Electrochemical Spillover Oxygen Species on Au Surface for Methane Oxidative Coupling

Selective oxidative coupling of methane is fundamentally constrained by the lack of controllable oxygen species for C-H bond activation. Here, we show that electrochemical spillover oxygen species on the Au anode surface in solid oxide electrolysis cells could effectively dictate the CH₄ activation pathways. In situ spectroscopy combined with theoretical analysis reveals that anodic polarization produces two oxygen species with distinct reactivity. Under anodic polarization, CH₄ activation proceeds predominantly via a methyl radical-mediated pathway, as directly evidenced by synchrotronic photoionization mass spectrometry, thereby enabling selective gaseous C-C coupling. This study deepens the understanding of the nature of electrochemical spillover oxygen while establishing a mechanistic framework for electrochemical modulation of oxygen states to steer selective CH₄ oxidation.