Tunable thickness of mesoporous ZnO-coated metal nanoparticles for enhanced visible-light driven photoelectrochemical water splitting.

The insufficient utilization of sunlight of ZnO, due to its broad band gap, results in low efficiency for photocatalytic hydrogen production. In this work, plasmonic noble metal nanoparticles (NPs) with different shapes (spheres and rods) were combined with mesoporous ZnO forming core-shell nanostructure to enhance the photocatalytic efficiency of ZnO in visible-light region. The photoelectrochemical water splitting activities of the metal@ZnO core-shell nanocomposites (NCs) were investigated. The photocurrent response of metal@ZnO NCs was found higher than pure ZnO or the mixture of metal NPs and ZnO ascribed to the effective charge transfer mechanism. It was also found that the photocurrent of metal@ZnO NCs was related to the thickness of ZnO and there was optimized shell for each kind of metal cores. Moreover, the introduction of Ag shell can get a higher photoelectrocatalytic efficiency compared to pure Au NPs core due to lower Schottky barrier between Ag and ZnO and wider extinction range in the visible light of Au@Ag NPs.