oxygenic species reported in literature. We established a complete and stepwise dark photocatalytic reaction process as well as distinguished a rate-determining step.

Criteria for the use of 1D and 2D models in catalytic membrane reactor modeling

A criterion was developed to determine the necessity of using 1D or 2D methods for modeling a concentric tubular membrane reactor for hydrogen-producing reactions. Four dimensionless parameters were defined to provide a complete description of the physical and chemical systems, and the effects of each parameter on the difference between a 1D and 2D model were explored. The membrane reactor geometry consisted of a tube-and-shell configuration with a catalyst bed in the tubular section and a perm-selective membrane in the interphase. The four dimensionless parameters consisted of the Damköhler number (Da), which relates the reaction and axial convection rates, the Péclet number (Pe), which relates the radial diffusion and axial convection rates, the transport parameter (θ), which relates the axial convection and membrane permeation rates, and the equilibrium parameter (ε), which is a measure of the favorability of the reaction. A cutoff at which 1D and 2D model results have less than a 1% difference in final concentrations was used to define a critical Pe value, or Pecrit. Then, a criterion equation was fitted using non-linear regression so that any system can be calculated and compared against Pecrit. Using this criterion, a model above the cutoff (Pe > Pecrit) can reduce computation time by selectively calculating a simple 1D model for conditions, while a model below the cutoff (Pe ≤ Pecrit) should use a more computationally expensive 2D model to assure accuracy. The final criterion was validated against literature data for both 1D and 2D models.

A novel model of a hydrogen production in micro reactor: Conversion reaction of methane with water vapor and catalytic

This study presents a comprehensive investigation of a thermally integrated membrane micro reactor for efficient hydrogen production through the conversion of methane with water vapor. The reactor design incorporates a catalytic Au/ZnO system to enhance performance. The effects of key operational variables, including inlet gas flow rate, pressure, temperature, water-to-methane ratio, and membrane thickness, were examined. Optimal conditions were sought to maximize methane conversion, hydrogen yield, and minimize carbon monoxide production. As feed flow increases, methane conversion decreases due to reduced retention time in the reactor. This decrease is almost six times greater at 240 °C than at 270 °C. Higher water-to-methane ratios improved methane conversion and reduced hydrogen and carbon monoxide production. Shell pressure affected methane conversion, with higher pressures resulting in decreased rates and carbon monoxide levels. As shell airflow velocity increases, methane conversion rises about 0.96 %. Tube pressure influenced hydrogen passage through the membrane, causing decreased hydrogen output from the tube section and increased output from the shell section, while reducing carbon monoxide emissions. These findings contribute to the optimization of a thermally integrated membrane micro reactor for efficient hydrogen production through water vapor-methane conversion.

Facile fabrication of amorphous NiFeP nanosheets to promote urea oxidation reaction for energy-saving hydrogen production

Facile fabrication of amorphous NiFeP nanosheets to promote urea oxidation reaction for energy-saving hydrogen production