Enzyme-inspired microenvironment engineering of atomic copper sites accelerates electrocatalytic nitrate-to-ammonia conversion

The electrocatalytic NO 3 - reduction reaction (NO 3 - RR) proves the feasibility for the synthesis of NH 3 under mild conditions, yet it still faces challenges such as poor product selectivity and low reaction rates. Inspired by biological enzymes that exhibit both high selectivity and superior reaction rates, we designed an enzyme-mimetic catalyst for highly efficient NO 3 - RR. Specifically, mesoporous carbon nanofibers (CNFs) act as confined microenvironments for the enrichment of reactants, and the synergistic catalysis of Cu nanoclusters (Cu NCs) and Cu single atoms (Cu SAs) can match the complex reaction pathways of multiple intermediates and multiple proton/electron transfers. Consequently, the as-synthesized Cu NCs&SAs @CNFs catalyst achieves a remarkable NH 3 Faradaic efficiency (FE) of 97.23 % and a high yield rate of 31.45 mg h −1 cm −1 . Additionally, we employed the Cu NCs&SAs @CNFs as a cathode to assemble a Zn-NO 3 - battery, the system maintains a stable open circuit voltage of 1.36 V over 10 h continuous operation. This work combines the regulation of active sites and tuning of microenvironments, which might provide some insights for designing enzyme-mimicking catalysts in various electrocatalytic systems.