Electrocatalysis in Li–O2 battery over single-atom catalyst based on g-C3N4 substrate

Abstract

The development of Li–O2 battery is severely hindered by the sluggish reaction kinetics of the oxygen electrode. Herein, we perform a first-principles study of single transition metal atom supported on g-C3N4 substrate (TM/g-C3N4) as potential single-atom catalyst (SAC) in Li–O2 batteries. Combined electronic analysis and thermodynamic calculations, the electrocatalytic mechanism of TM/g-C3N4 SACs in Li–O2 batteries is elucidated. Due to strong metal-substrate interactions, the TM atom is durably anchored at the unsaturated pyridine N site in the holey g-C3N4 substrate, thereby enabling long cycling stability of the oxygen electrode. Among the fifteen candidates studied, Ru/g-C3N4 SAC exhibits the lowest discharge and charge overpotentials. This behavior can be attributed to the synergistic effect of the moveable d electrons of Ru and electron-rich N coordinators, which results in significant interfacial charges, metallic electrical conductivity, and large spin magnetic moments of the RuN2 active center. This study provides in-depth atomic and electronic insights into the catalytic mechanism of TM/g-C3N4 SACs in Li-O2 batteries.