Improved Nitrate‐to‐Ammonia Electrocatalysis through Hydrogen Poisoning Effects

Electrochemical conversion from nitrate to ammonia is a key step in sustainable ammonia production. However, it suffers from low productive efficiency or high energy consumption due to a lack of desired electrocatalysts. Here we report nickel cobalt phosphide (NiCoP) catalysts for nitrate‐to‐ammonia electrocatalysis that display a record‐high catalytic current density of −702±7 mA cm−2, ammonia production rate of 5415±26 mmol gcat−1 h−1 and Faraday efficiency of 99.7±0.2 % at −0.3 V vs. RHE, affording the estimated energy consumption as low as 22.7 kWh kgammonia−1. Theoretical and experimental results reveal that these catalysts benefit from hydrogen poisoning effects, which leave behind catalytically inert adsorbed hydrogen species (HI*) at Co‐hollow sites and thereupon enable ideally reactive HII* at secondary Co−P sites. The dimerization between HI* and HII* for H2 evolution is blocked due to the catalytic inertia of HI* thereby the HII* drives nitrate hydrogenation timely. With these catalysts, the continuous ammonia production is further shown in an electrolyser with a real energy consumption of 18.9 kWh kgammonia−1. Hydrogen poisoning effects over NiCoP@CC occurring at low overpotentials can leave behind catalytically inert poisoned HI* at Co‐hollow sites and thereby create ideally reactive HII*. The dimerization between HI* and HII* for HER was suppressed due to catalytic inertia of HI* and thereby NITRR was timely initiated through HII* owing to ideal hydrogenation reactivity of HII*. As a result, a record high NH3 production rate and Faraday efficiency were achieved at low energy consumption.