Spontaneous CVD growth of InxGa1-xN/GaN core/shell nanowires for photocatalytic hydrogen generation

Abstract

InxGa1-xN nanowires (NWs) have drawn great attentions as a promising photocatalyst for H2 generation via solar water splitting. In this article, m-axial NWs with InxGa1-xN/GaN core/shell structure can be formed spontaneously on the n-type Si (111) substrate via Ni-assisted chemical vapor deposition (CVD) method. CVD growth conditions were adjusted by tuning the duration and pressure. The microstructures, surface chemistry, and optical properties of the obtained NWs were characterized using various techniques. The growth mechanism is identified as a two-step process. The InxGa1-xN cores with a high density of basal stacking faults were grown by a vapour-liquid-solid (VLS) mode, while the GaN shells were grown on the sidewalls of InxGa1-xN core through a vapor-solid (VS) mode. The photocatalytic activities of the NWs were evaluated by the amount of H2 generated from water splitting. A thicker GaN shell was revealed to decrease the photoactivity by hindering the charge separation and transfer of electron-hole pairs generated inside the InxGa1-xN cores. A strategy can be proposed to improve the photocatalytic performance of NWs by terminating the VS growth of the GaN shells during the CVD process.