Single atomic cerium sites anchored on nitrogen-doped hollow carbon spheres for highly selective electroreduction of nitric oxide to ammonia

Abstract

Electrocatalytic nitric oxide reduction reaction (NORR) at ambient environments not only offers a promising strategy to yield ammonia (NH3) but also degrades the NO contaminant; however, its application depends on searching for high-performance catalysts. Herein, we present single atomic Ce sites anchored on nitrogen-doped hollow carbon spheres that are capable of electro-catalyzing NO reduction to NH3 in an acidic solution, achieving a maximal Faradaic efficiency of 91 % and a yield rate of 1023 μg h−1 mgcat.−1 at –0.7 V vs RHE for NH3 formation, both of which outperform these on Ce nanoclusters and approach the best-reported results. Meanwhile, the single atomic Ce catalyst shows good structural and electrochemical stability during the 30-h NO electrolysis. Furthermore, when the single atomic Ce catalyst was used as cathodic material in a proof-of-concept of Zn–NO battery, it delivers a maximal power density of 3.4 mW cm−2 and a high NH3 yield rate of 309 μg h−1 mgcat.−1. Theoretical simulations suggest that the Ce-N4 active moiety can not only activate NO molecules via a strong electronic interaction but also reduce the free energy barrier of *NO transition to *NOH intermediate as the limiting step, and therefore boosting the NORR kinetics and suppressing the competitive hydrogen evolution.