Pt 3 Cr ( 111 ) Alloy Effect on the Reversible Potential of OOH(ads) Formation from O2(ads) relative to Pt(111)

A quantum mechanical study of O2 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 O2 reduction to OOH(ads) on these surfaces. The resulting 0.43V for Pt(111) and 0.49V for the Pt skin on the Pt3Cr(111) are far from the 1.23V reversible potential for the four-electron reduction to water. However, OOH(ads) easily dissociates over Ptn sites (n⩾2) to OH(ads) and O(ads), the latter forming with a reduction potential greater than 1.23V and the resulting heat loss contributes to the overpotential in the four-electron reduction process.