Direct water photoelectrolysis with patterned n-GaN

Direct photoelectrolysis of water was observed using a structured n-GaN photoanode, aqueous NaOH solution, and platinum cathode. The structured n-GaN was formed by selective area regrowth using metal stripes defined by photolithography. Gas evolution from both the n-GaN anode and the platinum cathode was observed under UV irradiation without external bias. The metal stripes eliminated current crowding and the n-GaN regrowth increased specific surface area. As a result, distinct improvements in photocurrent were achieved. The origin of the photocurrent and the conversion efficiency are discussed based on water-splitting reactions and etching reactions.