Size-Dependent Copper Nanoparticles Supported on Carbon Nanotubes with Balanced Cu⁺ and Cu⁰ Dual Sites for the Selective Hydrogenation of Ethylene Carbonate

Cyclic carbonate hydrogenation offers an alternative for the efficient indirect CO₂ utilization. In this study, a series of carbon nanotubes (CNTs) supported xCu/CNTs catalysts with different Cu loadings were fabricated using a convenient impregnation method, and exhibited excellent catalytic activity for the hydrogenation of ethylene carbonate to methanol and ethylene glycol. The structural and physicochemical properties revealed that acid treatment of CNTs resulted in plentiful oxygen-containing functional groups, providing sufficient anchoring sites for copper species. The calcination process conducted under an inert atmosphere resulted in the formation of ternary CuO, Cu₂O, and Cu composites, enhancing the metal-support interaction and facilitating the formation of balanced Cu⁰ and Cu⁺ dual sites as well as high active surface area after reduction. Contributed to the synergetic effect of balanced Cu⁺ and Cu⁰ species proved by density functional theory calculation and the electron-rich CNTs surface, the 40Cu/CNTs catalyst achieved strengthened catalytic performance with methanol yield of 83 %, ethylene glycol yield of 99 % at ethylene carbonate conversion of >99 %, and 150 h of long-term running stability. Consequently, CNTs supported Cu serve as efficient non-silica based catalyst for ester hydrogenation.