A direct complete dissociation mechanism for nitrate reaction to ammonia

Abstract

Nitrate electroreduction (NO3ER) is essential to improve water quality and nitrogen cycle in nature. However, developing efficient catalysts remains a challenge due to the unclear reaction mechanism. Herein, taking transition metal dual-atom supported on hexa-nitrogen coordinated graphene as an example to explore its potential mechanism as the NO3ER electrocatalysts by using density functional theory (DFT) computations. The results revealed the NO3ER prefers to take place via a complete-dissociation pathway, in which the adsorbed *NO3 species was dissociated into (*O + *NO2), which eventually generated the NH3 product by alternating hydrogenation and dissociation. Remarkably, based on a two-step screening strategy, CrFe on hexa-nitrogen coordinated graphene was extracted from various dual atom catalysts with an ultra-low limiting potential (−0.12 V). In addition, the selectivity of CrFe on hexa-nitrogen coordinated graphene can overcome competing reactions, and thus it can be identified as an ideal electrocatalyst for NO3ER. Our findings not only contribute to a deeper understanding of the NO3ER mechanism on dual-atom catalysts, but also provide theoretical guidance for the exploration of efficient NO3ER catalysts.