Abstract
In this study, we used 1H-1,2,4-triazole as a nitrogen source to synthesize gallium nitride and gallium nitride/zinc oxide solid solution (GaN:ZnO) nanoparticles for photocatalytic water splitting and hydrogen production. By controlling the temperature of vacuum thermal treatment and the ratio and addition sequence of metal precursors, we synthesized GaN:ZnO with different zinc-to-gallium (Zn/Ga) molar ratio. The composition, structure and morphology of the nanomaterials were extensively characterized by a variety of methods and techniques. We found that the sequence of mixing the precursors is crucial for the formation of GaN:ZnO structure. In addition, all the GaN:ZnO nanomaterials contained residual carbon that bonded to nitrogen or oxygen atom and might thus form structural defects. We studied the photocatalytic activities under irradiation with 450 W Hg-Xe lamp. The sample containing GaN:ZnO with Zn/Ga = 0.28 after further 450 oC-calcination and Rh2-yCryO3 as a cocatalyst showed the highest hydrogen production rate (4.7 μmol h^-1g^-1) in methanol aqueous solution under visible-light irradiation (λ > 400 nm, 256 mW cm^-2). The GaN:ZnO with Zn/Ga = 0.53 showed the highest oxygen production rate (39.9 μmol h^-1g^-1) in silver nitrate aqueous solution under visible-light irradiation. The relative low photocatalytic efficiency of the thus prepared GaN:ZnO nanoparticles may be associated with the presence of residual carbon and structural defects which might serve as the recombination centers of photoexcited electrons and holes.