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Hydrogen Generation (hydrogen + generation)

Distribution by Scientific Domains

Chemistry	47%
Polymers and Materials Science	23%

Distribution within Chemistry

Chemical Engineering	36%

Selected Abstracts

Photoelectrochemical Study of Nanostructured ZnO Thin Films for Hydrogen Generation from Water Splitting

ADVANCED FUNCTIONAL MATERIALS, Issue 12 2009
Abraham Wolcott
Abstract Photoelectrochemical cells based on traditional and nanostructured ZnO thin films are investigated for hydrogen generation from water splitting. The ZnO thin films are fabricated using three different deposition geometries: normal pulsed laser deposition, pulsed laser oblique-angle deposition, and electron-beam glancing-angle deposition. The nanostructured films are characterized by scanning electron microscopy, X-ray diffraction, UV-vis spectroscopy and photoelectrochemical techniques. Normal pulsed laser deposition produces dense thin films with ca. 200,nm grain sizes, while oblique-angle deposition produces nanoplatelets with a fishscale morphology and individual features measuring ca. 900 by 450,nm on average. In contrast, glancing-angle deposition generates a highly porous, interconnected network of spherical nanoparticles of 15,40,nm diameter. Mott-Schottky plots show the flat band potential of pulsed laser deposition, oblique-angle deposition, and glancing-angle deposition samples to be ,0.29, ,0.28 and +0.20,V, respectively. Generation of photocurrent is observed at anodic potentials and no limiting photocurrents were observed with applied potentials up to 1.3,V for all photoelectrochemical cells. The effective photon-to-hydrogen efficiency is found to be 0.1%, 0.2% and 0.6% for pulsed laser deposition, oblique-angle deposition and glancing-angle deposition samples, respectively. The photoelectrochemical properties of the three types of films are understood to be a function of porosity, crystal defect concentration, charge transport properties and space charge layer characteristics. [source]

Continuous Hydrogen Generation from Formic Acid: Highly Active and Stable Ruthenium Catalysts

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009
Albert Boddien
Abstract The ruthenium-catalyzed decomposition of formic acid was investigated with respect to continuous hydrogen generation and long-term stability of the catalytic systems. A highly active and stable system is presented, which was studied in batch and continuous modes for up to two months. The optimized catalyst system containing N,N -dimethyl- n -hexylamine with an in situ generated catalyst from (benzene)ruthenium dichloride dimer [RuCl2(benzene)]2 and 6 equivalents of 1,2-bis(diphenylphosphino)ethane (dppe) reached at room temperature a total turnover number (TON) of approximatly 260,000 with average turnover frequency (TOF) of about 900,h,1. Only hydrogen and carbon dioxide were detected in the produced gas mixture which makes this system applicable for direct use in fuel cells. [source]

Role of Modification Agent Coverage in Hydrogen Generation by the Reaction of Al with Water

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2010
Zhen-Yan Deng
Previous works indicated that Al particle surfaces could be modified by fine ,-Al2O3 grains, which can be used as a hydrogen-generation material, where the fine ,-Al2O3 grains were produced by the decomposition of the Al(OH)3 phase in the mixture. In this work, commercially available ,-Al2O3 powder was directly used as the modification agent and mixed with Al powder and heat treated at an elevated temperature. It was found that the modified Al powder produced by directly using ,-Al2O3 has an obvious shorter time for complete hydrogen generation than that using Al(OH)3 -produced ,-Al2O3. Microstructure analyses revealed that directly using ,-Al2O3 powder has a better coverage of fine ,-Al2O3 grains on Al particle surfaces than the Al(OH)3 -produced ,-Al2O3. This implies that a uniform distribution of modification agents on Al particle surfaces is an important factor for the Al,water reaction dynamics. [source]

ChemInform Abstract: Co,Co2B, Ni,Ni3B and Co,Ni,B Nanocomposites Catalyzed Ammonia,Borane Methanolysis for Hydrogen Generation.

CHEMINFORM, Issue 16 2009
Suresh Babu Kalidindi
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Hydrogen Generation at Ambient Conditions: Application in Fuel Cells

CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 8-9 2008
Albert Boddien
Abstract The efficient generation of hydrogen from formic acid/amine adducts at ambient temperature is demonstrated. The highest catalytic activity (TOF up to 3630,h,1after 20,min) was observed in the presence of in situ generated ruthenium phosphine catalysts. Compared to the previously known methods to generate hydrogen from liquid feedstocks, the systems presented here can be operated at room temperature without the need for any high-temperature reforming processes, and the hydrogen produced can then be directly used in fuel cells. A variety of Ru precursors and phosphine ligands were investigated for the decomposition of formic acid/amine adducts. These catalytic systems are particularly interesting for the generation of H2 for new applications in portable electric devices. [source]

Hydrogen generation in a reverse-flow microreactor: 1.

AICHE JOURNAL, Issue 8 2005
Model formulation, scaling
Abstract A 1-D model for methane partial oxidation in a tubular microreactor is considered. This work is motivated by a recent report by Kikas et al. that experimentally demonstrated the possibility of autothermal generation of hydrogen by partial oxidation of methane in a tubular microreactor. The reactor consists of four cylindrical channels, each 500 microns in diameter, containing Pt/13%,Rh catalyst. Autothermal generation of hydrogen was possible in both unidirectional (UD) and reverse-flow (RF) operations of the reactor, with the RF operation providing better hydrogen yield and lower temperatures than those of the UD operation. Critical comparison of methane oxidation and reforming kinetics from the literature is performed. An analysis of the timescales of individual processes within the reactor is presented to gain fundamental insight into the reactor operation. Finally, the effect of radiation heat transfer is also considered, and it is found to play an important role for a shorter-size reactor. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source]

Hydrogen generation from photoelectrochemical water splitting based on nanomaterials

LASER & PHOTONICS REVIEWS, Issue 4 2010
Y. Li
Abstract Hydrogen is potentially one of the most attractive and environmentally friendly fuels for energy applications. Safe and efficient generation, storage, and utilization of hydrogen present major challenges in its widespread use. Hydrogen generation from water splitting represents a holy grail in energy science and technology, as water is the most abundant hydrogen source on the Earth. Among different methods, hydrogen generation from photoelectrochemical (PEC) water splitting using semiconductors as photoelectrodes is one of the most scalable and cost-effective approaches. Compared to bulk materials, nanostructured semiconductors offer potential advantages in PEC application due to their large surface area and size-dependent properties, such as increased absorption coefficient, increased band-gap energy, and reduced carrier-scattering rate. This article provides a brief overview of some recent research activities in the area of hydrogen generation from PEC water splitting based on nanostructured semiconductor materials, with a particular emphasis on metal oxides. Both scientific and technical issues are critically analyzed and reviewed. [source]

Photoelectrochemical Study of Nanostructured ZnO Thin Films for Hydrogen Generation from Water Splitting

A closed-loop proposal for hydrogen generation using steel waste and a prototype solar concentrator

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2009
Abdul-Majeed Azad
Abstract An economically viable and environmental-friendly method of generating PEM grade hydrogen has been proposed and is by the reaction of certain metals with steam, appropriately called ,metal,steam reforming',MSR. The drawbacks of conventional processes (hydrogen and carbothermic reduction schemes) are overcome by resorting to solution-based reduction schemes and are made economically feasible using iron oxides from steel industry's mill-scale waste. A novel aqueous-based room temperature technique using sodium borohydride (NaBH4) as the reducing agent has been developed that produces highly active nanoscale iron particles (,40,nm). By using hydrazine as an inexpensive and, compared with NaBH4, more stable reductant, body centered cubic iron particles with ,5,nm edges were obtained via solvothermal process under mild conditions from acid digested mill-scale waste. The nanoscale zerovalent iron (nZVI) powder showed improved kinetics and greater propensity for hydrogen generation than the coarser microscale iron. The rate constants for the MSR were obtained for all the reduction schemes employed in this work and are given by khydrogen=0.0158,min,1kcarbon=0.0248,min,1ksodiumborohydride=0.0521,min,1 and khydrazine=0.1454,min,1, assuming first order kinetics. Another innovative effort converted the magnetite waste directly into nZVI under solvothermal conditions, thus obviating the sluggish and time-consuming acid dissolution step. This particular aspect has significant ramification in terms of time and cost of making the iron precursor. To initiate and sustain the somewhat endothermic MSR process, a solar concentrator consisting of a convex polyacrylic bowl with reflective aluminum coating was fabricated and evaluated. This unique combination of mill-scale waste as iron source, hydrazine as reductant, mild process conditions and solar energy as the MSR actuator obviates several drawbacks plaguing the grand scheme of producing and delivering pure and humidified H2 to a PEMFC stack. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Continuous Hydrogen Generation from Formic Acid: Highly Active and Stable Ruthenium Catalysts

Porous anodic alumina microreactors for production of hydrogen from ammonia

AICHE JOURNAL, Issue 4 2004
Jason C. Ganley
Abstract The synthesis and properties are described of a ruthenium-impregnated anodic aluminum catalyst for use in microreactors for the production of hydrogen from an ammonia feed. The catalyst structure was synthesized using microelectric discharge machining to create a series of 300 × 300-,m posts on an aluminum substrate. The posts were anodized to yield a 60-,m covering of anodic alumina, with an average surface area of 16 m2/gm and an average pore size of 50 nm. Ruthenium metal was dispersed on the alumina using conventional wet impregnation. A 0.9 × 0.9-cm reactor containing 250 posts decomposed 95% of anhydrous ammonia at 650°C to yield 15 sccm of hydrogen. A possible application of these microreactor fabrication methods is hydrogen generation for fuel cells in mobile power production. 2004 American Institute of Chemical Engineers AIChE J, 50:829,834, 2004 [source]

Role of Modification Agent Coverage in Hydrogen Generation by the Reaction of Al with Water

Hydrogen generation from photoelectrochemical water splitting based on nanomaterials

Hydrogen Economy Options for Australia

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5-6 2004
B. Mclellan
Global concerns over the effects of current carbon dioxide (CO2) emissions have lead to extensive research on the use of hydrogen as a potential energy carrier for a lower emissions society. Hydrogen can be produced from both fossil and renewable energy sources. The hydrogen economy, in which hydrogen will be a carrier of energy from renewable sources, is a long-term development and any increasing demand for hydrogen will probably be covered initially from fossil sources. Technologies for hydrogen generation from renewable energies are being explored, whereas technologies for hydrogen production from fossil fuels have to a certain extent reached maturity. This paper addresses the major hydrogen generation processes and utilisation technology (fuel cells) currently available for the move from a fossil fuelsbased economy to a hydrogen economy. In particular, it illustrates the applicability of different hydrogen sources using Australia as an example. [source]

Photoelectron Generation by Photosystem,II Core Complexes Tethered to Gold Surfaces

CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 4 2010
Michele Vittadello, Prof.
Abstract By using a nondestructive, ultrasensitive, fluorescence kinetic technique, we measure in,situ the photochemical energy conversion efficiency and electron transfer kinetics on the acceptor side of histidine-tagged photosystem,II core complexes tethered to gold surfaces. Atomic force microscopy images coupled with Rutherford backscattering spectroscopy measurements further allow us to assess the quality, number of layers, and surface density of the reaction center films. Based on these measurements, we calculate that the theoretical photoelectronic current density available for an ideal monolayer of core complexes is 43,,A,cm,2 at a photon flux density of 2000,,mol,quanta,m,2,s,1 between 365 and 750,nm. While this current density is approximately two orders of magnitude lower than the best organic photovoltaic cells (for an equivalent area), it provides an indication for future improvement strategies. The efficiency could be improved by increasing the optical cross section, by tuning the electron transfer physics between the core complexes and the metal surface, and by developing a multilayer structure, thereby making biomimetic photoelectron devices for hydrogen generation and chemical sensing more viable. [source]