(45b) Evolution of the Pt (111) Surface Under the Presence of Oxygen, Chlorine and Hydronium Species

Pt is the most popular material used as a catalyst for the oxygen reduction reaction in proton-exchange membrane fuel cells. One important challenge in this technology is to improve the catalytic efficiency, and in this regard, one of the important aspects is to develop a thorough understanding of the changes that the catalyst surface experiences under the presence of the different species present during reaction. In this work, density functional theory was used to study the oxidation of the Pt (111) surface analyzing buckling and reconstruction effects on the top Pt layer and variation of the atomic charges at two different oxygen coverages: 0.50 and 0.5625 ML. Results show a direct relationship among the oxidation and the detachment of the Pt atoms from the surface. Additional simulations to analyze the influence of hydronium and chlorine species on the oxidation of the Pt atoms on the 0.5625 ML adsorbed O systems were performed. In most cases we observe proton transfer to the adsorbed O, whereas the chlorine species plays an additional oxidant role. These systems were studied at the fuel cell operation temperature of 80 oC using ab initio molecular dynamics methods.