Effect of KOH-Treatment at Sol-Gel Derived NiOx Film on GaN Photoanodes in Hydrogen Generation

Robust sunlight-driven water splitting is considered a well-known sustainable hydrogen generation technique. The selection of semiconductors for photoelectrodes is an essential aspect of the PEC reaction. GaN-based semiconductors have drawn considerable attention because of their tunable bandgaps and suitable band edge positions. In recent years, few articles have reported improvement strategies of water-splitting efficiency using GaN photoelectrodes, and most of the techniques are related to catalyst doping. Unfortunately, the most common cases suffer from loss of conductance, intense recombination effects, and photo-corrosions. In this article, an alkali-treatment process on NiOx-coated n-GaN was presented to enhance the efficiency of water-splitting kinetics and alleviate photocorrosions. Photoelectrode analyses revealed that on the NiOx/n-GaN surface, a conformal thin surface grafted with a hydroxyl (-OH) group in the NiOx films prepared by a sol-gel process was developed. Under illumination and dark conditions, the current-voltage curves indicated that the NiOOH formed in the alkali-treated NiOx film worked like an electrocatalyst to promote carrier transporting kinetics on GaN photoanodes. As a result, photocurrent density increased from 0.62 mA cm(-2) (n-GaN) to 1.21 mA cm-2 (NiO/n-GaN-KOH) at 1 V with an appreciable H-2 production rate (17.5 mu Mole cm(-2) h(-1)).

Automated summary

This article discusses a new method to improve the water-splitting efficiency of gallium nitride photoelectrodes using alkali-treated NiOx films. The study shows that NiOOH formed on the NiOx/n-GaN surface can act as an electrocatalyst to promote carrier transportation kinetics on GaN photoanodes. By using this method, the photocurrent density is increased, and a significant H-2 production rate is achieved.