Ultrawide Potential Window for Ammonia Electrosynthesis on a Bifunctional Metal−Organic Framework Across Broad Nitrate Concentrations

Adaptability to the fluctuating supply of renewable electricity is one of the most critical challenges in realizing green ammonia electrosynthesis, especially when dealing with wastewater containing low concentration nitrate. Here, we report spatial electronic engineering of metal-organic frameworks (MOFs) that achieves an ultrawide potential window of 700 mV for nitrate reduction to ammonia (NRA) in 100 mM nitrate electrolyte and Faradaic efficiencies exceeding 90% over a broad nitrate concentration range (10-100 mM), superior to almost all reported catalysts. Coupling with the thermodynamically favorable glycerol oxidation reaction (GOR), simultaneous NRA||GOR reaches 50 mA·cm^-2 at 1.16 V, 230 mV below the conventional oxygen evolution reaction (OER) based NRA||OER. Furthermore, the paired system can continuously operate at an industrial current density (∼200 mA·cm^-2) over 100 h. The spatial electronic engineering lowers the d-band center and work function of the resulting bifunctional MOF and energy barrier of the rate determining step (RDS) while promoting water dissociation and suppressing hydrogen evolution. The ultrawide potential window and spontaneous nitrate adsorption equip the catalyst with excellent adaptability to renewable electricity and low-concentration nitrate water treatment, exhibiting dual sustainability advantage.