Electrocatalytic Methane Oxidation Greatly Promoted by Chlorine Intermediates

Renewable energy-powered methane (CH₄ ) conversion at ambient conditions is an attractive but highly challenging field. Due to the highly inert character of CH₄ , the selective cleavage of its first C-H bond without over-oxidation is essential for transforming CH₄ into value-added products. In this work, we developed an efficient and selective CH₄ 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 CH₄ to CH₃ Cl without over-oxidation to CO₂ , and Ni³⁺ at the octahedral sites in the mixed cobalt-nickel spinels allowed to stabilize surface-bound *Cl species. The CoNi₂ O_x electrocatalyst exhibited an outstanding yield of CH₃ Cl (364 mmol g^-1 h^-1 ) and a high CH₃ Cl/CO₂ selectivity of over 400 at room temperature, with demonstrated capability of direct CH₄ conversion under seawater working conditions.