Thermo–Electrochemical Coupled Proton Relay Unlocks Efficient Nitrate‐to‐Ammonia Conversion on Metal‐Free Catalysts in Neutral Electrolytes

Electrochemical nitrate reduction to ammonia (NitRR) represents a promising strategy for sustainable ammonia production. However, efficient operation in neutral electrolytes remains challenging because proton‐coupled electron transfer is kinetically limited by the slow water‐dissociation‐mediated proton transfer process. Here we report a thermally activated interfacial proton‐transfer mechanism that enables efficient neutral NitRR on a metal‐free sulfonated carbon nitride catalyst (NC─SO 3 ). DFT calculations reveal that electrochemical protonation of surface sulfonate groups transiently generates ─SO 3 H intermediates, which act as local proton donors during electrocatalysis. Subsequent thermally enhanced proton transfer from these transient ─SO 3 H intermediates to nitrate intermediates adsorbed on neighboring graphitic nitrogen sites accelerates the hydrogenation steps without altering the adsorption centers of the NitRR pathway. This thermally‐electrochemically coupled process becomes increasingly effective at elevated temperatures. At 80°C, the catalyst exhibits activity surpassing state‐of‐the‐art nitrate reduction systems reported for both neutral and alkaline electrolytes. The mechanism is validated by the loss of thermal enhancement in alkaline electrolytes, where transient ─SO 3 H intermediates cannot be regenerated because the surface remains predominantly in the deprotonated ─SO 3 state. These results demonstrate that thermo‐electrochemically coupled proton relays provide an effective strategy to overcome proton‐transfer limitations in neutral electrolyts and enable efficient nitrate‐to‐ammonia conversion under practically relevant conditions.