Selective Electrosynthesis of Ammonia via Sequential Electron–Proton Transfer

The proton-coupled electron transfer (PCET) process is central to sustainable electrochemical energy conversion (e.g., electrocatalytic nitrate reduction (NO 3 RR) to ammonia). Decoupling electron transfer (ET) and proton transfer (PT) could suppress the *H dimerization that happens in the Volmer–Tafel process, thereby enhancing activity and product selectivity. Herein, we demonstrate that π-conjugated cyanamide (NCN 2– ) groups featuring a flexible structure ([N═C═N] 2– ⇔ [N≡C─N] 2– ) function as an electron accelerator and proton relay in NO 3 RR, leading to a decoupled ETPT process. The electron-withdrawing [N═C═N] 2– induces the polarization of [Bi 2 O 2 ] catalytic layers, with more σ holes and an enhanced surface electrostatic potential ( V S ( r )), which facilitates ET and forms high-valence NO 3 (1+δ)– (δ > 1) traps. Simultaneously, switchable [N≡C─N] 2– serves as a proton relay that accelerates PT in the hydrogenation of NO x intermediates. This sequential ETPT is validated by various in situ experimental characterizations and molecular dynamic modeling. The ETPT-dominant NO 3 RR process achieves 95.3% Faradaic efficiency for NH 3 and stably works for over 500 h at an industrial current density (500 mA cm –2 ) in a paired electro-refinery system. This work establishes sequential ETPT regulation as a general strategy for optimizing PCET-mediated sustainable energy conversion systems.