Abstract
<jats:p>Constructing heterojunction photocatalysts with vacancy modification is a feasible strategy for efficient CO2 reduction. However, weak interface interactions and low carrier migration efficiency seriously hinder improvements in photocatalytic performance. Here, a Cs2CuBr4-x@AgBr core-shell heterojunction was prepared via an in-situ photo-assisted silver ion insertion method. The electronic structure and coordination environment of the Cs2CuBr4-x@AgBr heterojunction were investigated using hard X-ray absorption fine structure (XAFS) and density functional theory (DFT) calculations. As a result, cationic bromine vacancies induce electron delocalization, adjust the electronic density of neighboring atoms, and enhance the transfer efficiency of photogenerated electrons. Moreover, the Br(p)-Ag(d) bonds formed in the Cs2CuBr4-x@AgBr heterojunction precisely connect the valence band (VB) of Cs2CuBr4 and the conduction band (CB) of AgBr, minimizing the charge transfer distance. Therefore, Cs2CuBr4-x@AgBr exhibits a CO generation rate of 99.7 μmol‧g–1‧h–1, and the value increases by 19.1 times compared with pure Cs2CuBr4. This work provides important insights for the rational design of vacancy-modified heterojunctions at the atomic level.</jats:p>