Engineering PtFe/LiO2 Frontier Orbital Interaction in Li–O2 Batteries

Elucidating the structure-activity relationship between the electronic structure of catalytic active sites and oxygen evolution reaction (OER) activity at the orbital level is critical yet challenging in lithium-oxygen (Li-O₂) batteries. Herein, employing frontier molecular orbital theory, we designed a Pt-based catalyst as a model cathode to investigate the influence of frontier orbital interactions between the Pt d_z² orbital and the 5σ orbital of LiO₂ on the OER activity. Specifically, compared to the pure Pt catalyst, the d_z²-d_z² orbital coupling between low-electronegativity Fe and Pt in PtFe catalyst induces predominant electron transfer from Fe to the d_z² frontier orbital of Pt. As the Pt content in PtFe alloys increases progressively (from Pt₅₈Fe₄₂, Pt₆₇Fe₃₃ to Pt₇₆Fe₂₄), the electron population of the Pt 5d_z² orbital gradually decreases (1.92 for Pt₅₈Fe₄₂, 1.85 for Pt₆₇Fe₃₃, and 1.80 for Pt₇₆Fe₂₄). This leads to a gradual enhancement in the strength of interactions between the Pt d_z² orbital and the frontier orbitals of LiO₂, consequently resulting in a progressive decline in the OER catalytic activity. Establishing the correlating between the electron population in the d_z² frontier orbital and OER activity provides a descriptor for designing efficient electrocatalysts in Li-O₂ batteries.