Photocatalytic activities and photophysical properties of Ga2−xInxO3 solid solution

Photocatalytic activities of Ga2−xInxO3 solid solutions consisting of β-Ga2O3 with a wide band gap and In2O3 with a medium band gap were studied in order to develop new photocatalysts based on oxide solid solutions. The Ga2−xInxO3 solid solutions were characterized by X-ray diffraction, surface area, diffuse reflection spectra, photoluminescent and photoelectrochemical measurements. As the ratio of In was increased from x = 0 to 1 in Ga2−xInxO3, the lattice parameters were increased, indicating the formation of solid solutions as has previously been reported. Corresponding to this, the absorption, excitation and emission spectra were red-shifted, showing a decrease in the band gaps, and the flat band potentials were shifted positively. Among the solid solutions, GaInO3 (or Ga1.14In0.86O3) showed the highest photocatalytic activity for H2 evolution from aqueous methanol solutions and for O2 evolution from aqueous silver nitrate solutions. The dependency of the photocatalytic activities on the composition of the solid solutions was explained by taking the number of available photons and the flat band potentials into consideration.