Non-noble metallic Cu with three different roles in a Cu doped ZnO/Cu/g-C3N4 heterostructure for enhanced Z-scheme photocatalytic activity

Abstract

Doping, co-catalyst, and Z-scheme configuration are three potential approaches to enhance the photocatalytic activity of metal oxides. Herein, a Cu doped ZnO/Cu/g-C₃N₄ heterostructure is prepared using the calcination-hydrothermal method. The successful fabrication is confirmed using different analytical techniques. XRD and XPS analyses reveal the presence of Cu in two chemical states, Cu²⁺ and Cu⁰. Cu plays three roles in the Cu doped ZnO/Cu/g-C₃N₄ photocatalyst, as a dopant reducing the bandgap of ZnO, as an electron mediator facilitating the Z-scheme charge transport pathway, and as a co-catalyst enhancing the catalytic activity. Therefore, the Cu doped ZnO/Cu/g-C₃N₄ heterostructure exhibits higher photocatalytic activity than the single and binary photocatalysts. The optimized heterostructure degrades 99% of RhB and 98% of MB after 60 and 20 min respectively sunlight irradiation. Scavenger and photoluminescence experiments are used to investigate the charge separation, Z-scheme configuration, and main active species. LC-MS is employed to explore the Rh B pathway degradation. This work opens a new pathway for the investigation of the multiple roles of nonnoble metals in enhancing the photocatalytic activity.