Photoluminescence and Photocatalysis of Gallium Oxynitride Synthesized from Nitridation of Ga2O3

This paper reports the synthesis of a gallium oxynitride photocatalyst formed by nitridation of a wide-bandgap Ga2O3 under NH3 atmosphere at 800°C for 15 h. The gallium oxynitride catalyst has a bandgap energy of 2.1 eV, exhibiting photocatalytic activity for H2 and O2 evolution from aqueous methanol and silver nitrate solutions under visible light illumination. The crystalline structure and oxidation state of gallium oxynitride were characterized using X-ray diffraction (XRD), X-ray absorption, and X-ray photoelectron spectroscopy (XAS and XPS). These results indicate that the gallium oxynitride photocatalyst has a hexagonal wurtzite-like structure similar to that of GaN. Elemental analysis also reveals that the visible-light-active gallium oxynitride catalyst has a composition of Ga0.71□0.29O0.21N0.79 (□ indicates cation vacancies), suggesting the presence of gallium vacancies, and shallow donors formed by the nonstoichiometric substitution of nitrogen for oxygen. These defect states act as radiative centers in photoluminescence and induce charge recombination in photocatalytic reaction.