Hydrogen Electrocatalysis by Carbon Supported Pt and Pt Alloys: An In Situ X‐Ray Absorption Study

Abstract

In situ x‐ray absorption spectroscopy (XAS) in 1 M was used to examine the electronic and structural effects of hydrogen adsorption on carbon supported Pt (Pt/C) and Pt alloyed with first row transition metals (Cr, Mn, Fe, Co, and Ni). In the case of Pt/C, potential excursions from the double layer region (0.54 V vs. RHE) to 0.0 V caused significant changes in the XAS spectra whereas none was observed for the alloys. The and x‐ray absorption near edge structure indicated the generation of empty electronic states in the vicinity of the Fermi level due to adsorption of hydrogen, and the extended x‐ray absorption fine structure indicated an increase in the coordination number of the first Pt‐Pt shell from 9 to 11. The latter was attributed to a reversible surface restructuring process. Alloying of the Pt suppresses both the electronic and structural effects at 0.0 V. A comparison of the electrochemical kinetics for hydrogen oxidation by these electrocatalysts in a proton exchange membrane fuel cell indicated that alloying of the Pt had insignificant effects on the kinetics.