Pt3Cr(111) alloy effect on the reversible potential of OOH(ads) formation from O2(ads) relative to Pt(111)

A quantum mechanical study of O-2 and OOH adsorption on Pt(111) and on a Pt monolayer on Pt3Cr(111) is presented. The calculated adsorption energies are used to predict the reversible potential for 02 reduction to OOH(ads) on these surfaces. The resulting 0.43 V for Pt(111) and 0.49 V for the Pt skin on the Pt3Cr(111) are far from the 1.23 V reversible potential for the four-electron reduction to water. However OOH(ads) easily dissociates over Pt-n sites (n >= 2) to OH(ads) and O(ads), the latter forming with a reduction potential greater than 1.23 V and the resulting heat loss contributes to the overpotential in the four-electron reduction process.