Unveiling the Oxidation Processes of Pt3Ni(111) by Real-Time Surface Core-Level Spectroscopy

Pt3Ni(111) is the most efficient catalyst for the oxygen reduction reaction. Herein, we investigated the oxidation process of Pt3Ni(111) by time-resolved X-ray photoemission spectroscopy experiments with synchrotron radiation. For O-2 exposure at room temperature, two well-distinct O species are present with a sticking coefficient of 0.23-0.24 in the temperature range of interest for fuel-cell technology. We show that the Pt skin of Pt3Ni(111) is selectively replaced by Ni2O3 and NiO surface-skin layers upon heating in an O-2 environment at 700 and 900K, respectively. By dosing with O atoms, the formation of PtO is possible at 293K, whereas Ni2O3 is formed at 353K.