New insights into O and OH adsorption on the Pt-Co alloy surface: effects of Pt/Co ratios and structures.

In this study, the electronic structure and adsorption properties of O and OH for a series of Pt-Co alloys with different Pt/Co ratios (5 : 1, 2 : 1, 1 : 1, 1 : 2, and 1 : 5) were systematically studied using density functional theory calculations. Our computational results demonstrated that the introduced Co atoms have multiple effects on the surface electronic structure in different atomic layers of the alloy, leading to the discrepancies in the electronic structure between Pt-skin structures and non-Pt-skin structures. Moreover, the influence of the surface electronic structure on the adsorption of O and OH slightly differs. Indeed, the adsorption of O is more remarkably affected by the Pt/Co ratio than the OH adsorption and better follows the d-band center theory. Due to the difference of the alloy structure and the effect of different layer Co atoms, the adsorption of O and OH on the alloy configurations with the same Pt/Co ratio has different outcomes. Our results suggested that the oxygen reduction reaction (ORR) activity is related not only to the Pt/Co ratio of alloy surfaces but also to the specific surface structure. Our research can provide theoretical insights into the development of ORR catalysts.