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

Abstract

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/cm 2 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.

Inside‐and‐Out Semiconductor Engineering for CO2 Photoreduction: From Recent Advances to New Trends

“…Photocatalysts with 3D structure, such as nanosheets‐assembled flowers, [ 227–233 ] hollow spheres, [ 234–243 ] and hierarchical NW arrays, [ 244–252 ] have been widely developed. Due to their special features, including high specific surface area and high light utilization, they always demonstrate excellent photocatalytic CO 2 reduction performance.…”

Direct Synthesis of Oxynitride Nanowires through Atmospheric Pressure Chemical Vapor Deposition

“…Han and co-workers employed vacuum chemical vapor deposition (CVD) and ZnGa 2 O 4 nanoparticles as the source material for the synthesis of single crystal GaN:ZnO nanowires [ 16 ]. Modifications in epitaxial growth condition in recent years resulted in fabrication of oxynitride thin film [ 17 , 18 ], and 1-D heterostructures [ 19 , 20 ]. GaN:ZnO solid solution nanotubes were prepared through diffusion of the ZnO core into the GaN shell through epitaxial casting route [ 14 ].…”

Irradiation Direction‐Dependent Surface Charge Recombination in Hematite Thin‐Film Oxygen Evolution Photoanodes

“…Since the pioneering work of the TiO 2 photoanode for PEC water splitting by Fujishima and Honda in 1972, plenty of semiconductors have been reported to be active for PEC water splitting, including n‐type semiconductors like α‐Fe 2 O 3 , BiVO 4 , g‐C 3 N 4 , and WO 3 as photoanodes for oxygen evolution and p‐type semiconductors like Cu 2 O as photocathodes for hydrogen evolution. To improve the PEC performance of semiconductor photoelectrodes, many strategies such as hetero atom doping, construction of heterostructures, and deposition of electrocatalysts, have been proposed. Overall, the key to optimizing the PEC cell lies in efficient collection of charge carriers generated in the semiconductor photoelectrode under irradiation both at the semiconductor/substrate interface (SSI) and at the semiconductor/liquid junction (SCLJ) .…”