Highly Durable and Selective Fe- and Mo-Based Atomically Dispersed Electrocatalysts for Nitrate Reduction to Ammonia via Distinct and Synergized NO₂^- Pathways

Aimed toward the pursuit of manufacturing ammonia in a carbon-neutral and decentralized manner, the electrocatalytic nitrate reduction reaction (NO₃RR) not only promises an effective route for carbon-neutral ammonia synthesis but also offers potential advantages to wastewater remediation. Here, we describe the efficacy of bioinspired, atomically dispersed catalysts for the NO₃RR in aqueous media via a catalytic cascade. Compared to nanoparticles with extended catalytic surfaces, atomically dispersed catalysts are largely underexplored in this field, despite their intrinsic selectivity toward mono-nitrogen species over their dinitrogen counterparts. Herein, we specifically report on a series of nitrogen-coordinated mono- and bimetallic, atomically dispersed, iron- and molybdenum-based electrocatalysts for ammonia synthesis via the NO₃RR. The key role of the *NO₂/NO₂^-intermediates was identified both computationally and experimentally, wherein the Fe-N₄sites and Mo-N₄/*O-Mo-N₄sites carried distinct associative and dissociative adsorption of NO₃^-molecules, respectively. By integrating individual Fe and Mo sites on a single bimetallic catalyst, the unique reaction pathways were synergized, achieving a Faradaic efficiency of 94% toward ammonia. Furthermore, the robustness of the bimetallic FeMo-N-C catalyst was highlighted by five consecutive 12 h electrolysis cycles with the Faradaic efficiency being maintained above 90% over the entire 60 h. The utilization of catalytic cascades, synergizing distinct reaction pathways on heterogeneous single-atom sites, is largely unconstrained by linear scaling relations of reaction intermediates and sheds light on designing electrocatalysts for highly selective, efficient, and durable ammonia synthesis.