Highly Acid-Resistant\nCo<sub>NPs</sub>@Co-N‑C\nCatalyst for the Efficient Aqueous-Phase Hydrogenation of Maleic Acid\nto Succinic Acid

Aqueous-phase\nhydrogenation holds significance in achieving\nthe\nlarge-scale green production of succinic acid, but the acidic reaction\nenvironment poses a considerable challenge in the design of highly\nactive and stable catalysts. Herein, we report a spatial-confinement\nstrategy to fabricate a Co<sub>NPs</sub>@Co-N-C core–shell\nstructured catalyst where Co nanoparticles (Co<sub>NPs</sub>) are\nencapsulated tightly by nitrogen-doped graphitic carbon shells (NG),\nwhile Co single atoms (Co<sub>SA</sub>) are distributed homogeneously\non the shells, which exhibits remarkable efficiency and stability\nin the aqueous-phase hydrogenation of maleic acid for the production\nof succinic acid in an acidic medium. The catalyst achieves 100% conversion\nof maleic acid, more than 98% selectivity toward succinic acid, and\nhigh stability for seven cycles without significant deactivation.\nThe combined characterizations and density functional theory (DFT)\ncalculations further indicate that Co<sub>NP</sub> and Co<sub>SA</sub> can concurrently optimize the electronic structure of the NG and\npromote hydrogen dissociation on the surface of the carbon shells.\nThese findings shed light on the unique function of Co<sub>NP</sub>-NG-Co<sub>SA</sub> composite sites on regulating the hydrogenation\nactive centers and provide a guideline for the further development\nof highly efficient acid-resistant hydrogenation catalysts.