Efficient photocatalytic oxidation of methane over β-Ga2O3/activated carbon composites

Efficient oxidation of methane over heterogeneous catalysts under ambient conditions is still a challengeable study toward C1 utilization and atmospheric cleansing. In this study, by using a hydrolysis method combined with an impregnation process, beta-Ga2O3 nanoparticles supported uniformly on activated carbon (AC) can be obtained readily. The as-prepared Ga2O3/AC composites show efficient performance for photocatalytic oxidation of CH4 under ultraviolet irradiation. The experimental results indicate that photocatalytic activity toward CH4 oxidation is strongly dependent on the weight ratio of Ga2O3 to AC. 15%-Ga2O3/AC exhibits the highest catalytic activity, which is more than sixfold of P25, a benchmark photocatalyst. The photoluminescence spectra show the decreased recombination centers and the diminished recombination of photo-generated electrons (e(-)) and holes (h(+)) when Ga2O3 nanoparticles were deposited on AC. Further investigation reveals that the excellent photo-oxidation activity for CH4 over Ga2O3/AC can be ascribed to a synergistic effect involving strong adsorption capacity and improved separation of photo-generated e(-)/h(+) pairs. Moreover, the photocatalytic oxidation of CH4 obeys pseudo-first-order kinetics and the cycling experiment indicates that Ga2O3/AC composites possess stable photocatalytic performance for CH4 oxidation. The underlying photo-oxidation mechanism is also investigated using electron paramagnetic resonance (ESR) and radical scavenging experiments. This study demonstrates that photocatalysis with Ga2O3/AC is a highly efficient method toward the oxidation of low concentrations of CH4, which provides valuable information for atmospheric environmental cleansing.