Regulating Interfacial Water Structure on CoNi/MoN Heterostructures Boosts Electrocatalytic Nitrate Reduction to Ammonia

ABSTRACT The electrochemical nitrate reduction reaction (NO 3 − RR) offers an attractive route for removing NO 3 − pollution and sustainably producing ammonia (NH 3 ). Rational regulation of *H species supply and key intermediates adsorption is critical for enhancing NO 3 − RR performance. Herein, we design a heterostructured CoNi/MoN catalyst, where MoN nanosheets are decorated with CoNi nanoparticles, to optimize the interfacial water structure and intermediates adsorption. This heterostructured catalyst exhibits a high NH 3 Faradaic efficiency of 96.8% and an attractive NH 3 yield rate of 22.3 mg h −1 cm −2 , outperforming most of the reported electrocatalysts under same NO 3 − concentration. Furthermore, using CoNi/MoN/NF as both the anode and cathode, a two‐electrode system coupling NO 3 − RR with 5‐hydroxymethylfurfural oxidation reaction achieves highly effective co‐production of NH 3 and 2,5‐furandicarboxylic acid. Experimental and theoretical calculation results reveal that the strong metal‐support interaction between CoNi nanoparticles and MoN nanosheets induces electron transfer from CoNi species to MoN nanosheets. The electron‐enriched MoN sites at the CoNi/MoN interface can efficiently capture K + to form K + ‐hydrated water (K + ‐H 2 O), which facilitates H 2 O dissociation to generate *H for accelerating the hydrogenation steps of NO 3 − RR. Meanwhile, the electron‐deficient CoNi nanoparticles with the upshifted d‐band center enhance NO 3 − adsorption and reduce the free energy barrier of NO 3 − RR.