A Symmetric Cogeneration Fuel Cell for Coupled Production of Hydrogen, Ammonia and Formate.

Electrochemical synthesis offers a sustainable route to convert abundant feedstocks into value-added chemicals under mild conditions and couple chemical manufacturing with renewable electricity. However, its practical impact is often limited by system-level energy inefficiency, motivating rational reaction pairing to reduce energy input while upgrading product value. Here, we develop a symmetric cogeneration fuel cell that couples one-electron formaldehyde oxidation reaction with nitrate reduction to co-produce hydrogen, ammonia and formate while generating electricity. This symmetric cell was enabled by a FOR and NO3RR bifunctional Cu nano leaves coated with Co(OH)2 catalyst, which constructs an interfacial hydrogen network capable of synchronizing NO3 - reduction with active hydrogen delivery. As a result, the catalyst achieves an industrial current density of 2.35 A cm-2 at -1 V vs RHE with a high Faradaic efficiency of 96.38%. Operating at 35°C, the symmetric cell delivers a peak power density of 13.24 mW cm-2, representing the highest value reported to date for unassisted ammonia synthesis systems. This work establishes a simple yet versatile strategy for integrating value-added chemical synthesis with electricity generation and offers a generalizable framework for other paired electrosynthesis processes.