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

Abstract

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, β-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.