Constructing Ru@C3N4/Cu Tandem Electrocatalyst with Dual‐Active Sites for Enhanced Nitrate Electroreduction to Ammonia

Abstract Electroreduction of nitrate to ammonia reaction (NO3−RR) is considered as a promising carbon‐free energy technique, which can eliminate nitrate from waste‐water also produce value‐added ammonia. However, it remains a challenge for achieving satisfied ammonia selectivity and Faraday efficiency (FE) due to the complex multiple‐electron reduction process. Herein, a novel Tandem electrocatalyst that Ru dispersed on the porous graphitized C3N4 (g‐C3N4) encapsulated with self‐supported Cu nanowires (denoted as Ru@C3N4/Cu) for NO3−RR is presented. As expected, a high ammonia yield of 0.249 mmol h−1 cm−2 at −0.9 V and high FENH3 of 91.3% at −0.8 V versus RHE can be obtained, while achieving excellent nitrate conversion (96.1%) and ammonia selectivity (91.4%) in neutral solution. In addition, density functional theory (DFT) calculations further demonstrate that the superior NO3−RR performance is mainly resulted from the synergistic effect between the Ru and Cu dual‐active sites, which can significantly enhance the adsorption of NO3− and facilitate hydrogenation, as well as suppress the hydrogen evolution reaction, thus lead to highly improved NO3−RR performances. This novel design strategy would pave a feasible avenue for the development of advanced NO3−RR electrocatalysts.