Unbiased solar water splitting of GaN photoanodes with Au nanoparticles supported by plasmon-assisted hot-carrier transfer

Photoelectrochemical (PEC) water splitting is a reliable method for converting abundant solar energy into chemical energy. Thus far, the reported efficiencies for the energy conversion of solar to hydrogen (STH) do not meet the criterion for commercial use. A significant improvement in efficiency could be achieved by designing heterostructures, changing the size and shape of gold nanoparticles (Au NPs) and improving the crystal quality of materials used for PEC water splitting. In this study, we synthesized a noble metal/semiconductor composite photoanode by depositing Au NPs on gallium nitride (GaN). Under unbiased conditions, the Au NP/GaN composite photoanode exhibited an 11.4% enhancement in photocurrent density compared to pristine GaN. In addition, the STH conversion efficiency was increased to 1.14% and the incident photon-to-current conversion efficiency reached 67%. These achieved improvements are attributed to efficient light harvesting, effective Au NP/GaN interface for the extraction of hot electrons from Au NPs, and efficient charge-carrier-collection efficiency of the GaN photoelectrode.