Manipulating Pt-ZnO interface for fast selective oxidation of glycerol to glyceric acid in base-free medium

Abstract

Fine constructing the desirable active sites of catalysts is critical for the efficient polyol oxidation. Herein, we conceptually manipulate the Pt-ZnO interfacial active site instead of traditional Pt-Pt active site to isolate oxidation reaction and carboxylic acid desorption for fast selective oxidation of glycerol to glyceric acid in base-free medium. Multiple characterizations (including in-situ spectroscopy, reaction kinetics and density functional theory calculation, etc.) revealed that the strong electronic delocalization of Pt d-partial and the synergistic effect of ZnO adsorption could collectively strengthen the adsorption of glycerol and then promote the C-H bond of RCH₂O intermediate in the primary hydroxyl group oxidation, resulting in higher catalytic activity over the Pt-ZnO interface. Meanwhile, the abundant oxygen vacancy of well-dispersed nano-ZnO could preferentially adsorb the formed glyceric acid product, preventing the coverage of the efficient Pt-Pt and Pt-O-Zn active sites by carboxylic acid products. Such tailored interface strategy achieves 80.4 % glycerol conversion and 84.6 % glyceric acid selectivity in only 1 h, and the turnover frequency could also be as high as 1338.4 h⁻¹ over the optimal Pt/ZnO-MCM-41 (200) catalyst. The methodology provided here constitutes a promising basis for highly efficient polyol oxidation catalysis under mild and green conditions.