Plasmonic Au-decorated hierarchical p-NiO/n-ZnO heterostructure arrays for enhanced photoelectrochemical water splitting

Abstract

Photoelectrochemical (PEC) water splitting is one of most effective ways for converting solar energy into chemical energy. Single-component semiconductor structures as photoanodes always suffer from poor ability to capture photons and serious recombination of electron-hole pairs, which pose inferior photocurrent performance. In order to increase the photocurrent density, here, a hierarchical heterostructure of p-NiO/n-ZnO decorated with Au nanoparticles (NPs) was designed and prepared as photoanodes. Specifically, a n-ZnO nanorods@nanodisks (NRs@NDs) constructure was completely coated with a thin p-NiO layer to construct a miniature p-n junction arrays, and plasmonic Au NPs were attached on the surface of the thin p-NiO layer. Benefiting from such p-n heterostructure, p-NiO/n-ZnO NRs@NDs heterojunction arrays exhibited excellent rectifying behaviour for their I–V and semi-log I–V curves. Moreover, the photoanode of p-NiO/n-ZnO NRs@NDs had a lower emission intensity than that of n-ZnO NRs@NDs, which indicated the effective inhibition of electron-hole pairs recombination. More importantly, the photocurrent density of Au/p-NiO/n-ZnO NRs@NDs was measured to be as high as 1.78 mA cm −2 , outperforming that of pure n-ZnO NRs@NDs (0.61 mA cm −2 ). This method provides a green, and highly efficient photoanode for the PEC water splitting. • A micro p-NiO/n-ZnO NRs@NDs heterostructure decorated with plasmonic Au NPs was prepared. • p-NiO/n-ZnO NRs@NDs heterojunction arrays exhibited excellent rectifying behaviour. • The synergetic effect of inner electric field of p-n junctions and plasmonic Au effectively inhibit charge recombination. • The photocurrent density increased by approximately 2.9-fold compared to that of pure n-ZnO NRs@NDs.