Tandem Catalysis in CuO/ZnMnO3 Heterostructures for Efficient Electrooxidation of N2 to Nitrate.

Nitrate is indispensable in modern agriculture and industry, yet its production via the energy-intensive Haber-Bosch and Ostwald oxidation processes results in significant carbon emissions. Electrocatalytic nitrogen oxidation reaction (eNOR) offers a highly sustainable and decentralized alternative for nitrate synthesis. However, the inherent challenge of N2 activation, stemming from its extremely inert triple bond, and the kinetically sluggish nature of the multielectron-transfer pathway severely impede its practical application. Inspired by multielectron cascade processes, we rationally engineered a CuO/ZnMnO3 heterostructure catalyst to leverage tandem catalysis, deconstructing the formidable multielectron-transfer pathway of N2 oxidation. This innovative heterostructure spatially decouples nitrogen activation from subsequent oxidation, effectively breaking down the overall reaction into lower-energy, stepwise transformations. The catalyst achieves an enhanced nitrate yield rate of 52.1 μmol h-1 mg-1 and a Faradaic efficiency of 45.2%, surpassing single-component benchmarks (1.6-fold higher activity than ZnMnO3) and most reported state-of-the-art eNOR catalysts with exceptional long-term stability. Through comprehensive kinetic analysis, in situ differential electrochemical mass spectrometry, and density functional theory calculations, we provide compelling evidence supporting the tandem reaction mechanism. Specifically, N2 is initially activated and partially oxidized to the key intermediate N2O on the ZnMnO3 component, which is then efficiently captured and further oxidized to nitrate on the CuO component. This work not only presents a highly efficient and stable catalyst for sustainable nitrate electrosynthesis but also validates tandem-site engineering as a strategic paradigm for managing complex multielectron transfer reactions.