Single-Step Fabrication of Visible-Light-Active ZnO-GaN:ZnO Branched Nanowire Array Photoanodes for Efficient Water Splitting

Designing an efficient photoanode for water splitting is a promising way to produce hydrogen fuel for a green and sustainable future. Herein, we reported a facile single-step fabrication of ZnO-GaN:ZnO three-dimensional branched nanowire (3D B-NW) arrays photoanode for efficient visible-light-driven solar water splitting. The ZnO-GaN:ZnO 3D B-NW arrays were synthesized through chemical vapor deposition route via simultaneous growth of ZnO 1D NW arrays followed by the diffusion of gallium (Ga) and nitrogen (N) vapors into pregrown ZnO 1D NW arrays. The ZnO-GaN:ZnO 3D B-NW arrays were highly crystalline, and branches extended in all possible directions along the 100 orientation. The 3D geometry of the as-constructed photoanode offers supreme light harvesting ability, visible-light response due to N-doping, and enhanced electrical conductivity as a consequence of Ga insertion. A type II energy band diagram was evaluated for photogenerated electron-hole transport. The 3D B-NW arrays of ZnO-GaN:ZnO photoanode yield remarkably higher J_PEC of 1.81 mA/cm² leading to 37.12% enhanced photocurrent over ZnO 1D NW arrays photoanode. This growth route will open a new avenue for synthesis of 3D B-NW arrays of other semiconductors to improve the efficiency of solar-powered devices.