Hydroxylation of Platinum Surface Oxides Induced by Water Vapor

With its high stability and well-tuned binding strength for adsorbates, platinum is an excellent catalyst for a wide range of reactions. In applications like car exhaust purification, the oxidation of hydrocarbons, and fuel cells, platinum is exposed to highly oxidizing conditions, which often leads to the formation of surface oxides. To reveal the structure of these surface oxides, the oxidation of Pt in O₂ has been widely studied. However, in most applications, H₂O is also an important or even dominant part of the reaction mixture. Here, we investigate the interaction of H₂O with Pt surface oxides using near-ambient-pressure X-ray photoelectron spectroscopy. We find that reversible hydroxylation readily occurs in H₂O/O₂ mixtures. Using time-resolved measurements, we show that O-OH exchange occurs on a time scale of seconds.