CuSiO 3 Strengthens *NO 2 Intermediate Affinity toward Highly Selective Electrocatalytic Nitrate Reduction to Ammonia

Developing high-performance catalysts for the electrochemical nitrate reduction reaction (NO 3 – RR) is crucial for sustainable ammonia (NH 3 ) production. Herein, we report copper silicate (CuSiO 3 ) as a highly efficient and selective catalyst for NH 3 production via the NO 3 – RR. In CuSiO 3, the alternately arranged Cu–O octahedra among stable Si–O tetrahedra prevent the active Cu 2+ 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 *NO 3 and *NO 2 . As a result, CuSiO 3 enhances the adsorption of the NO 3 – reactant to improve the NO 3 – RR activity and strengthens the affinity for *NO 2 to inhibit byproduct production. Consequently, CuSiO 3 delivers a high NH 3 yield of 214.5 μmol h –1 mg –1 and a selectivity of 97.1% in 0.1 M Na 2 SO 4 containing 10 mM NaNO 3, even when the applied potential is as negative as −1.1 V. This work not only demonstrates CuSiO 3 as a promising NO 3 – RR catalyst for the sustainable production of green NH 3 but also offers valuable insights into the rational design of copper-based catalysts for a wide range of applications.