Enhanced photoelectrochemical performance of cobalt phosphate modified GaN-ZnO Nanowires/GaN microrods heterostructure photoanode by vacancy defect modulation

Gallium-zinc oxynitride solid solution has been considered as a promising candidate material for photo-electrochemical (PEC) water splitting. However, its PEC performance is severely limited by the poor charge separation efficiency and the adverse intrinsic vacancy defects. Herein, to solve these problems, we developed a novel strategy for constructing dendritic (GaN)(1-x)(ZnO)(x)/GaN arrays with type-II heterojunction on a conductive GaN crystalline substrate by an Au-assisted chemical vapor deposition method. Then, an additional annealing treatment in Ar is carried out to further decrease the density of surface oxygen vacancy and to increase the density of O-N-V-Ga vacancy complexes for enhancing photoelectrochemical performance. Under the synergistic effect of type-II heterojunction and vacancy modulation, the optimized (GaN)(1-x)(ZnO)(x)/GaN photoanode exhibits a photocurrent density of 0.25 mA cm(-2) at 1.23 V vs. RHE and the surface modification with CoPi co-catalyst can further increase the photocurrent density to 0.45 mA cm(-2) at 1.23 V vs. RHE. It is demonstrated that the O-N-V-Ga vacancy complexes are beneficial to increase the PEC performance of gallium zinc oxynitrides.