Precisely Constructing Ag ₁ /C ₃ N ₄ Dual‐Site for Highly Efficient Chlorine‐Mediated Electrocatalytic Methane Valorization

Electrocatalytic conversion of CH 4 to CH 3 Cl offers a sustainable route for inert alkane valorization. The core challenge is the tension between activating the initial C─H bond and suppressing sequential dehydrogenation, which critically depends on the electrogenerated *Cl mediators. Here, we construct a silver single‐atom electrocatalyst on graphitic carbon nitride (Ag 1 /C 3 N 4 ) that enables *Cl generation at the C site of the C 3 N 4 support, markedly facilitating the *Cl generation and selective methane chlorination. In a flow cell with saturated NaCl at ambient conditions, Ag 1 /C 3 N 4 attains a benchmark CH 3 Cl yield of 1784.5 mmol g −1 h −1 with 88.0% selectivity at 1.8 V vs. Ag/AgCl. Combined experimental and computational insights reveal that the electrogenerated *Cl locally restructures the Ag 1 –C 3 N 4 interface to contribute to a synergistic Ag─N─C─*Cl site that promotes CH 4 activation and chlorination. This *Cl‐induced metal‐support synergy markedly lowers the energy demand for initial C─H cleavage (from 1.32 to 0.67 eV) and CH 3 Cl formation (from 1.52 to 0.83 eV), with a low CH 3 Cl desorption energy (0.27 eV) to suppress over‐dehydrogenation. This work establishes a *Cl‐mediated dual‐site pathway for electrocatalytic methane valorization, offering a promising strategy for mediator‐guided active site engineering in challenging inert‐alkane valorization.