Controlled Fabrication of α-GaOOH and α-Ga2O3 Self-Assembly and Its Superior Photocatalytic Activity

In this article, we report the fabrication of gallium oxide (alpha-Ga2O3) microspheres (GOMs) by a self-assembly process. Gallium nitrate with oxalic acid in a hydrothermal process results in alpha-GaOOH, which was further converted into gallium oxide by calcinations at 450 degrees C for 3 h. We first report the formation of various morphological alpha-GaOOH by using the above-mentioned methodology. The influence of hydrothermal temperature and time on the crystal structure and its morphology was studied, and the results indicated that hydrothermal temperature played an important role in the final morphology of alpha-GaOOH. The flower-like alpha-GaOOH formed at 175 degrees C is converted into rodlike alpha-Ga2O3 after calcination at 450 degrees C, and the alpha-GaOOH microsphere and microrod formed at 200 and 225 degrees C retained their morphology during the calcination process, respectively. The synthesized alpha-GaOOH and alpha-Ga2O3 were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), and nitrogen adsorption analysis. The XRD patterns indicated that well-crystallized alpha-GaOOH and alpha-Ga2O3 were formed in a hydrothermal and calcination process, respectively. The FE-SEM images indicated the formation of well-organized microspheres and rnicroflowers, which were composed of nanoparticles and nanoplates, respectively. The photocatalytic degradation of Acid Orange 7 (AO7) dye and Cr(VI) reduction by using the synthesized GOM under UV light irradiation was investigated. The photocatalytic experiment showed superior photocatalytic activity of GOM having a higher efficiency than TiO2. We propose a plausible mechanism for the formation of various morphologies of alpha-GaOOH and alpha-Ga2O3.