Selective Photocatalytic CO₂ Reduction Through Plasmonic Z-Scheme Ag-Bi₂O₃-ZnO Heterostructures

Combination of plasmonic noble metal with semiconductors offers a promising and potential solar energy harvesting and conversion route. Herein, plasmonic Z-scheme Ag-Bi₂O₃-ZnO (AgBZ) heterostructure is designed and synthesized via solution combustion and photo-deposition method. Metallic Ag nanoparticles (NPs) were deposited over Bi₂O₃-ZnO heterostructure; thus, they exhibit strong visible light absorption owing to surface plasmon resonance (SPR). The photocatalytic efficiency of the synthesized catalysts is investigated by the photocatalytic CO₂ reduction to fuels under simulated solar light irradiation. The present system has shown an outstanding photocatalytic CO₂ reduction and excellent selectivity of CO. The evolved rate of CO fuel, the amount of CO produced per unit time, over optimized Ag-Bi₂O₃-ZnO (3AgBZ) heterostructures was (96.74 μmol g⁻¹/h) which was approximately 12 times larger than that of Bi₂O₃-ZnO (0AgBZ) and 49-fold than the quantity of evolved CO fuels over pure ZnO photocatalyst. The percentage of evolved CO to CH₄ fuels over optimized Ag-Bi₂O₃-ZnO (3AgBZ) heterostructures was about 50 : 1compared to that of 2 : 3 over Bi₂O₃-ZnO (0AgBZ). The great improvement and the high selectivity would be ascribed to the synergistic effect of metallic surface plasmon resonance and the Z-scheme charges transfer system. This work would open a window to construct a single photocatalyst with different charge separation systems and excellent CO₂ reduction selectivity. Finally, the mechanism for the enhanced photocatalytic performance by the synergistic effect was described and discussed.