Photoelectrochemical Property Differences between NiO Dots and Layer on n-Type GaN for Water Splitting

Abstract

The n-type GaN photoelectrode is suitable for hydrogen generation from water because it can split water without bias. However, the n-type GaN photoelectrode has the anodic corrosion problem caused by the etching of the GaN. This problem can be resolved by NiO loading on GaN. The reported method of NiO loading on GaN surface was carried out by coating the surface by diluted metal organic decomposition (MOD) and high-temperature annealing. Since no NiO loading methods using Ni(OH)2 dispersed solution and low-temperature annealing have been reported, in this study, we attempted NiO loading Ni(OH)2 dispersed solution. Experimental results confirmed that the method can be easily performed and effective. In addition, we also compared the photoelectrochemical properties of the n-type GaN samples obtain by Ni(OH)2 loaded using four different Ni(OH)2 synthetic methods, loading by NiO-MOD, and no-NiO loading. The photocurrent densities of all samples loaded using Ni(OH)2 dispersed solution increased compared to samples without NiO and with NiO-MOD. The photocurrent densities and stabilities were affected by the NiO shape and density which were found to be related with the method of synthesizing the Ni(OH)2 dispersed solutions. The effects of NiO shape and density on the photocurrent density and stability are also discussed.