p-State of surface oxygen for mediating the s-band center of a single-atomic Ag catalyst for enhanced catalytic property for the oxygen reduction reaction

Abstract

The search of excellent electrocatalysts for the two-electron O₂-reduction reaction (2e⁻ ORR) is of great importance for the green synthesis of H₂O₂. This study developed a computational framework using density functional theory (DFT) and ab initio molecular dynamic simulation (AIMD) to investigate the influence of acid electrolytes, particularly H coverage, on the s-band center of a single-atomic Ag catalyst, leading to improved catalytic selectivity for the ORR. Specially, the screened catalyst Ag@Ti₂C exhibited remarkable intrinsic performance for 2e⁻ ORR with an overpotential of only 0.06 V. In acidic electrolytes, Ag@Ti₂C selectively bound to O-containing and H species, forming Ag@Ti₂CO₂H_x. The introduction of O functional groups improved the electron delocalization, enhancing O₂–Ag interactions. Significantly, the surface O atom's p-band center exhibited a parabolic trend with the H coverage on Ag@Ti₂CO₂. Consequently, the catalyst exhibited an optimal overpotential of 0.08 V for 2e⁻ ORR at an H atom coverage of 22.2%. It was found that the surface O p-state played a crucial role in mediating the s-band center of the single-atomic Ag catalyst, significantly influencing its catalytic performance in the ORR.