Synergism of the Plasmonic Effect and Schottky Junction to Effectively Facilitate Photocatalytic CO₂ Reduction of Bi₄O₅I₂@Cu

To achieve highly efficient photocatalytic CO2 reduction, it is crucial to attain efficient light absorption across a wide spectral range and rapid separation of photogenerated electrons and holes. Herein, we synthesize a Bi4O5I2@Cu photocatalyst by the in situ photodeposition of Cu nanoparticles (NPs) onto Bi4O5I2 micron flowers (MFs) assembled from numerous nanosheets. The hierarchical hybrid of Bi4O5I2@Cu combines two distinct merits: the surface plasmon resonance (SPR) effect induced by Cu NPs and the Bi4O5I2/Cu Schottky junction. Specifically, the SPR effect of Cu NPs can broaden the range of light absorption to the near-infrared, resulting in the generation of hot electrons. Some of these hot electrons then migrate across the Schottky barrier of Bi4O5I2/Cu, injecting into the conduction band (CB) of Bi4O5I2 MFs. This process increases the electron density in the CB of Bi4O5I2, which is beneficial for the CO2 photoreduction. On the other hand, the Bi4O5I2/Cu Schottky heterojunction effectively prevents the electron backflow from Bi4O5I2 to Cu and facilitates the transfer of photogenerated holes in the valence band (VB) of Bi4O5I2 into Cu NPs for H2O oxidation, as supported by density functional theory (DFT) calculations, confirming the achievement of efficient spatial separation and migration of charge carriers. Under visible light irradiation without any sacrificial reagent, Bi4O5I2@Cu-0.5 with an optimal loading of Cu NPs demonstrates a significantly enhanced CO production rate of 7.34 mu mol g(-1) h(-1), which is approximately 13.1 times higher than that of the bare Bi4O5I2 MFs and also surpasses those of the most reported bismuth oxyhalide-based and plasmon-based photocatalysts. Therefore, this work offers a new strategy for the development of excellent photocatalysts by the synergistic utilization of the plasmonic effect and Schottky junction.