Aimed toward the pursuit of manufacturing ammonia in a carbon-neutral and decentralized manner, the electrocatalytic nitrate reduction reaction (NO 3 RR) 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 NO 3 RR 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 NO 3 RR. The key role of the *NO 2 /NO 2 − intermediates was identified both computationally and experimentally, wherein the Fe−N 4 sites and Mo−N 4 /*O− Mo−N 4 sites carried distinct associative and dissociative adsorption of NO 3 − 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.

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Electrocatalytic reduction of waste nitrates (NO3−) enables the synthesis of ammonia (NH3) in a carbon neutral and decentralized manner. Atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts demonstrate a high catalytic activity and uniquely favor mono-nitrogen products. However, the reaction fundamentals remain largely underexplored. Herein, we report a set of 14; 3d-, 4d-, 5d- and f-block M-N-C catalysts. The selectivity and activity of NO3− reduction to NH3 in neutral media, with a specific focus on deciphering the role of the NO2− intermediate in the reaction cascade, reveals strong correlations (R=0.9) between the NO2− reduction activity and NO3− reduction selectivity for NH3. Moreover, theoretical computations reveal the associative/dissociative adsorption pathways for NO2− evolution, over the normal M-N4 sites and their oxo-form (O-M-N4) for oxyphilic metals. This work provides a platform for designing multi-element NO3RR cascades with single-atom sites or their hybridization with extended catalytic surfaces.