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 mu g 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.