Synthesis of NiGa2O4 Octahedron Nanocrystal with Exposed {111} Facets and Enhanced Efficiency of Photocatalytic Water Splitting

Abstract For the first time, octahedral NiGa 2 O 4 nanocrystals having reactive pH‐dependent {111} facets are synthesized through a facile hydrothermal route without using any template or organic surfactant. The {111} facets of octahedral NiGa 2 O 4 display clearly enhanced photocatalytic generation of hydrogen and oxygen from water splitting and good photocatalytic stability. Density functional calculations suggest that mixed statistically occupied Ga/Ni (fourfold‐ and sixfold‐coordinated Ga/Ni) are most likely to be exposed at the (111) surface of NiGa 2 O 4 , which is very favorable for enhancing the photocatalytic activities, and the photoelectrochemical properties show that the NiGa 2 O 4 octahedron displays a better photocurrent than NiGa 2 O 4 nanorods with the [100] growth direction. The transient photocurrent decay scan results demonstrate that the NiGa 2 O 4 octahedron exposed {111} facet electrode exhibits a transient decay time of 4 s, whereas this time is only 2 s for NiGa 2 O 4 nanorod electrodes with the [100] growth direction. This longer transient decay time indicates that the charge‐carrier recombination rate is lower in the NiGa 2 O 4 octahedron electrode, which will contribute to the enhancement of the photocatalytic activity. The present study also demonstrates that designing nanostructures with the appropriate morphology and surface structures is a feasible approach for enhancing the photoexcited charge‐transfer lifetime and developing highly active semiconductor photocatalysts.