CuSiO3 Strengthens *NO2 Intermediate Affinity toward Highly Selective Electrocatalytic Nitrate Reduction to Ammonia

Developing high-performance catalysts for the electrochemical nitrate reduction reaction (NO3–RR) is crucial for sustainable ammonia (NH3) production. Herein, we report copper silicate (CuSiO3) as a highly efficient and selective catalyst for NH3 production via the NO3–RR. In CuSiO3, the alternately arranged Cu–O octahedra among stable Si–O tetrahedra prevent the active Cu2+ centers from being transformed to the metallic Cu phase, thereby effectively suppressing the competing hydrogen evolution reaction. Meanwhile, Si–O bonds withdraw electrons from Cu sites, leading the remaining electrons fill low-energy orbitals for a lower d-band center. This electron-withdrawing effect generates more vacant or partially filled Cu d orbitals that can accept electrons from the highest occupied molecular orbitals (HOMO) of adsorbed *NO3 and *NO2. As a result, CuSiO3 enhances the adsorption of the NO3– reactant to improve the NO3–RR activity and strengthens the affinity for *NO2 to inhibit byproduct production. Consequently, CuSiO3 delivers a high NH3 yield of 214.5 μmol h–1 mg–1 and a selectivity of 97.1% in 0.1 M Na2SO4 containing 10 mM NaNO3, even when the applied potential is as negative as −1.1 V. This work not only demonstrates CuSiO3 as a promising NO3–RR catalyst for the sustainable production of green NH3 but also offers valuable insights into the rational design of copper-based catalysts for a wide range of applications.