Synergistic effects of bimetallic PtRu/MCM-41 nanocatalysts for glycerol oxidation in base-free medium: Structure and electronic coupling dependent activity

Abstract Bimetallic PtRu catalyst was first reported for oxidation of glycerol to glyceric acid in base-free medium using O2 as the oxidant. A combination of density functional theory (DFT) calculations and multi-characterizations (e.g., H2-TPR, HAADF-STEM and XPS) revealed that the strong interaction between Pt and Ru could promote the dispersion of PtRu alloy nanoparticles and enhance the electronic coupling effect on the metal surface. Meanwhile, compared to the monometallic Pt catalyst, the introduction of Ru contributes to the direct dissociation of molecular oxygen and water to hydroxyl group, leading to the excellent catalytic activity. A volcanic-shaped relationship between Ru/Pt ratio, catalytic performance, structure-sensitivity and electronic coupling effect was systematically established. Furthermore, the role of structure-sensitivity and electronic coupling effect for the enhanced catalytic activity of PtRu catalysts with different Ru/Pt ratios are distinguished in detail. Finally, the Pt0.8Ru0.8/MCM-41 catalyst showed excellent catalytic activity (TOF: 823.9 h-1), glyceric acid selectivity (80.1%) and stability (recycling for 5th) under the optimized conditions (80 °C, 1 MPa O2 and 12 h). The insights and methodology reported here may pave the way to the rational design of bimetallic catalysts for efficient conversion of bio-derived substrates under mild conditions.