Pulsed electroreduction of low-concentration nitrate to ammonia

Abstract Electrocatalytic nitrate (NO3−) reduction to ammonia (NRA) has emerged as an alternative strategy for effluent treatment and ammonia production. Although significant advances have been made in this area, the efficient conversion of low-concentration nitrate to emission standards (≤ 0.81 mM) is still a major challenge due to the scarce distribution of negatively charged NO3− in the vicinity of the working electrode. Here, we adopt the pulsed electrocatalysis technique to overcome this issue, and a remarkable NRA performance (Faradaic efficiency: 97.6%, yield rate: 2.72 mmol h−1 mgRu−1, conversion rate: 96.38%) is achieved for low-concentration (≤10 mM) nitrate reduction, obviously exceeding the potentiostatic test (Faradaic efficiency: 65.8%, yield rate: 1.05 mmol/h/mgRu, conversion rate: 54.08%). The combined results of in situ characterizations and finite element analysis unveil the performance enhancement mechanism that the periodic appearance of anodic potential can significantly optimize the adsorption configuration of the key *NO intermediate and increase the local NO3− concentration. More importantly, our work suggests a way toward rational design and manipulating catalysts and reaction processes that could find wider and greener catalytic applications.