Design strategy for CuO-ZnO S-scheme heterojunction photocatalysts in the presence of plasmonic Ag and insights into photoexcited carrier generation and interfacial transfer in diverse structural configurations of the heterostructure system

This work demonstrates an exploration of the dynamics of the photogenerated electrons and holes in the S -scheme heterojunctions of CuO nanoparticles and ZnO microrods in the presence of plasmonic Ag nanoparticles. Herein, n-type ZnO microrods developed by the cost-efficient thermal decomposition method are decorated with nanoparticles of CuO and Ag deposited by the direct current magnetron sputtering. Microstructural analyses based on XRD, FESEM, and FETEM measurements reveal interfaces of single crystalline wurtzite ZnO with phase pure CuO and polycrystalline Ag nanoparticles. XPS results complement microstructural information from the FETEM measurements, signifying plasmon loss features of Ag nanoparticles and suggest direct electron transfer from Ag to ZnO, where ZnO microrods constitute the major part of the photocatalysts. The plausible schemes of light collection, carrier generation, and transfer have been presented based on the structural and optical prop-erties, which are utilized to explain the photocatalytic degradation of aqueous cationic Rhodamine 6G under UV-Vis-NIR illumination. The optimized CuO-ZnO heterojunction is highly efficient as a photocatalyst with a degradation rate of 89% due to a greater light collection ability and S-scheme based electron-hole separation at multiple junctions. The plasmonic modulation of the photocatalytic activities of the heterojunction-heterostructure systems is critically governed by the structural organizations of the materials.