Mechanism Of Hydrogen Generation Research Articles

Mechanism of hydrogen generation from low melting point elements (Ga, In, Sn) on aluminum alloy hydrolysis

The reaction of aluminum water to produce hydrogen is prevented by an alumina film. To prepare a kind of aluminum alloy with instant hydrogen production and high hydrogen yield, this paper investigates the effect of different Ga content and In–Sn ratio on the hydrogen production performance of aluminum alloy, and also observes the effect of hydrogen production at different temperatures. The composition, structure, and thermal properties are observed by Scanning Electron Microscope, X-ray diffraction, and differential scanning calorimetry. With different ratios of In and Sn, they appear as two intermetallic compounds, In3Sn and InSn4. When Ga, In, and Sn were added to aluminum together, the hydrolytic properties of the Al-Ga-In-Sn alloys are greatly improved. The paper finally prepared an aluminum alloy with a hydrogen conversion rate of more than 98% and activation energy of 39.2 kJ/mol. Further the development and utilization of hydrogen energy are promoted.

Influence of the proton relay spacer on hydrogen electrocatalysis by cobalt hangman porphyrins

A cobalt hangman porphyrin system with a phenyl spacer between the porphyrin ring and an internal carboxylic acid group as well as its non-hangman analogue were synthesized and utilized for the study of the proton-coupled electron transfer (PCET) kinetics attendant to electrocatalytic hydrogen evolution. Cyclic voltammetry (CV) together with simulations show that a short distance between the proton relay and the redox active cobalt center as well as the increased proton donating strength results in superior catalytic activity. The mechanism of hydrogen generation is at the nexus of proton transfer–electron transfer (PTET) and concerted proton–electron transfer (CPET), as opposed to an ETPT mechanism that is characteristic of hangman systems with longer proton relay networks.

Hydrolysis H2 generation of Mg–Ni alloy catalyzed by expandable graphite/stannic oxide

In this work, Mg-10 wt% Ni (M) with higher theoretical hydrogen production is taken as the research object. M − 10C (M = Mg10Ni, C = EG (expandable graphite), SnO2 (stannic oxide), EG-SnO2) composites with various compositions were integrated by high-energy ball milling (HEBM), and their H2 production behavior in simulated seawater were investigated. Not only did X-ray analysis and scanning electron microscopy techniques be used to study the phase composition diffraction pattern and surface morphology of these Mg-based composites in detail, but also the performance and mechanism of hydrogen generation are investigated by initial hydrolysis kinetics. The results demonstrate that the addition of hollow SnO2 nanotubes and lamellar EG to the M alloy make surface loose and porous, and the existing cracks and gaps can increase hydrolysis channels with rapid medium transfer, thereby improving the initial reaction kinetics and the final hydrogen production rates. M − 10C (M = Mg10Ni, C = EG, SnO2, EG-SnO2) composites can produce 98.207, 69.996, 58.235 mL ⋅g−1 H2 within 15 s at 291 K, which are higher than M alloy without any catalyst (38.151 mL⋅g−1 H2). It is worth noting that M-10SnO2 rapidly release 395.4 mL⋅g−1 H2 with 51.35% yield in 2 min at 298 K. The difference between the H2 generation yields is mainly originated from the activity of catalysts on nucleation and growth of Mg(OH)2 in the hydrolysis reaction stage. Moderate initial nucleation rate and the subsequent sufficient growth of Mg(OH)2 nucleus are prerequisites to ensure fast initial hydrogen production rate and high H2 generation yield. Catalysis is an effective means to ameliorate the hydrogen performance of Mg-based alloys, and it is important to choose the appropriate catalyst type. However, the degree of catalysis determined by the content of the catalyst and the manner of addition is also worthy of attention.

Mechanism of hydrogen generation on stable Mo-edge of 2H-MoS2 in water from density functional theory

In this paper, the stable structure of Mo-edge of 2H-MoS2 in water and the H2 evolution mechanism at Mo-edge in 2H-Mo7S17 cluster were investigated by the B3LYP method of the density functional theory. The calculations suggested that the stable structure of the Mo-edge in gas and water was different. The Mo-edge with the upright S bonded by one Mo atom was more stable in water while the S atom of Mo-edge was bonded by two Mo atoms to generate a stable Mo-edge in gas. The adsorption energy of H on S was higher than that on Mo at Mo-edge; as a result, the hydrogen evolution reactions on S and Mo were limited by the Heyrovsky and Volmer step, respectively. In hydrogen evolution reaction, the Volmer reaction occurs on S to produce Mo7S17HS, leading to the aggregation of electron on Mo and thus decreasing the barriers for H2 evolution reaction on Mo. Subsequently, the Mo in Mo7S17HS severing as active sites efficiently catalyzed hydrogen evolution reaction through the Volmer–Heyrovsky mechanism, in which the Volmer reaction was identified as the rate-determining step with a potential barrier of 17.9 kcal/mol, being close to the experimental value of 19.9 kcal/mol.

Hydrogen generation by hydrolysis of Mg-Mg2Si composite and enhanced kinetics performance from introducing of MgCl2 and Si

This paper reported the performance and mechanism of hydrogen generation via hydrolysis of ball-milled Mg-Mg2Si composite (5.3 wt % Si-94.7 wt % Mg) in deionized water and in MgCl2 solution. The results showed that the obtained Mg-Mg2Si composite presented relatively higher hydrogen generation performance than pure magnesium. Adoption of 0.5 M MgCl2 solution to replace deionized water sufficiently and vastly enhanced the hydrolysis properties of the Mg-Mg2Si composite. The composite in 0.5 M MgCl2 solution generated 445 mL/g hydrogen in 5 min, 688 mL/g hydrogen in 10 min and 889 mL/g hydrogen (conversion rate 99%) in 40 min at 328 K. This remarkable improvement is due to that the addition of Si element in the composite and the introduction of MgCl2 in solution, as well as the special preparation process of the materials, could decrease the formation of continuous magnesium hydroxide passive layer on the particle surface, directly or indirectly. Moreover, the apparent activation energies for composite hydrolysis in deionized water, in 0.5 and 2.0 M MgCl2 solution were calculated to be 30.1 ± 0.6, 9.5 ± 0.1 and 3.7 ± 0.2 kJ/mol, respectively. This work demonstrates that the hydrogen generation system based on low-cost and high-performance Mg-Mg2Si composite is very applicable and promising; and it may open a new avenue for onsite hydrogen supply.

9-2-1 アンモニアからの脱水素メカニズムの解明(Session 9-2 水素製造・貯蔵・利用II)

9-2-1 アンモニアからの脱水素メカニズムの解明(Session 9-2 水素製造・貯蔵・利用II)

Non-thermal plasma ethanol reforming in bubbles immersed in liquids

Ethanol reforming in non-thermal plasma generated in atmospheric-pressure argon bubbles immersed in liquid ethanol/water solution is studied using a self-consistent multi-species fluid model. The influence of the dielectric constant of the liquid on the plasma dynamics and its effect on the generation of active species is analyzed. Several modes of discharge are obtained for large liquid dielectric constant. In these modes, we obtain either an axial streamer or a combination of two simultaneous streamers propagating along the bubble axis and near the liquid wall. The influence of these modes on the production of active species is also studied. The main reactions responsible for the generation of molecular hydrogen and light hydrocarbon species are analyzed. A possible mechanism of hydrogen generation in liquid phase is discussed.

Solar Photocatalytic production of hydrogen from aqueous polystyrene-Pt/TiO2 Suspension

In the present work, the Photocatalytic production of hydrogen from aqueous suspension of polystyrene is studied using titanium dioxide doped with platinum as photocatalyst. The parameters affecting the efficiency of Photocatalytic hydrogen production are Pt-loading (%), solution pH and the Pt/TiO2 loading and particle size. Under optimum conditions, 78 micro moles of hydrogen gas is generated after about 25 hr, irradiation in deacrated solution ( pH=13, Pt weight % load is 6% and Pt/TiO2 load and particle size are 4 gm/l and 400 mesh size respectively). Negligible amounts of hydrogen gas were noticed in the presence of unplatinized TiO2 at pH lower than 4. The apparent quantum yield of the Photocatalytic production of hydrogen was also determined and is affected by the % load of Pt on TiO2. The number average molecular weight of polystyrene decreases with irradiation time which indicates the photo degradation process under the condition employed. Carbon dioxide is also evolved at the later stage of photolysis process which suggests the partial mineralization of the polymer during the photolysis process. According to the experimental results a mechanism of hydrogen generation and polymer degradation is suggested.

Function of triazenido compound for electrocatalytic hydrogen production catalyzed by platinum complex

A new type of electrocatalyst based on a triazenido-platinum complex, Pt(PPh3)2(L)Cl (1), is prepared by the reaction of 1-[(2-methoxy) benzene]-3-[2-pyridine] triazene (HL) and Pt(PPh3)2Cl2 in the presence of triethylamine. Electrochemical studies indicate that HL, Pt(PPh3)2Cl2 and 1 can catalyze hydrogen evolution from acetic acid or a neutral buffer. To show triazenido ligand, HL, plays a role in determining the catalytic activities of the platinum complex, we systematically study the electrocatalytic activities of HL, Pt(PPh3)2Cl2 and Pt(PPh3)2(L)Cl and provide a possible catalytic mechanism for hydrogen generation catalyzed by 1.

Base-free non-noble-metal-catalyzed hydrogen generation from formic acid: scope and mechanistic insights.

The iron-catalyzed dehydrogenation of formic acid has been studied both experimentally and mechanistically. The most active catalysts were generated in situ from cationic Fe(II) /Fe(III) precursors and tris[2-(diphenylphosphino)ethyl]phosphine (1, PP3 ). In contrast to most known noble-metal catalysts used for this transformation, no additional base was necessary. The activity of the iron catalyst depended highly on the solvent used, the presence of halide ions, the water content, and the ligand-to-metal ratio. The optimal catalytic performance was achieved by using [FeH(PP3 )]BF4 /PP3 in propylene carbonate in the presence of traces of water. With the exception of fluoride, the presence of halide ions in solution inhibited the catalytic activity. IR, Raman, UV/Vis, and EXAFS/XANES analyses gave detailed insights into the mechanism of hydrogen generation from formic acid at low temperature, supported by DFT calculations. In situ transmission FTIR measurements revealed the formation of an active iron formate species by the band observed at 1543 cm(-1) , which could be correlated with the evolution of gas. This active species was deactivated in the presence of chloride ions due to the formation of a chloro species (UV/Vis, Raman, IR, and XAS). In addition, XAS measurements demonstrated the importance of the solvent for the coordination of the PP3 ligand.

Nanowire–nanoparticle conjugate photolytic device

The present work demonstrates proof of concept of a nanowire–nanoparticle conjugate device that produces hydrogen when suspended in water and exposed to visible radiation. The mechanism of hydrogen generation is attributed to photoelectrochemical cleavage of water. The vanadium oxyhydrate (V3O7·H2O) nanowires are synthesized by a sol-gel procedure and subsequently decorated with Au nanoparticles by reduction chemistry. The nanostructures are characterized by XRD, TEM, EDS, and optical/Raman spectroscopy. The photolytic product is analyzed by gas chromatography. The author discusses various mechanisms, which are unique to the multifunctional nanostructures and improve the photolytic efficiency, such as efficient splitting of photogenerated electron/hole pairs, self-alignment of the Fermi level in Au nanoparticles leading to efficient electron transfer to hydrogen reduction, and optical absorption enhancement in the nanowires by the plasmonic properties of nanoparticles. Conversion and external quantum efficiencies of 5·3% and 11·3% are demonstrated under 470 nm excitation for the first hour of photolysis, respectively.

하이브리드 및 연료전지 연계형 해양구조물용 전력체계

해양구조물 전력시스템은 독립형 전력체계를 구축하기 어렵다. 그러므로 해상용 전력시스템을 효과적으로 운영하기 위하여 연료전지 및 하이브리드 전력체계를 연동한 전력시스템을 구축하는 것이 중요하다. 본 연구에서는 연료전지 기반의 해양구조물용 전력체계 설계에 필요한 수소 발생 메카니즘, 사용 전력량 계산과정 등을 기초로 해상용 연료전지 기반의 전력체계를 설계하고, 설계된 전력 시스템을 LabVIEW 프로그램을 활용하여 시뮬레이션 및 분석하였으며, 이를 기반으로 해양구조물용 전력시스템 설계 방안을 제안하고자 한다. Ocean structure's power system is difficult to construct a stand-alone power system. Therefore, to manage effectively power system of ocean structure, it's important to construct power system which is connected fuel-cell with hybrid power system. This paper designs power system of fuel-cell for the sea based on hydrogen generation mechanism, calculation of using electric power, etc. Designed power system is analysed & simulated using LabVIEW program. And, this paper suggests design method of power system for ocean structure based on analysed & simulated results.

Nanowire-Nanoparticle Conjugate Photolytic Devices

The present work demonstrates hydrogen generation by nanowire-nanoparticle conjugate structures under visible radiation. The mechanism of hydrogen generation is attributed to photolytic cleavage of water. The nanostructures are synthesized by sol-gel and reduction chemistries and characterized by XRD, SEM, TEM, and optical spectroscopy. Photolysis is analyzed by gas chromatography. We discuss the possible mechanisms involved in the observed photolysis in terms of unique attributes of the multifunctional nanostructures, such as efficient channeling of photocarriers to redox reactions at the interfaces and self-alignment of energy levels leading to efficient charge transfer.

Study on Mechanism of Hydrogen Generation from Lubricants

To establish fundamental countermeasures for hydrogen embrittlement that occurs to several kinds of bearings, the mechanism of hydrogen generation from lubricants was studied. Sliding tests were conducted, and the amount of hydrogen generated from several kinds of lubricants during sliding was measured. It is concluded that the lubricant is decomposed and hydrogen is generated through a catalytic reaction with the fresh steel surface. The amount of hydrogen generated from each lubricant depends on its lubricity, not on its chemical structure. It is also confirmed that the lubricant with the larger wear brings more generated hydrogen into steel. Based on the above mechanism of hydrogen generation, methods of inhibiting hydrogen brittle flaking with additives were investigated. It is clarified that the addition of corrosion inhibitors that form a passive state film on the steel surface effectively inhibits generation of hydrogen from lubricants and penetration of hydrogen into steel. Presented at the STLE Annual Meeting in Las Vegas, Nevada May 15-19, 2005 Review led by Lois Gschwender

Mechanisms of hydrogen generation during the mechanochemical treatment of biotite within D2O media

The mechanism of hydrogen generation during the mechanochemical treatment of biotite was examined by grinding experiments using a ball mil in H2O or D2O as a grinding media. From the linear relationship between the amount of generated hydrogen and the increase of the surface area of ground powders, the hydrogen productivity of biotite is estimated to be 0.036 μmol/m2, which agrees with the previous results in spite of the difference in the grinding conditions. D2 analyses by a mass spectrometry indicate that the produced amount of D2 accounts for only 10% of the total hydrogen and that more than 90% of hydrogen takes a form of a mixture of HD and H2. The observed isotope distribution clearly indicates that hydroxyls within the crystal structure can be a major source for the generation of hydrogen. Hydrogen generation originated from hydroxyls may indicate the higher hydrogen productivity of phyllosilicates than those of quartz and alkali feldspar.