Photocatalytic methane oxidation over a TiO2/SiNWs p-n junction catalyst at room temperature.

Rapid recombination of charge carriers in semiconductors is a main drawback for photocatalytic oxidative coupling of methane (OCM) reactions. Herein, we propose a novel catalyst by developing a p-n junction titania-silicon nanowires (TiO₂/SiNWs) heterostructure. The structure is fabricated by atomic layer deposition of TiO₂ on p-type SiNWs. The TiO₂/SiNWs heterostructure exhibited an outstanding OCM performance under simulated solar light irradiation compared to the single components. This enhanced efficiency was attributed to the intrinsic electrical field formed between n-type TiO₂ and p-type SiNWs, which forces generated charge carriers to move in opposite directions and suppresses charge recombination. Besides, surface morphology and optical properties of the the p-n TiO₂/SiNWs catalyst are also beneficial for the photocatalytic activity. It is expected that the results of this study will provide massive guidance in synthesizing an efficient photocatalyst for CH₄ conversion under mild conditions.