Electrocatalytic Methane Oxidation Greatly Promoted by Chlorine Intermediates

Renewable energy‐powered methane (CH 4 ) conversion at ambient conditions is an attractive but highly challenging field. Due to the highly inert character of CH 4 , the selective cleavage of its first C−H bond without over‐oxidation is essential for transforming CH 4 into value‐added products. In this work, we developed an efficient and selective CH 4 conversion approach at room temperature using intermediate chlorine species (*Cl), which were electrochemically generated and stabilized on mixed cobalt–nickel spinels with different Co/Ni ratios. The lower overpotentials for *Cl formation enabled an effective activation and conversion of CH 4 to CH 3 Cl without over‐oxidation to CO 2 , and Ni 3+ at the octahedral sites in the mixed cobalt–nickel spinels allowed to stabilize surface‐bound *Cl species. The CoNi 2 O x electrocatalyst exhibited an outstanding yield of CH 3 Cl (364 mmol g −1  h −1 ) and a high CH 3 Cl/CO 2 selectivity of over 400 at room temperature, with demonstrated capability of direct CH 4 conversion under seawater working conditions.