Engineering eg Orbital Occupancy of Pt with Au Alloying Enables Reversible Li-O2 Batteries.

Abstract

Constructing well-designed catalysts to accelerate OER catalytic activity and alleviate the charge overpotential is prevailing for achieving sophisticated Li-O2 batteries. Herein, we report a concept for engineering the eg occupancy of Pt with M alloying (M=Au, Ru) to tune the charge overpotentials for achieving high-performance Li-O2 batteries. The X-ray photoelectron spectroscopy results coupled with density functional theory (DFT) calculations reveal that the highly electronegative Au can capture more eg electrons from Pt, leading to less eg electrons of Pt in PtAu than that in PtRu. The lower eg occupancy of Pt atoms in PtAu alloys entails the upward shift of the Pt d band, which causes a strong binding strength towards the intermediates (LiO2 ), thereby decreasing the OER energy barrier. As a consequence, the Li-O2 battery with a PtAu cathode delivers a low charge overpotential of 0.36 V and superior cycle life of 220 cycles at a cutoff capacity of 1000 mAh g-1 , which is among the best in the reported noble metal-based cathodes.