Controllable Synthesis of Vapor-Liquid-Solid Grown GaN Nanowires for Photoelectrochemical Water Splitting Applications

Abstract

Vapor-liquid-solid (VLS) grown single crystalline GaN nanowire (NW) arrays of controllable aspect ratio and density were employed as the working photoanode for photoelectrochemical water splitting (PEC-WS) applications. The NW density of GaN NWs was controlled by tuning the different VLS growth parameters, while the aspect ratio was depending on the growth time. We observed a significant increase of the photocurrent with denser GaN NWs due to the enhanced light trapping effects; however, the PEC-WS process stability was degraded with time. Further increase of the photocurrent by about 34% at 1 Volt and a better time-dependent PEC-WS stability were achieved by increasing the aspect ratio of the GaN NWs due to the enhanced surface-to-volume ratio of the photoanode. The applied bias photon-to-current efficiency of the GaN NWs revealed a great shift of the optimal potential to lower values with enhanced NW lengths, indicating an interesting modification in the photoanode performance with increasing the aspect ratio of the GaN NWs.