Title

Factors controlling the energetics of the oxygen reduction reaction on the Pd-Co electro-catalysts: Insight from first principles

Authors

Authors

S. Zuluaga;S. Stolbov

Comments

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Abbreviated Journal Title

J. Chem. Phys.

Keywords

PLATINUM-MONOLAYER ELECTROCATALYSTS; PALLADIUM ALLOY ELECTROCATALYSTS; TRANSITION-METAL SURFACES; KINETIC-PARAMETERS; ACIDIC MEDIA; ADSORPTION; PT(111); ORIGIN; WATER; O-2; Physics, Atomic, Molecular & Chemical

Abstract

We report here results of our density functional theory based computational studies of the electronic structure of the Pd-Co alloy electrocatalysts and energetics of the oxygen reduction reaction (ORR) on their surfaces. The calculations have been performed for the (111) surfaces of pure Pd, Pd(0.75)Co(0.25) and Pd(0.5)Co(0.5) alloys, as well as of the surface segregated Pd/Pd(0.75)Co(0.25) alloy. We find the hybridization of dPd and dCo electronic states to be the main factor controlling the electrocatalytic properties of Pd/Pd(0.75)Co(0.25). Namely the dPd-dCo hybridization causes low energy shift of the surface Pd d-band with respect to that for Pd(111). This shift weakens chemical bonds between the ORR intermediates and the Pd/Pd(0.75)Co(0.25) surface, which is favorable for the reaction. Non-segregated Pd(0.75)Co(0.25) and Pd(0.5)Co(0.5) surfaces are found to be too reactive for ORR due to bonding of the intermediates to the surface Co atoms. Analysis of the ORR free energy diagrams, built for the Pd and Pd/Pd(0.75)Co(0.25), shows that the co-adsorption of the ORR intermediates and water changes the ORR energetics significantly and makes ORR more favorable. We find the onset ORR potential estimated for the configurations with the O-OH and OH-OH co-adsorption to be in very good agreement with experiment. The relevance of this finding to the real reaction environment is discussed. (C) 2011 American Institute of Physics. [doi:10.1063/1.3643714]

Journal Title

Journal of Chemical Physics

Volume

135

Issue/Number

13

Publication Date

1-1-2011

Document Type

Article

Language

English

First Page

10

WOS Identifier

WOS:000295625400059

ISSN

0021-9606

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