Nitrogen-Doped Porous Carbon-Supported Cu–Ni Single-Atom Catalysts for Green Ammonia Synthesis via Renewable-Powered Nitrogen Reduction Reaction

Ammonia (NH3) plays a pivotal role in industrial production and human life. The conventional method of ammonia production via the Haber–Bosch route, which operates under stringent conditions, incurs considerable energy expenditure and contributes to the release of greenhouse gases. Therefore, the development of advanced environmentally friendly methods for NH3 synthesis is of great importance. This research endeavors to produce environmentally friendly NH3 by harnessing the electrocatalytic nitrogen reduction reaction, powered by sustainable electricity sources, and investigate the efficacy of catalysts for this process. Non-noble-metal NiCu double single-atom-loaded nitrogen-doped porous carbon (NC@NiCu) was obtained by electrochemical deposition. Experimental results show that NC@NiCu has abundant dual single-atom Ni–Cu active sites, demonstrating excellent electrocatalytic N2 reduction performance, with a Faradaic efficiency of 30.0% and an ammonia yield rate of 70.78 μg·h–1·mgcat.–1, superior to many reported single-atom materials. The confirmation of uniformly dispersed Ni–Cu dual single-atom sites was achieved through the application of high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure analysis. Moreover, the product of the electrochemical NRR was identified as NH3, which was detected using differential electrochemical mass spectrometry, and density functional theory calculations revealed that the energy barrier for the transformation from *N2H to *NHNH on NC@NiCu is 0.72 eV, which is 0.69 eV higher than the energy barrier from *N2H to *NNH2 (0.03 eV). This significant difference in energy barriers indicates that the NRR on NC@NiCu proceeds via a distal mechanism. This research introduces an innovative method for the fabrication of nitrogen fixation materials with high catalytic activity and simultaneously establishes a fresh foundation for the development of future materials featuring dual single-atom configurations. Such advancements are pivotal for the realization of environmentally friendly and sustainable ammonia production techniques.