Hydride phase formation in carbon supported palladium nanoparticle electrodes investigated using in situ EXAFS and XRD

Rose, Abigail and Maniguet, Stephanie and Mathew, Rebecca J. and Slater, Claire and Yao, Jun and Russell, Andrea E. (2003) Hydride phase formation in carbon supported palladium nanoparticle electrodes investigated using in situ EXAFS and XRD. Physical Chemistry Chemical Physics, 15 (5). pp. 3220-3225. ISSN 1463-9076

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Full text URL: http://dx.doi.org/10.1039/b302956e

Abstract

n situ EXAFS (extended X-ray absorption. ne structure), in situ XRD (X-ray diffraction) and electrochemical studies have been used to investigate the palladium hydride phases of carbon supported palladium nanoparticles as a function of applied potential. Electrochemical investigations showed an increase in the hydrogen to palladium ratio with an increasingly negative potential. The H/Pd ratio could be divided into four distinct regions, which described the palladium hydride phase present; the alpha-phase, a mixture of the alpha- and beta-phases, the beta-phase, and a hyperstoichiometric region. The beta-hydride phase stoichiometry obtained from the electrochemical data corresponded to PdH. However, the composition obtained from the lattice expansions observed from the in situ EXAFS and XRD, 3.3% and 3.8%, correspond to compositions of PdH0.59 to PdH0.68. The excess hydrogen and hyperstoichiometric amounts found at more negative potentials are attributed to either spillover on to the carbon support or trapping and subsequent reoxidation of H-2 in the porous electrode structure.

Item Type:Article
Additional Information:n situ EXAFS (extended X-ray absorption. ne structure), in situ XRD (X-ray diffraction) and electrochemical studies have been used to investigate the palladium hydride phases of carbon supported palladium nanoparticles as a function of applied potential. Electrochemical investigations showed an increase in the hydrogen to palladium ratio with an increasingly negative potential. The H/Pd ratio could be divided into four distinct regions, which described the palladium hydride phase present; the alpha-phase, a mixture of the alpha- and beta-phases, the beta-phase, and a hyperstoichiometric region. The beta-hydride phase stoichiometry obtained from the electrochemical data corresponded to PdH. However, the composition obtained from the lattice expansions observed from the in situ EXAFS and XRD, 3.3% and 3.8%, correspond to compositions of PdH0.59 to PdH0.68. The excess hydrogen and hyperstoichiometric amounts found at more negative potentials are attributed to either spillover on to the carbon support or trapping and subsequent reoxidation of H-2 in the porous electrode structure.
Keywords:EXAFS, Fuel Cell
Subjects:F Physical Sciences > F200 Materials Science
F Physical Sciences > F170 Physical Chemistry
F Physical Sciences > F130 Structural Chemistry
F Physical Sciences > F180 Analytical Chemistry
Divisions:College of Science > School of Engineering
ID Code:5433
Deposited By: Jun Yao
Deposited On:07 May 2012 20:21
Last Modified:07 May 2012 20:21

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