Convergent Valorization via Scalable C=N Bond Electrosynthesis through Metal-Dopant Interfacial Engineering in a Flow Electrolyzer

Electrovalorization of C- and N-containing pollutants into carbonaceous and nitrogenous feedstocks is key to addressing environmental issues and realizing a sustainable society. Compared to C- or N-only reduction reactions, convergent electrocatalytic processes to form value-added C–N bond containing compounds have attracted increasing attention. Specifically, the exploration centers on the generation of oximes featuring C=N bonds, which are essential chemicals with widespread applications in the pharmaceutical and final chemical fields. Previous state-of-the-art work reported that formaldoxime, H2C=NOH, is electrosynthesized as a side product with a Faradaic efficiency of less than 6%. Here, we develop an integrated electrocatalytic platform to produce formaldoxime as the target product in a green solvent using metal-doped MoS2 as efficient catalysts. Notably, Fe-doped MoS2 significantly boosts the Faradaic efficiency and yield rate for H2C=NOH to a record-high 81% and 963 mmol⸳h–1⸳g–1, respectively. Kinetic isotopic effect studies and density functional theory computational analysis are carried out to unveil the electrocatalytic mechanism of this tandem C=N bond formation process and the importance of Fe dopants toward boosting the efficiency for C=N electrosynthesis. Upon incorporating into a flow electrolyzer, the yield rate for H2C=NOH electrosynthesis is drastically enhanced to 2630 mmol⸳h–1⸳g–1, almost tripled that obtained from H-cell setups. By tailoring the microenvironment of MoS2 nanosheets with Fe dopants, Fe-MoS2 exhibits an optimal binding affinity for NO2– than MoS2, thus enhancing substrate engagement and subsequently H2C=NOH formation in an aqueous medium. Overall, this work establishes a coherent strategy that upcycles low-cost C- and N-containing pollutants into valuable organonitrogens. This dual-upgrading process powered by renewable energy holds the potential to generate more structurally complicated and functionally diverse commodities.