Facile and Scalable Synthesis of Self-Supported Zn-Doped CuO Nanosheet Arrays for Efficient Nitrate Reduction to Ammonium

CuO has been regarded as a promising catalyst for the electrochemical reduction of nitrate (NO3–RR) to ammonium (NH3); however, the intrinsic activity is greatly restricted by its poor electrical property. In this work, self-supported Zn-doped CuO nanosheet arrays (Zn–CuO NAs) are synthesized for NO3–RR, where the Zn dopant regulates the electronic structure of CuO to significantly accelerate the interfacial charge transfer and inner electron transport kinetics. The Zn–CuO NAs are constructed by a one-step etching of commercial brass (Cu64Zn36 alloy) in 0.1 M NaOH solution, which experiences a corrosion–oxidation–reconstruction process. Initially, the brass undergoes a dealloying procedure to produce nanosized Cu, which is immediately oxidized to the Cu2O unit with a low valence state. Subsequently, Cu2O is further oxidized to the CuO unit and reconstructed into nanosheets with the coprecipitation of Zn2+. For NO3–RR, Zn–CuO NAs show a high NH3 production rate of 945.1 μg h–1 cm–2 and a Faradaic efficiency of up to 95.6% at −0.7 V in 0.1 M Na2SO4 electrolyte with 0.01 M NaNO3, which outperforms the majority of the state-of-the-art catalysts. The present work offers a facile yet very efficient strategy for the scale-up synthesis of Zn–CuO NAs for high-performance NH3 production from NO3–RR.