Selective Production Of Hydrogen Research Articles

Terpyridine Ni(II) Complex Grafted CdS Nanorods for Cooperative Selective Benzyl Alcohol Oxidation and Hydrogen Production.

Efficient utilization of photogenerated charge carriers to realize photocatalytic solar fuel production and oxidative chemical synthesis is a challenging task. Herein, a conventional amidation reaction route is adopted to successfully construct a novel composite photocatalyst composed of a Ni(II)-terpyridine complex with carboxyl groups grafted on CdS nanorods (labeled as CdS@Ni(terpyC)2). Experimental results have unequivocally revealed that the as-fabricated composite catalyst exhibited a remarkable enhancement in photocatalytic activity for the dehydrogenation of benzyl alcohol under visible light, demonstrating superior hydrogen evolution efficiency and benzaldehyde selectivity, surpassing both pristine CdS and the blend of CdS and Ni(terpyC)2. The carrier dynamics study demonstrated that the Ni(terpyC)2 on the surface of CdS could quickly extract the photogenerated electrons of CdS, which reduced the carrier recombination efficiency, further improving the photocatalytic activity of the catalyst. This work illustrates the effect of surface active site engineering on photocatalysis and is expected to shed substantial inspiration on future surface modulation and design of semiconductor photocatalysts.

Single-Atom Electron Pumps Over Transition Metal Chalcogenides Boosting Photocatalysis.

Cocatalyst is of paramount significance to provide fruitful active sites for suppressing the spatial charge recombination toward boosted photocatalysis. Up to date, exploration of robust and stable cocatalysts is remained challenging. Inspired by the intrinsic merits of single-atom catalysts (SACs), such as distinctive electronic structure and high atomic utilization efficiency, single-atom/transition metal chalcogenides (TMCs) is utilized as a model to synthesize CdS-Pd single-atom catalyst (CdS-PdSA) heterostructures. This demonstrates the precise anchoring of isolated metal single-atom catalysts (SACs) onto TMCs through a simple yet effective wet-chemical strategy. The resulting heterostructures exhibit significantly enhanced and stable photocatalytic activity for selective anaerobic organic transformations and hydrogen production under visible light. This enhancement is primarily inferred due to the role of Pd SACs as electron pumps, which directionally trap the electrons photoexcited over CdS, accelerating the spatial charge separation and prolonging the carrier lifespan. The charge transport route and photocatalytic mechanism are elucidated. This work underscores the potential of SACs as cocatalysts in heterogeneous photocatalysis, offering valuable insights for the rational design of atomic-level cocatalysts for solar-to-chemical energy conversion and beyond.

Controlled dispersion of Ni catalyst on N-doped carbon support for stable and selective hydrogen production from formic acid

Formic acid is a liquid organic hydrogen carrier from which hydrogen can be released together with CO2 by catalytic decomposition. The development of supported Ni catalysts for H2 production is important. Here, the effects of Ni state/dispersion are considered. For this purpose, three samples were prepared with about 3 wt% Ni deposited on porous N-doped carbon. The first sample contained predominantly Ni nanoparticles (∼2 nm), the second contained Ni clusters (<1 nm), and the third – single-atom Ni sites. The catalysts showed close activity in the gas-phase reaction. However, a minimum apparent activation energy of 105 kJ/mol and a maximum selectivity towards H2 production of 99% were achieved for the single-atom Ni catalyst. The nature of its single-atom sites was established to correspond to Ni-N4 and Ni-O4, which showed greater stability under the conditions of the catalytic reaction.

Hydrogen Production through Distinctive C-C Cleavage during Acetic Acid Reforming at Low Temperature.

Acetic acid reforming is a green method for sustainable hydrogen production owing to its renewable source from biomass conversion. However, conventional acetic acid reforming would produce various byproducts, including CO, CH4 and so on. Here, we develop a distinctive method for selective hydrogen production from C-C directional cleavage during acetic acid reforming. Completely different from conventional acetic acid reforming process, acetic acid would react with water over organoruthenium catalyst during its C-C cleavage at low temperature, then produce methanol and formic acid (CH3COOH+H2O→CH3OH+HCOOH). Lastly, methanol and formic acid could further decompose into hydrogen and carbon dioxide over organoruthenium selectively. As a result, there is little CO and CH4 produced in the first step of C-C bond cleavage during acetic acid reforming at 100 °C. Hydrogen production rate is up to 26.8 molH2/(h-1*mol-1 Ru) at 150 °C through a tandem catalysis. A mechanism for C-C cleavage of acetic acid is proposed based on intermediate product analysis and density functional theory (DFT) calculation. Firstly, the C-C single bond was transformed into C=C double bond by dropping one H atom to organoruthenium. Then the coming H2O molecule reacted with the C=C bond by an addition reaction, forming methanol and formic acid. This research not only proposes distinctive reaction pathway for hydrogen production from acetic acid reforming, but also provides some inspiration for selective C-C bond cleavage during ethanol reforming.

Solar to hydrogen conversion by a 25 cm2-photoelectrochemical cell with upscaled components

An innovative tandem photoelectrochemical cell with a scaled-up active area from 0.25 to 25 cm2 based on low-cost and non-critical raw materials was employed to produce green hydrogen by water splitting. It uses a photoanode/membrane/photocathode tandem cell configuration in which a hematite-based photoanode is layered on a fluorine-doped tin oxide glass for the oxygen evolution reaction, CuO is deposited on a hydrophobic gas diffusion layer as the photocathode for the hydrogen evolution reaction and an anion exchange membrane is used as the electrolyte and gas separator. The solid membrane's low hydrogen and oxygen crossover guarantees the operational stability of the tandem photoelectrochemical cell and the efficient separation of water-splitting products. Significant efforts have been focused on scaling up the cell. It has allowed obtaining, for the first time, a 25 cm2 unit cell prototype. Appropriate design approaches have been considered to optimise water/gas management, current collection, gas-tightness and clamping. The adopted architecture allowed for the reduction of the bias-potential from −1.23 V, generally employed to investigate PEC cells, up to −0.6/-0.4 V 20 h-durability tests demonstrated good resistance to corrosion, showing a constant photocurrent. Efficiency at −0.6 V was about 0.2%. Selective hydrogen production was demonstrated by mass spectrometric analysis.

Nanosensor of gallium nitride for methanol adsorption for producing hydrogen: A computational chemistry study

The selective hydrogen production from methanol on the graphitic-like gallium nitride (GaN) and carbon doped gallium nitride (C–GaN) nanosheets has been challenged using the density functional theory (DFT) method. In this work, we report that GaN and C-doped GaN can catalyze the direct producing hydrogen (H2) of methanol (CH3OH) through Langmuir adsorption. The changes of charge density have shown a more important charge transfer for C-doped GaN compared to GaN which act both as the electron acceptor while CH3OH molecules in water act as the stronger electron donors through adsorption on the GaN and C-doped GaN surfaces. The adsorption of CH3OH molecules on the GaN and C-doped GaN surfaces represented spin polarization in the GaN and C-doped GaN which can be employed as thee magnetic sensors for running the reaction of H2 producing. The partial electron density states based on “PDOS” graphs have explained that the CH3OH states in both of GaN and C-doped GaN nanosheets, respectively, have more conduction bands between −5 eV to −10 eV. The simulated distribution functions of CH3O@GaN and CH3O@C–GaN complexes exhibits that the bond lengths of O–Ga in CH3O–GaN complex is 1.99 Å and O–C in CH3O–C–GaN complex is 1.43 Å. Besides, the plot for electric potential versus atomic charge has been shown around carbon doping of the GaN which presents the electron accepting characteristics of this element via the electron donor of oxygen atom of hydroxyl group in CH3OH with linear relation coefficient of R2 = 0.9948. GaN and C–GaN nanosheets seem to have enough efficiency for adsorption CH3OH molecules through charge transfer from oxygen to the gallium and carbon elements due to intra-atomic and interatomic interactions.

Coprecipitation dispersion of Cu-Zn-Zr mixed oxides nanocatalyst over Si and Al-Based supports applied in selective and stable hydrogen production from Methanol: Experimental study and rate of reaction engineering via intelligent optimization of CFD method

This study focused on evaluating different support materials made of silicon (Si) and aluminum (Al) for improving the properties of catalysts and their ability to produce high-purity hydrogen from methanol. Accordingly, four coprecipitation-supported nano-scale CuO/ZnO/ZrO2 catalysts were fabricated. Accordingly, MCM-41, γ-Al2O3, and activated alumina materials were used as supports for these catalysts. Various methods such as BET, EDX, FESEM, FTIR, PSD, and XRD were used to analyze the prepared catalysts. The results of FESEM and EDX indicated that using activated alumina as a support led to the smallest copper particle size and excellent dispersion on its surface, and prevented the agglomeration of particles. The catalyst made with activated alumina also had the largest surface area, which is beneficial for reactions. This catalyst showed strong methanol conversion ability and produced less undesirable CO during hydrogen production from methanol. Additionally, a stability test lasting 1220 min confirmed that this catalyst maintained consistent performance over time. A novel method combining CFD and genetic optimization algorithms was used to synthesize new catalysts for catalytic steam reforming of methanol. This approach accurately estimated reaction rates and activation energies, achieving an RMSE below 0.01 for all outcomes. The optimal catalyst, CZZ-Al2O3 (A), exhibited activation energies of 73.928 J/mol, 71.261 J/mol, 106.516 J/mol, and 143.217 J/mol with an RMSE of 0.0089.

Promoted oxygen release from copper-ceria interfacial sites for selective hydrogen production

The modulation of oxygen species is an effective strategy for selective H2 production with relevant chemical looping processes. This paper describes the promoted oxygen release from CuO-CeO2 redox catalysts for selective H2 production in chemical looping oxidative steam reforming of methanol (CL-OSRM). Despite the complete oxidation of methanol from CuO, the excess H2 production of CL-OSRM with respect to methanol steam reforming (MSR) increases linearly with the amount of active oxygen in CeO2 induced by the copper-ceria interaction. In situ spectroscopic characterizations and mechanistic study demonstrate that copper-ceria interfacial sites induce oxygen release from CeO2 to facilitate the partial oxidation of methoxy to formate species, which promotes the H2 production rate. This study provides an instructive strategy for the construction of redox catalysts for selective H2 production with chemical looping processes.

Mechanistic Insights on Permeation of Water over Iron Cations in Nanoporous Silicon Oxide Films for Selective H2 and O2 Evolution

Electrocatalysts encapsulated by an ultrathin and semipermeable oxide layer offer a promising avenue for efficient, selective, and cost-effective production of hydrogen through photoelectrochemical water splitting. This architecture is especially attractive for Z-scheme water splitting, for which a nanoporous oxide film can be leveraged to mitigate undesired, yet kinetically facile, reactions involving redox shuttles, such as aqueous iron cations, by limiting transport of these species to catalytically active sites. In this work, molecular dynamics simulations were combined with electrochemical measurements to provide a mechanistic understanding of permeation of water and Fe(III)/Fe(II) redox shuttles through nanoporous SiO2 films. It is shown that even for SiO2 pores with a width as small as 0.8 nm, water does not experience any energy barrier for permeating into the pores due to a favorable interaction with hydrophilic silanol groups on the oxide surface. In contrast, permeation of Fe(III) and Fe(II) into microporous SiO2 pores is limited due to high energy barriers, which stem from a combination of distortion and dehydration of the second and third ion solvation shells. Our simulations and experimental results show that SiO2 coatings can effectively mitigate undesired Fe(III)/Fe(II) redox reactions at underlying electrodes by attenuating permeation of iron cations, while allowing water to permeate and thus participate in water splitting reactions. In a broader context, our study demonstrates that selectivity of solvated cations can be manipulated by controlling the pore size and surface chemistry of oxide films.

Pincer–Ruthenium-Catalyzed Reforming of Methanol─Selective High-Yield Production of Formic Acid and Hydrogen

Pincer–Ruthenium-Catalyzed Reforming of Methanol─Selective High-Yield Production of Formic Acid and Hydrogen

Ruthenium Metal–Organic Frameworks as Stable Nanostructures for Selective Hydrogen Production from Acetaldehyde and Water under Mild Conditions

Hydrogen is a promising energy carrier because it is a wide and sustainable source. However, it is still extremely difficult to store and transport hydrogen safely because of its active chemical properties and harsh explosion limits. Organic liquid is a popular research field for hydrogen production and storage. Inspired by its biological metabolism, here acetaldehyde is innovatively used for hydrogen production. The hydrogen content of an acetaldehyde–water solution is 10.2 wt %, which is slightly lower than that of a methanol–water solution but much higher than that of formic acid and formaldehyde. For the first time, we prepared several ruthenium metal–organic frameworks (MOFs) as stable nanostructures for selective hydrogen production from acetaldehyde and water under mild conditions (∼60 °C). Ru-MOFs all have nanoscale pores, and the turnover frequency of ruthenium 2,3,5,6-tetramethyl-1,4-phenylenediamine for acetaldehyde decomposition is up to 223 h–1 in water at 90 °C. Because C–C bond cleavage is an inevitable step for hydrogen or energy production from C2 organics, ion chromatography, high-performance liquid chromatography, 1H NMR spectroscopy, and mass spectrometry were employed to propose a catalytic process of hydrogen production from acetaldehyde decomposition. We evidently prove that water participates in acetaldehyde decomposition, thereby claiming an acetaldehyde–water reforming process. Additionally, we confirm that formic acid and acetic acid are the intermediates during the hydrogen production process. This research not only holds great promise for hydrogen production from C2 organics at low temperatures, as well as catalytic technology for C–C bond cleavage, but it also provides certain profound scientific insights for hydrogen or energy production from multicarbon organics, such as biomass.

A switchable route for selective transformation of ethylene glycol to hydrogen and glycolic acid using a bifunctional ruthenium catalyst.

The developed bifunctional NNN-Ru complex features a high catalytic efficiency for the selective production of hydrogen and glycolic acid from ethylene glycol under mild reaction conditions, where a TON of 6395 was achieved. Tuning the reaction conditions afforded further dehydrogenation of the organic substrate with higher hydrogen production, and a higher TON of 25 225 was attained. The scale-up reaction yielded 1230 mL of pure hydrogen gas under the optimized reaction conditions. The role of the bifunctional catalyst was studied and mechanistic investigations were performed.

Steam reforming of bio-alcohols over Ni-M (Cu, Co, Pt)/MCF-S (MgO, La2O3, CeO2) for renewable and selective hydrogen production: Synergistic effect of MCF silica and basic oxides on activity and stability profiles

In the current investigation, highly active, and stable catalyst-support systems were developed by employing the benefits of the 3D mesoporous arrangement of MCF silica and O2− Lewis basic sites of MgO, La2O3, and CeO2 in a single system for renewable and selective H2 production via steam reforming (SR) of bio-alcohols, viz., ethanol (SRE), glycerol (SRG), n-butanol (SRB), and ethylene glycol (SREG). The impact of aging time [24, 48, and 72 h ] on structural and surface features of MCF silica was also investigated to develop novel type of mesoporous materials with the best textural properties, viz., Cu-Ni-Co/MCF-MgO for SRE, Ni-Cu/MCF-La2O3 for SRG, Pt-Ni-Cu/MCF-La2O3 for SRB and Ni-Cu/MCF-CeO2 for SREG which were characterized by several physio-chemical techniques; for instance, BET, H2-TPD, H2-TPR, TGA, XRD, TEM, SEM, EDX as well as high-resolution XPS analysis. The efficacy of the combination of MCF silica with basic metal oxides was evident from the results showing nearly complete reactant conversion, no coke formation, high selectivity (>84 % H2 yield), and long-term stability beyond 680 h (> 68 h time on stream (TOS) for one cycle over > 10 cycles) for all bio-alcohols whereas MCF silica without any basic metal oxides, i.e. Ni-Cu/MCF was stable only up to ≤ 64 h (≤ 16 h TOS for one cycle up to ≤ 4 cycles) due to the absence of O2− Lewis basic sites leading to coking. Such a huge difference in catalytic stability between MCF-S (MgO, La2O3, CeO2) and Ni-Cu/MCF catalysts clearly justifies the synergistic effect of the 3D mesoporous structure of MCF silica and O2− Lewis basic sites on high metal dispersion, strong metal-support interaction (SMSI), coke inhibition. It proved their efficacy as potential commercial SR catalysts for sustainable H2 production from bio-alcohols. Finally, catalytic reaction mechanisms were developed for SRE, SRG, SRB, SREG and intrinsic reaction kinetics were studied over their corresponding catalyst-support systems in the absence of external mass transfer and intra-particle diffusion resistancs. The apparent activation energies for SRE, SRG, SRB, and SREG were calculated as 7.2, 11.2, 10.5, and 12.1 kcal/mol, respectively.

Preparation Strategy Using Pre-Nucleation Coupled with In Situ Reduction for a High-Performance Catalyst towards Selective Hydrogen Production from Formic Acid

Formic acid decomposition (FAD) is one of the most promising routes for rapid hydrogen (H2) production. Extensive efforts have been taken to develop efficient catalysts, which calls for the simultaneous regulation of the electronic structure and particle size of the catalyst. The former factor determines the intrinsic performance, while the latter corresponds to the active site utilization. Here, an effective preparation strategy, pre-nucleation coupled with in situ reduction, is developed to realize and well-tune both surface electronic states and particle size of the pallidum (Pd) catalyst. Benefiting from the structural merits, the as-prepared catalyst exhibits high mass-specific activity of 8.94 molH2/(gPd·h) with few carbon monoxide (CO) molecules, and the activation energy could reach a value as small as 33.1 kJ/mol. The work not only affords a highly competitive FAD catalyst but also paves a new avenue to the synthesis of ultra-fine metal nanoparticles with tailorable electronic structures.

Selective Hydrogen Production from Glycerol over Ruthenium Catalyst

AbstractGlycerol – one of the prominent by‐products of biodiesel is also an important source of hydrogen gas. Herein, the efficient and selective production of hydrogen gas from glycerol in water at 90–120 °C over a ruthenium nanoparticle (∼2.7 nm) catalyst is demonstrated. Notably, high yield of hydrogen gas (n(H2)/n(glycerol); 0.96–1.61) was achieved from the glycerol‐water solution, where the reaction temperature and base concentration played crucial role in achieving high yield of H2. Advantageously, under the studied reaction conditions, the ruthenium catalyst also exhibited appreciably high long‐term stability for over 36 h while generating ca. 70 L H2 per gram of Ru with H2 yield of 350 L per L of glycerol. Moreover, high yield for lactic acid is also achieved during the production of hydrogen gas from glycerol.

Nanoscale Assembly of CdS/BiVO4 Hybrids for Coupling Selective Fine Chemical Synthesis and Hydrogen Production under Visible Light.

Simultaneously utilizing photogenerated electrons and holes in one photocatalytic system to synthesize value-added chemicals and clean hydrogen (H2) energy meets the development requirements of green chemistry. Herein, we report a binary material of CdS/BiVO4 combining one-dimensional (1D) CdS nanorods (NRs) with two-dimensional (2D) BiVO4 nanosheets (NSs) constructed through a facile electrostatic self-assembly procedure for the selectively photocatalytic oxidation of aromatic alcohols integrated with H2 production, which exhibits significantly enhanced photocatalytic performance. Within 2 h, the conversion of aromatic alcohols over CdS/BiVO4-25 was approximately 9-fold and 40-fold higher than that over pure CdS and BiVO4, respectively. The remarkably improved photoactivity of CdS/BiVO4 hybrids is mainly ascribed to the Z-scheme charge separation mechanism in the 1D/2D heterostructure derived from the interface contact between CdS and BiVO4, which not only facilitates the separation and transfer of charge carriers, but also maintains the strong reducibility of photogenerated electrons and strong oxidizability of photogenerated holes. It is anticipated that this work will further stimulate interest in the rational design of 1D/2D Z-scheme heterostructure photocatalysts for the selective fine chemical synthesis integrated with H2 evolution.

Selective Production of Hydrogen and Solid Carbon via Methane Pyrolysis Using a Swirl-Induced Point–Plane Non-thermal Plasma Reactor

Selective Production of Hydrogen and Solid Carbon via Methane Pyrolysis Using a Swirl-Induced Point–Plane Non-thermal Plasma Reactor

Cooperative selective benzyl alcohol oxidation and hydrogen production over Pd6(SC12H25)12cluster-coupled CdS nanorods: the key role of water in photocatalytic benzyl alcohol splitting

Atomically precise Pd clusters/CdS nanorod photocatalysts were constructed for photocatalytic cooperative highly selective oxidation of benzyl alcohol to benzaldehyde and H2production.

Advances and Prospects in Metal-Organic Frameworks as Key Nexus for Chemocatalytic Hydrogen Production.

Hydrogen is a clean and sustainable energy carrier, which is considered a promising alternative for fossil fuels to solve the global energy crisis and respond to climate change. Social concerns on its safe storage promote continuous exploration of alternatives to traditional storage methods. In this case, chemical hydrogen storage materials initiate plentiful research with special attention to the design of heterogeneous catalysts that can enhance efficient and highly selective hydrogen production. Metal-organic frameworks (MOFs), a kind of unique crystalline porous materials featuring highly ordered porosities and tailorable structures, can provide various active sites (i.e., metal nodes, functional linkers, and defects) for heterogeneous catalysis. Furthermore, the easy construction of active sites in highly ordered MOFs, which can work as plate for the delicate active site engineering, make them ideal candidates for a variety of heterogeneous catalysts including chemocatalytic hydrogen production. This review concentrates on the application of MOFs as heterogeneous catalysts or catalyst supports in chemocatalytic hydrogen production. Recent progresses of MOFs as catalysts for chemocatalytic hydrogen production are comprehensively summarized. The research methods, mechanism analyses, and prospects of MOFs in this field are discussed. The challenges in future industrial applications of MOFs as catalysts for hydrogen production are proposed.

A Process for Hydrogen Production from the Catalytic Decomposition of Formic Acid over Iridium-Palladium Nanoparticles.

The present study investigates a process for the selective production of hydrogen from the catalytic decomposition of formic acid in the presence of iridium and iridium–palladium nanoparticles under various conditions. It was found that a loading of 1 wt.% of 2% palladium in the presence of 1% iridium over activated charcoal led to a 43% conversion of formic acid to hydrogen at room temperature after 4 h. Increasing the temperature to 60 °C led to further decomposition and an improvement in conversion yield to 63%. Dilution of formic acid from 0.5 to 0.2 M improved the decomposition, reaching conversion to 81%. The reported process could potentially be used in commercial applications.