Efficient and stable CH₄ conversion in a solid oxide steam electrolyzer is proposed to produce C₂₊ hydrocarbons and hydrogen synchronously, and the electro-spillover oxygen modulated surface C─H cleavage followed by the gaseous ·CH₃ radical coupling mechanism is elucidated.

Abstract

Catalytic methane (CH₄) upgrading to C₂₊ products has attracted widespread interest. However, non-oxidative coupling and oxidative coupling of CH₄ are limited by coking and over-oxidation, respectively. In this work, we propose an efficient and stable CH₄ conversion system in a solid oxide steam electrolyzer, enabling the simultaneous production of C₂₊ hydrocarbons and H₂. Furthermore, through various in situ characterizations, we reveal a gaseous ·CH₃ radical coupling mechanism underlying the electrochemical CH₄ conversion. These findings pave the way for the efficient design of the electrode for anodic CH₄ coupling reactions in a solid oxide electrolyzer and establish a new framework for atom-efficient strategies for CH₄ upgrading.