Gallium Oxynitride Photocatalysts Synthesized from Ga(OH)3 for Water Splitting under Visible Light Irradiation

We report the synthesis of wurtzite-like gallium oxynitride (GaON) photocatalysts by nitridation of Ga(OH)(3) with NH3 at temperatures between 550 and 900 degrees C. Ga(OH)(3) is a more suitable precursor for GaON synthesis than Ga2O3, because its crystal lattice contains unoccupied 12-coordinate sites that facilitate ionic transportation during nitridation. The prepared GaON catalysts had band gap energies from 2.2 to 2.8 eV and showed significant activities in the visible-light promoted evolution of H-2 and O-2 gases from methanol and AgNO3 solutions, respectively. The maximum H-2 and O-2 evolution rates occurred for catalysts synthesized at 625 and 700 degrees C, respectively. These active catalysts had an N/O atomic ratio close to unity, suggesting that extensive hybridization of N-2p and O-2p orbitals promotes charge mobility, and thus enhances photocatalytic activity. This study highlights the interesting possibility of synthesizing a large diversity of visible-light active, III-oxynitride catalysts using this Ga(OH)(3) route.