DFT Study for CO and H₂ Adsorption and Related Reactions on Pt alloy Electrode

Abstract

The density functional theory (DFT) calculation has been applied to investigate CO and H₂ adsorption onto Pt-Ru, Pt-Rh, Pt-Pd, Pt-Ag alloys as well as Pt metal modeled by Pt_xM_10−x (M = Ru, Rh, Pd, Ag, and x = 3, 5, 7) clusters. The most durable catalysts for CO poisoning were searched using the criteria that adsorption of CO should be weakened compared to pure Pt but adsorption of H₂ should not be weakened, or activation energy for the H-H bond fission is not increased. Pt₅Ru₅ and Pt₇Ru₃ were the best catalyst in conformity with many experimental works. Slab calculation showed that Pt is more localized in the surface layer than the bulk content in Pt-Ru alloy. Energy profiles calculated for the two reactions, CO + OH → COOH and H₂O → OH + H were compared between Pt and Pt-Ru alloy. No significant advantage for Pt-Ru alloy was found for the former reaction, but OH formation was more facile for the Ru site of Pt-Ru alloy.