Batch-Scale Synthesis of Nanoparticle-Agminated Three-Dimensional Porous Cu@CuO Microspheres for Highly Selective Electrocatalysis of Nitrate to Ammonia.

The electrochemical nitrate reduction reaction (NITRR), which converts nitrate to ammonia, is promising for artificial ammonia synthesis at mild conditions. However, the lack of favorable electrocatalysts has hampered its large-scale applications. Herein, we report the batch-scale synthesis of three-dimensional (3D) porous Cu@CuO microspheres (Cu@CuO MSs) composed of fine Cu@CuO nanoparticles (NPs) using a convenient electric explosion method with outstanding activity and stability for the electrochemical reduction of nitrate to ammonia. Density functional theory (DFT) calculations revealed that the CuO (111) facets could facilitate the formation of *NOH and *NOH intermediates and suppress the hydrogen evolution reaction (HER), resulting in high selectivity for the NITRR. Moreover, the 3D porous structure of Cu@CuO MSs facilitates electrolyte penetration and increases the localized concentration of reactive species for the NITRR. As expected, the obtained Cu@CuO MSs exhibited an ultrahigh NH production rate of 327.6 mmol·h·g (which is superior to that of the Haber-Bosch process with a typical NH yield <200 mmol hg), a maximum Faradaic efficiency of 80.57%, and remarkable stability for the NITRR under ambient conditions. Quantitative N isotope labeling experiments indicated that the synthesized ammonia originated from the electrochemical reduction of nitrate. Achieving the batch-scale and low-cost production of high-performance Cu@CuO MSs electrocatalysts using the electric explosion method is promising for the large-scale realization of selective electrochemical reduction of nitrate toward artificial ammonia synthesis.