Cu-Ru Bicenter Synergistically Triggers Tandem Catalytic Effect for Electroreduction of Nitrate to Ammonium

The electrochemical transformation of nitrate (NO₃⁻) into ammonia (NH₃) holds significant promise to addresses nitration contamination and offers a sustainable alternative to the Haber–Bosch process. However, the sluggish kinetics hinders its large-scale application. Herein, a Cu-doped SrRuO₃ synergetic tandem catalyst is designed and synthesized, which demonstrates exceptional performance in converting NO₃⁻ to NH₃. Specifically, this catalyst achieves a maximum Faradaic efficiency of 95.4% for ammonia production, along with a high yield rate of 7196 µg h⁻¹ mg_cat.⁻¹. A series of detailed characterizations reveals that the doped Cu ions modify the local electronic environment of Ru 4d e_g orbital in SrRuO₃, thereby facilitating highly efficient electron transfer processes. In situ delta X-ray absorption near-edge structure (ΔXANES), synchrotron radiation-based Fourier transform infrared (SR-FTIR) and Raman spectroscopy identified the ^*NO₂⁻ generated on the Cu active sites is subsequently hydrogenated on the Ru sites. Combined with theoretical studies, it is confirmed that the tandem catalyst significantly reduces the energy barriers of the rate-determining step (^*NO to ^*NOH), thereby enhancing the efficiency of ammonia synthesis. This work not only offers fundamental insights into the mechanisms of cation substitution on regulating the e_g orbital of perovskite catalysts, but also provides a promising avenue for the electro-synthesis of ammonia.