Ag-decorated ZnO-based nanocomposites for visible light-driven photocatalytic degradation: basic understanding and outlook

Heterogeneous photocatalytic processes have exhibited tremendous potential in the field of solar energy and environmental remediation. Next to TiO2, ZnO has been widely used as a promising photocatalyst material in recent years. However, several noticeable drawbacks make it less effective, such as poor solar-light harvesting and rapid recombination of photo-excited charge carriers. To overcome these drawbacks, the decoration of noble metal nanoparticles on ZnO surfaces is a feasible strategy due to its localized surface plasmon resonance absorption, which aggrandizes the visible absorption of ZnO. In addition, the formation of the Schottky barrier at the metal-semiconductor interface can effectively separate photo-induced charge carriers. Among theses noble metals, due to the high conductivity, antimicrobial activity, mechanical thermal strength, and electrical double layer capacitance of silver (Ag), Ag-decorated ZnO (ZnO/Ag) nano-photocatalysts have exhibited remarkable photocatalytic efficiency and high cost performance for the degradation of organic pollutants, endowing them with growing potential in applications. In this review, we focus on the recent advancements (including the fundamental degradation mechanisms, synthesis methods, corresponding applications, and optimized strategies ) in ZnO/Ag-based photocatalysts for visible light-driven photocatalytic degradation, and conclude with a perspective on the future direction and prospects for these types of nanocomposite photocatalysts.