A galvanic replacement reaction to synthesise metal/ZnO heterostructured films on zinc substrates for enhanced photocatalytic performance

Abstract

The construction of non-precious transition metal/ZnO heterostructured films is being considered as an effective way to promote photocatalytic efficiency for their practical applications. Herein, a general and facile approach is reported for the first time to synthesize a series of M/ZnO (M = Cu, Cd, Co) heterostructured films on Zn substrate based on a simple one-step galvanic replacement reaction between Zn substrate and metal salt solution under hydrothermal condition without the use of any other reactants or additives. Zn substrate functions as not only the reducing agent, but also the source of ZnO to simplify the recipes and facilitate the synthetic procedures. Among M/ZnO heterostructured films, due to their matching degree of phase and cell parameters, two kinds can be prepared, including Cu/ZnO and Co/ZnO heterostructures with metal nanoparticles (e.g. Cu and Co) anchored on ZnO nanorods and Cd/ZnO heterostructures assembled by Cd nanorod core and ZnO nanorod branches. A pine tree-like Cu/ZnO heterostructured film is chosen as a representative to demonstrate the facility and effectiveness of the strategy, which exhibits higher photocatalytic efficiency towards visible light irradiation than bare ZnO nanospindles. The enhanced photocatalytic activities may be mainly attributed to the surface plasmon absorption of Cu nanoparticles in the visible region, which increases the optical absorption of the Cu/ZnO heterostructures and promotes the transfer of photo-induced electrons from Cu nanoparticles into ZnO nanorods. This general method can be further explored to guide the design of metal/metal oxide heterostructured films on other substrates, such as Cu, Ni and Ti foils.