Improved nitrate-to-ammonia electrocatalysis through hydrogen poisoning effects

Abstract Electrochemical nitrate-to-ammonia conversion affords an efficient approach for carbon-free ammonia production and nitrate pollutant removal. However, it suffers from low productive efficiency or high energy consumption due to lack of desired electrocatalysts. Here we report cobalt-doped nickel phosphides supported on carbon cloth for nitrate-to-ammonia electrocatalysis that display a record-high ammonia production rate of 88.4 g g cat −1 h − 1 and Faraday efficiency of ~ 100% at low energy consumption of 22.7 kWh kg ammonia −1 . In situ experiments and theoretical calculations reveal that these catalysts benefit from hydrogen poisoning effects on catalyst surface under low overpotentials, which leave behind the catalytically inert poisoned hydrogen atoms and in turn enable ideally reactive ones around them. The former blocks their nearby hydrogen-hydrogen dimerization for hydrogen evolution while the latter drives nitrate hydrogenation timely. With these catalysts, a profitable technology for continuous ammonia production and formaldehyde capture is further shown in an improved flow cell.