Improved Nitrate‐to‐Ammonia Electrocatalysis through Hydrogen Poisoning Effects

Abstract 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 g cat −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 kg ammonia −1 . Theoretical and experimental results reveal that these catalysts benefit from hydrogen poisoning effects, which leave behind catalytically inert adsorbed hydrogen species (H I *) at Co‐hollow sites and thereupon enable ideally reactive H II * at secondary Co−P sites. The dimerization between H I * and H II * for H 2 evolution is blocked due to the catalytic inertia of H I * thereby the H II * 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 kg ammonia −1 .