Electron-deficient Mo sites enhance electrochemical nitrate reduction to ammonia by promoting water dissociation

Abstract

The electrochemical nitrate reduction reaction (NITRR) offers a sustainable approach for converting nitrate contaminants into valuable ammonia. However, the performance of the NITRR is hindered by sluggish hydrogenation steps involving active hydrogen (*H). Herein, nanoporous Mo-doped Co₂P (np-Mo-Co₂P) is reported as an excellent electrocatalyst for the NITRR. In situ spectroscopy and theoretical calculations reveal that the introduction of electron-deficient Mo sites enhances H₂O adsorption and reduces the energy barrier for H₂O dissociation, thereby providing sufficient *H for the NITRR hydrogenation steps. Meanwhile, the np-Mo-Co₂P catalyst exhibits a strong interaction with the *NO intermediate, lowering the energy barrier for *NO hydrogenation and facilitating the NITRR process. As a result, the np-Mo-Co₂P catalyst achieves nearly 100% faradaic efficiency for NH₃ and an energy efficiency of 40.6% at −0.1 V vs. RHE, outperforming most of the recently reported NITRR catalysts. Furthermore, the np-Mo-Co₂P-based Zn-NO₃⁻ battery exhibits a high power density of 21.30 mW cm⁻². This work indicates the promising electrocatalytic application of electron-deficient active sites towards the NITRR and provides an intriguing strategy to enhance the reduction of inert intermediates by optimizing the *H supply.