Copper–Nickel Oxide Nanosheets with Atomic Thickness for High‐Efficiency Sulfur Ion Electrooxidation Assisted Nitrate Electroreduction to Ammonia

Abstract

The nitrate electroreduction reaction (NO3RR) offers an eco‐friendly alternative to the Haber–Bosch technology for ammonia (NH3) synthesis. However, the complex reaction process and diverse products make efficient NH3 synthesis challenging. Therefore, the rational design and preparation of highly efficient electrocatalysts are crucial for NO3RR. Herein, ultrathin copper‐nickel oxide (Cu‐NiO) nanosheets (Cu‐NiO UTNSs) are synthesized via the cyanogel‐NaBH4 hydrolysis‐reduction method, which are applied for the cathodic NO3 RR to NH3‐assisted with the anodic sulfur ion (S2−) oxidation reaction (SOR) in an electrolyzer. The ultrathin nanosheet structure, the interaction between NiO and Cu, and the formation of oxygen vacancy contribute to generating the rich active sites, regulating the electronic structure, and improving the substance adsorption. Thus, the Cu‐NiO UTNSs exhibit excellent electrocatalytic performance for NO3RR and SOR. As a bifunctional Cu‐NiO UTNSs||Cu‐NiO UTNSs electrolyzer, it can reach 10 mA cm−1 at only 0.1 V for NO3−‐to‐NH3 conversion at the cathode and S2−‐to‐S8 conversion at the anode. This work provides a promising approach for producing value‐added chemicals at a low electrolysis voltage and a strategy for pollutant treatment.