Evaluation of catalytic activity of Ga2O3–Al2O3 solid solutions for CH4-SCR by UV–vis spectra after adsorption of C3H6 as a probe

When γ-Ga2O3–Al2O3 solid solutions were treated with C3H6 followed by heating at 300 °C, they were colored yellow giving two bands at 340 nm (α band) and 430 nm (β band) in their UV–vis spectra. The α and β bands were closely related with surface tetrahedral (image)-Ga3+ and octahedral (image)-Ga3+ sites, respectively. The intensities of the two bands changed by γ-Ga2O3–Al2O3 solid solutions prepared by various methods, although they had almost the same proportions of image-Ga3+ sites in the bulk structure. The intensities of the two bands can be used to diagnose the catalytic activity of γ-Ga2O3–Al2O3 catalysts for CH4-SCR of NO.