A self-stable plasmonic Ag/p-Ag2O/n-BiOCl heterojunction with enhanced photocatalytic CO2 reduction

A series of Ag/Ag2O/BiOCl photocatalysts were prepared by chemically reducing Ag/Ag2O, and loaded it onto BiOCl with the creation of oxygen vacancies. The composite photocatalysts have greatly improved the CO2 photoreduction efficiency. Among them, the yields of 4% Ag/Ag2O loaded BiOCl for CO and CH4 could reach 30.7 μmol∙g−1∙h−1 and 16.0 μmol∙g−1∙h−1 (under simulated sunlight irradiation), 10.8 μmol∙g−1∙h−1 and 1.8 μmol∙g−1∙h−1 (under visible light irradiation), respectively. These yields are 4.7 and 5.3 times, 6.9 and 5.4 times higher than that of pure BiOCl (CO: 6.6 μmol∙g−1∙h−1, CH4: 3.0 μmol∙g−1∙h−1 under simulated sunlight irradiation, CO: 1.6 μmol∙g−1∙h−1, CH4: 0.3 μmol∙g−1∙h−1 under visible light irradiation, respectively). Ag0 exhibits the surface plasmon resonance (SPR) effect, thereby enabling efficient absorption of visible light and subsequent generation of high-energy hot electrons. Ag0 not only enhances the visible light response of photocatalysts, but the generated hot electrons by Ag0 can also actively participate in CO2 reduction reactions. In addition, the formation of Ag2O/BiOCl p-n heterojunction can promote the separation of photogenerated carriers while maintaining the overall redox ability of the semiconductor, leading to a significant improvement in photocatalyst efficiency. Furthermore, the Ag/Ag2O structure is exceptionally self-stable due to mutual electron transport, thereby improving the overall photocatalytic stability of the samples. Density functional theory (DFT) calculations elucidate the formation of the system's ohmic contact and p-n heterojunction. This study provides valuable insights into the significant potential of Ag/Ag2O/BiOCl composite photocatalysts for CO2 photocatalytic reduction.