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Nature of the Intermediate Binding Sites in Hydrogen Oxidation/Evolution over Pt in Alkaline and Acidic Media
Author(s) -
Ramaker David E.,
Roth Christina
Publication year - 2015
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201500111
Subject(s) - overpotential , chemistry , catalysis , desorption , delocalized electron , hydrogen , crystallite , absorption (acoustics) , absorption spectroscopy , xanes , inorganic chemistry , analytical chemistry (journal) , crystallography , spectroscopy , materials science , adsorption , electrode , electrochemistry , biochemistry , physics , organic chemistry , composite material , quantum mechanics , chromatography
The formation of overpotential deposited H (H opd ) on fuel‐cell catalysts [Pt/Vulcan carbon (VC) and PtRu/VC] is explored with X‐ray absorption spectroscopy taken under fuel‐cell operating conditions at the anode. The X‐ray absorption fine structure technique was used to obtain the catalysts structure and Δ μ X‐ray absorption near‐edge structure technique to simultaneously obtain adsorbate coverage. These results are compared with H opd coverages obtained from previously reported impedance and IR spectroscopic studies on single crystal Pt faces and polycrystalline Pt, and also with previously reported theoretical DFT results and gas‐phase temperature programmed desorption results. A rearrangement of H opd from the ontop sites at the corners/edges of nanoparticles to the delocalized threefold face sites at higher H opd coverage is found. A strong pH effect on the binding energy of the corner/edge ontop sites is shown, which accounts, in part, for the two orders of magnitude drop in hydrogen‐oxidation activity for Pt nanoparticles in alkaline environments compared with acidic environments.