ZrO2-x modified Cu nanocatalysts with synergistic catalysis towards carbon-oxygen bond hydrogenation

Abstract

Carbon-oxygen bond hydrogenation serves as a versatile fundamental reaction extensively applied in chemicals synthesis, but rational design of heterogeneous catalysts with satisfactory catalytic performance and stability remains a big challenge. Herein, a ZrO2-x modified Cu nanocatalyst with unique interfacial structure Cu-O-Zr3+-Vö (Vö denotes oxygen vacancy), was elaborately designed and prepared via a facile in situ structural transformation from layered double hydroxide precursors, confirmed by a comprehensive study including HADDF-STEM, in situ EXAFS and quasi in situ XPS measurements. The optimized catalyst (Cu/ZrO2-x-S3) exhibits an extremely high catalytic performance toward dimethyl oxalate (DMO) hydrogenation to ethylene glycol (EG), with a yield of 99.5 %. Notably, the turnover frequency (TOF) value and space time yield of EG reach up to 42.4 h−1 and 1.05 gEG⋅gcat−1⋅h−1, respectively. This is, to the best of our knowledge, the highest level compared with previously reported Cu-based catalysts under similar conditions. In addition, the in situ investigations (in situ DMO-FTIR, in situ DMO-EXAFS) and catalytic evaluations substantiate interfacial sites serve as active center: the Zr3+-Vö facilitates adsorption and activation of CO/CO groups; whilst H2 molecule undergoes dissociation at the interfacial Cu species, followed by hydrogen spillover onto Cu-O-Zr for hydrogenation of activated CO/CO bonds. This interfacial synergistic catalysis offers a new reaction pathway with decreased activation energy, accounting for the resulting superior catalytic performance, which can be extended to other carbon-oxygen bonds hydrogenation systems.