Effective photocatalytic water splitting enhancement using GaN/ZnO/NiO core/shell nanocolumns

In this study, the GaN/ZnO heterojunction and ZnO–NiO p–n junction core/shell nanocolumns were fabricated based on GaN nanocolumns. During the water splitting measurements, the photocurrent of GaN/ZnO/NiO (GZN) nanocolumns is 2.1 times higher than that of GaN nanocolumns. The enhancement is mainly due to the heterojunction between GaN and ZnO and the p–n junction between ZnO and NiO, which build strong built-in electric fields to accelerate the separation of photogenerated carriers. Besides, the refractive index of NiO and ZnO is smaller than that of GaN, which can facilitate the light absorption of GZN nanocolumns and improve the water splitting performance. Our work has greatly improved the photocatalytic efficiency of GaN for water splitting applications.