Combined quantum chemistry and Monte Carlo simulation of competitive adsorption of O₂ and OH on Pt surfaces

Highlights: • Competitive adsorption of O₂ and OH on different Pt surfaces was theoretically studied. • The adsorption energies of O₂ and OH depend on the Pt surfaces and the adsorption sites. • The order of O₂ adsorption efficiency was characterized. - Abstract: To obtain a microscopic explanation on the difference of oxygen reduction reaction activity on different Pt low index surfaces, we simulated competitive adsorptions of O₂ and OH on four Pt low index surfaces. Firstly, all possible chemical adsorption configurations of the O₂ and OH molecules on the three surfaces were acquired through density functional theory. The distribution of these configurations on the different surfaces was collected from Monte Carlo simulations. Our results demonstrated that the adsorption energy order of O₂ on different surfaces was (110)(1 × 2) > (110) > (100) > (111) and that the adsorption energy order of the OH molecules on Pt surfaces was the same. Considering the competitive adsorption of O₂ and OH on Pt surfaces, the final O₂ adsorption efficiencies order of three surfaces was (111) > (110) > (100) > (110)(1 × 2), which was consistent with the experimental activities of oxygen reduction. Our study provided theoretical references for previous experimental studies and had important significance for the understanding of oxygen adsorption on Pt surfaces.