Structure engineering of a core/shell Si@Ta3N5 heterojunction nanowires array for photoelectrochemical water oxidation

Abstract

Structure-tuned core/shell n-Si@n-Ta₃N₅ nanowires array heterojunction photoanodes were prepared on a wafer scale by electroless metal-assisted etching of an Si wafer, spin coating of a Ta(OC₂H₅)₅ sol precursor solution, and ammonia treatment to convert it to Ta₃N₅. The length of the Si NWs and the thickness of the Ta₃N₅ shell were critical variables to control the high photoelectrochemical water splitting performance of the photoanode. The photocurrent density of the optimum core/shell Si@Ta₃N₅ nanowires array was 2.5 times higher than that of the planar Si@Ta₃N₅ composite at 1.23 V_RHE under 1 sun illumination. The Ta₃N₅ nanoshell served as a protection layer to significantly improve the chemical stability of the Si photoelectrode, and acted as a component to form a heterojunction with Si to promote the transport and separation of photoexcited charge carriers.