Improved efficiency and stability of GaN photoanode in photoelectrochemical water splitting by NiO cocatalyst

The NiO cocatalyst was deposited on a GaN photoanode to improve the water splitting efficiency and to stabilize the photoelectrolysis of the GaN photoanode without corrosion of the GaN layer. The photoanode performance was investigated for various NiO deposition conditions based on metal organic decomposition. The GaN photoanode with the optimized NiO morphology showed significantly improved efficiency and photocurrent stability during water splitting compared to the reference GaN. No corrosion was observed for the GaN photoanode combined with NiO, which confirmed that the enhanced stability was related to the suppressed GaN etching at the surface. The improved water splitting performance was attributed to the fast transport of photo-generated holes in the valence band from GaN to NiO and the efficient water reduction at the NiO/electrolyte interface.