Steering charge dynamics and surface reactivity for photocatalytic selective methane oxidation to ethane over Au/Ti-CeO2

Abstract

The selective oxidation of methane to value-added chemicals under mild conditions presents a sustainable yet challenging route, hindered by sluggish CH₄ activation and overoxidation. Herein, we report a delicate strategy combining Ti doping and Au loading to construct a high-performance Au/Ti-CeO₂ photocatalyst for ethane production from oxidative methane coupling. The optimized catalyst achieves a C₂H₆ production rate of 2971.4 μmol g⁻¹ h⁻¹ with 85.1 % C₂₊ selectivity, stably operating over 20 reaction cycles. In situ X-ray photoelectron spectroscopy, electron paramagnetic resonance, and diffuse reflectance infrared Fourier transform spectroscopy analyses reveal that Ti doping introduces impurity energy levels into CeO₂, promoting directional electron migration to surface Au nanoparticles (NPs) via a built-in electric field. The Au NPs act as electron accumulation sites to activate O₂, facilitate ∗CH₃ radical coupling into C₂H₆, and stabilize reactive intermediates, thus enhancing charge separation and suppressing intermediate overoxidation. This study highlights the significance of synergistic modulation via elemental doping and cocatalyst engineering in tuning charge dynamics and surface reactivity for efficient photocatalytic methane conversion.