Computational insights on potential dependence of electrocatalytic synthesis of ammonia from nitrate

Electrochemical nitrate reduction reaction (eNO3RR) has been considered as an alternative route for decentralized ammonia (NH3) synthesis. However, a major challenge is products selectivity at low overpotentials, namely, the competition between nitrite (HNO2) and ammonia. Herein, we employed single-atom catalyst (FeN4) model to study competitive mechanism of NH3 HNO2 by density functional theory calculations. It was found optimal paths productions share key intermediate (NO2*), whose adsorption structures preference in following conversion determines selectivity. We have incorporated potential-dependent barriers microkinetic modeling understand Faradaic efficiency different potentials. Our results are good agreement with experimental trend efficiencies HNO2, which can be rationalized well charge transfer coefficient (β) NO2* protonation cisHNO2* respect that HNO2. A production small overpotentials ascribed kinetic issue. The electron localization function crystal orbital Hamilton population were analyzed on initial transition states computational mechanistic insights help design new eNO3RR highly active selective NH3.