The interfacial oxygen-defective sites of oxide-supported metal catalysts are generally regarded as active centers in diverse redox reactions. Identification of their structure-property relationship at the atomic scale is of great importance but challenging. Herein, a series of La3+-doped three-dimensionally ordered macroporous CeO2 (3D-Ce1-xLaxO2-δ) were synthesized and applied as supports for Pt nanoparticles. The pieces of evidence from a suite of in-situ/ex-situ characterizations and theoretical calculations revealed that the La3+-mono-substituted La-□(-Ce)2 sites (where □ represents an oxygen vacancy) exhibited superior charge transfer ability, behaving as trapping centers for Pt nanoparticles. The resulting interfacial Ptδ+/La-□(-Ce)2 sites served as the reversible active species in the aerobic oxidation of 5-hydroxymethylfurfural to boost catalytic performance by simultaneously promoting oxygen activated capacity and the cleavage of O-H/C-H bonds of adsorbed hydroxymethyl groups. Consequently, the Pt/3D-Ce0.9La0.1O2-δ catalyst possessing the highest number of Ptδ+/La-□(-Ce)2 sites showed the best catalytic performance with 99.6% yield to 2,5-furandicarboxylic acid in 10 h. These results offer more insights into the promoting mechanism of interfacial oxygen-defective sites for the liquid-phase aerobic oxidation of aldehydes and alcohols.
Keywords: 5-hydroxymethylfurfural; La3+-doped CeO2; catalytic oxidation; interfacial asymmetric oxygen vacancy; structure-performance relationship.