Details

Autor(en) / Beteiligte

• Ramaker, David E.
• Roth, Christina

Titel

Nature of the Intermediate Binding Sites in Hydrogen Oxidation/Evolution over Pt in Alkaline and Acidic Media

Ist Teil von

• ChemElectroChem, 2015-10, Vol.2 (10), p.1582-1594

Ort / Verlag

Weinheim: Wiley Subscription Services, Inc

Erscheinungsjahr

2015

Link zum Volltext

Quelle

Wiley Online Library - AutoHoldings Journals

Beschreibungen/Notizen

• The formation of overpotential deposited H (Hopd) 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 Δμ X‐ray absorption near‐edge structure technique to simultaneously obtain adsorbate coverage. These results are compared with Hopd 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 Hopd from the ontop sites at the corners/edges of nanoparticles to the delocalized threefold face sites at higher Hopd 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. What potential! Intermediate coverage during the hydrogen oxidation/evolution reaction is determined from the Δμ X‐ray absorption near‐edge structure at potentials above 0.0 V and from previously reported cyclic voltammetry impedance data at potentials below 0 V on Pt surfaces. A rearrangement of overpotential deposited hydrogen (Hopd) from the ontop sites at the corners/edges of nanoparticles (green; see figure) to the delocalized threefold face sites (red) at higher Hopd coverage is found.