Synthesis and Photocatalytic Properties of Single Crystalline (Ga1-xZnx)(N1-xOx) Nanotubes

• Published in: Israel journal of chemistry 2012-12, Vol.52 (11-12), p.1111-1117
• Main Authors: Hahn, Christopher, Fardy, Melissa A., Nguyen, Catherine, Natera-Comte, Michelle, Andrews, Sean C., Yang, Peidong
• Format: Article
• Language: English
• Subjects: alloy; Aqueous solutions; nanotube; oxynitride; photocatalyst; Solar energy; water splitting
• ISSN: 0021-2148; 1869-5868
• DOI: 10.1002/ijch.201200067

Recently, (Ga1‐xZnx)(N1‐xOx) 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 (Ga1‐xZnx)(N1‐xOx) 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 (Ga1‐xZnx)(N1‐xOx) nanotubes (x=0.05–0.10) with similar composition powders. Cocatalyst decorated samples were dispersed in aqueous solutions of CH3OH and AgO2CCH3 to monitor the H+ reduction and H2O 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.