Enhancing photocatalytic CO₂ reduction with Z-scheme heterojunction Ag/Bi₂MoO₆/BiOBr composite films: Synthesis and mechanistic insights

This study presents the successful synthesis of a novel Z-scheme heterojunction composite film consisting of Ag/Bi2MoO6/BiOBr through electrochemical processes and ion-exchange techniques, followed by the photodeposition of noble metal silver (Ag) onto the composite structure. The catalytic efficiency of semiconductor photocatalysts is greatly improved by utilizing the localized surface plasmon resonance (LSPR) effect observed in Ag nanoparticles (NPs). Furthermore, the noble metal Ag serves as an intermediary bridge facilitating charge transfer between Bi2MoO6 and BiOBr, while the formation of a Schottky barrier effectively inhibits the recombination of photo-generated electron-hole pairs. As a result, the Ag-deposited Bi2MoO6/BiOBr film exhibits superior photocatalytic performance in the reduction of CO2 compared to its unmodified counterpart. Our experimental results indicate a non-linear relationship between Ag deposition and the efficiency of photocatalytic CO2 reduction to CO, characterized by an initial increase in efficiency followed by a decline. The optimized 1.5%-Ag/Bi2MoO6/BiOBr film demonstrates exceptional photocatalytic activity, attaining a CO production rate of 13.65 μmol/(g·h). This research explores the fundamental mechanisms that lead to improved photocatalytic CO2 reduction capabilities of the Ag/Bi2MoO6/BiOBr film. Our research offers important perspectives for the thoughtful design and production of highly efficient photocatalysts, which are essential for advancing sustainable energy solutions.