Oxygen Vacancy-Driven Asymmetrical Charge Distribution on Bi-O-Sn Sites in Sn-Doped Bi2MoO6 for Efficient Photocatalytic CO2-to-CH4 Conversion

Abstract

Efficient proton-coupled electron transfer (PCET) at tailored active sites is beneficial for photocatalytic CO2 reduction, yet the relationship between catalytic sites and performance remains unclear. Herein, p-block Sn is introduced into the Bi2MoO6 lattice (Sn-BMO) via Bi site substitution to construct a novel oxygen vacancy (Ov)-Bi-O-Sn structure, where high-valence Sn induces Ov formation by lowering the Bi valence state, thereby creating a charge-asymmetrical region. This unique configuration promotes PCET: Sn acts as H2O oxidation site, enabling proton transfer to proximal Bi site connected to Ov that preferentially traps electrons to convert CO2. Furthermore, the electronic structure of Bi is modified to optimize Bi 6p-C 2p hybridization for formation of the key intermediate *CHO with low energy barrier. Consequently, Sn-BMO exhibits a remarkable CH4 evolution rate of 207.3 µmol g−1 h−1 with 95.7% CH4 selectivity in pure water, achieving a record apparent quantum efficiency of 9.4% at 420 nm. This work provides a novel approach to design charge-asymmetrical active site in multisite catalysts, elucidating how p-block elements influence catalytic performance in CO2 photoreduction.