High-performance ZnS/GaN heterostructure photoanode for photoelectrochemical water splitting applications

We present a study of ZnS/GaN heterostructure photoanodes fabricated by using ZnS thin films deposited on GaN by atomic layer deposition and a significantly enhanced photoelectrochemical (PEC) water splitting performance was demonstrated. The PEC performance of the photoanodes was investigated for various ZnS thicknesses and GaN doping concentrations. The photocurrent density of the ZnS/GaN photoanode at zero bias was enhanced by a factor of 1.75 compared to that for the reference GaN structure. Furthermore, significantly enhanced photoanode stability was observed with the optimized ZnS coating. The high performance of the ZnS/GaN photoanode is attributed to the type-II band alignment of the heterojunction, which forms a potential barrier for electron injection to the electrolyte while facilitating hole transfer. Therefore, using a ZnS cocatalyst coated on GaN is a promising technique to fabricate photoanodes for PEC-based solar energy harvesting.