In Situ Exsolution to Form Cu Nanoparticles on Cu–Doped LaFeO ₃ Perovskite Oxides for Efficient Electrocatalytic Reduction of Nitrate to Ammonia

Abstract Perovskite oxides hold significant potentials for catalytic applications due to their unique electronic structure and favorable chemical properties, whereas their intrinsic catalytic activity toward the electrocatalytic nitrate reduction reaction (NITRR) for NH ₃ production remains very limited yet needs to be further improved. Herein, a dual–engineering approach is proposed, combining Cu–mediated cation substitution and in situ exsolution for the construction of Cu nanoparticles on Cu–doped LaFeO ₃ perovskites (LFC–E) to address these limitations. The optimal LF3C7–E exhibits the highest NITRR performance with an NH ₃ yield rate of 4.1 mg h ⁻¹ mg _cat ⁻¹ and Faradaic efficiency of 76% at −0.7 V, which is superior to the corresponding LFC–P without exsolution treatment. The in situ Fourier transform infrared spectroscopy in combination with density functional theory calculations reveals that the synergistic effect between LaFeO ₃ and Cu enables the efficiently decreased energy barrier for the hydrogenation step of *NO (*NO + H ⁺ + e ⁻ → *NOH + H ₂ O), which is considered as the rate–determining step during the NITRR process. Moreover, an aqueous Zn–NO ₃ ⁻ battery and Zn–NO ₂ ⁻ battery with the optimal LF3C7–E as the cathode is assembled and achieves simultaneously electricity supply and NH ₃ production.