Electrochemical Reduction of Nitrates on CoO Nanoclusters‐Functionalized Graphene with Highest Mass Activity and Nearly 100% Selectivity to Ammonia

Abstract NO 3 − is a prominent waste byproduct in ammunition industries, and valorization of NO 3 − into NH 3 is desired. NH 3 synthesized from waste using renewable energy could be used as an energy storage medium. For such a process, higher selectivity, stability, and enhanced activity per unit mass of catalyst is required. This work reports CoO nanoclusters functionalized on graphene as an efficient catalyst for electrochemical NO 3 − reduction to NH 3 with >98% NH 3 Faradaic efficiency and an NH 3 current density (geometric) of ≈400 mA cm −2 . A highest NH 3 yield of 25.63 mol g −1 h −1 is obtained. The developed catalyst prevents the NN coupling step which is required for promoting the selectivity of NH 3 over N 2 . Density functional theory calculations reveal that CoO NC/graphene has similar selectivity to that of polycrystalline Co and that higher activity can be obtained with lower catalyst loading.