Synthesis and Photocatalytic Properties of Single Crystalline (Ga_1‐xZn_x)(N_1‐xO_x) Nanotubes

Abstract Recently, (Ga 1‐x Zn x )(N 1‐x O x ) has gained widespread attention as a comparatively high efficiency photocatalyst for visible‐light‐driven overall water splitting. Despite significant gains in efficiency over the past several years, a majority of the photogenerated carriers recombine within bulk powders. To improve the photocatalytic activity, we used an epitaxial casting method to synthesize single‐crystalline, high surface area (Ga 1‐x Zn x )(N 1‐x O x ) nanotubes with ZnO compositions up to x=0.10. Individual nanotubes showed improved homogeneity over powder samples due to a well defined epitaxial interface for ZnO diffusion into GaN. Absorption measurements showed that the ZnO incorporation shifts the absorption into the visible region with a tail out to 500 nm. Gas chromatography (GC) was used to compare the solar water splitting activity of (Ga 1‐x Zn x )(N 1‐x O x ) nanotubes (x=0.05–0.10) with similar composition powders. Cocatalyst decorated samples were dispersed in aqueous solutions of CH 3 OH and AgO 2 CCH 3 to monitor the H + reduction and H 2 O oxidation half reactions, respectively. The nanotubes were found to have approximately 1.5–2 times higher photocatalytic activity than similar composition powders for the rate limiting H + reduction half reaction. These results demonstrate that improvements in homogeneity and surface area using the nanotube geometry can enhance the photocatalytic activity of GaN:ZnO for solar water splitting.