Controllable decoration of palladium sub-nanoclusters on reduced graphene oxide with superior catalytic performance in selective oxidation of alcohols†
Nowadays, it is widely recognized that the performance of many catalytic materials is closely related to their particle size; however, it is still a great challenge to produce metal particles on a sub-nanoscale at low cost and in a facile way. In this work, uniformly dispersed palladium sub-nanoclusters were controllably decorated on reduced graphene oxide (Pd/rGO) by a facile modified impregnation method without using any protecting agents; a mean palladium cluster size of as low as 0.7–0.9 nm can be achieved by impregnation with PdCl2 as the precursor, ethanol or acetone as solvent and calcination in hydrogen at low temperature. The Pd/rGO catalyst exhibits high activity in the aerobic oxidation of benzyl alcohol, with almost a complete alcohol conversion and selectivity of 100% to benzaldehyde at 60 °C; moreover, it also displays much higher stability against deactivation from the aggregation of Pd particles than the Pd catalyst with active carbon as the support. The superior performance of the Pd/rGO catalyst can be ascribed to the small size and high valence of Pd sub-nanoclusters and the coordination of chloride ions, as well as the strong interaction between Pd species and the rGO support, as demonstrated by various characterization measures. These results help to clarify the relationship between the preparation, structure and performance of the supported Pd/rGO catalyst in the selective oxidation of alcohols, which brings forward an effective approach to obtain metal sub-nanoclusters on rGO with superior catalytic performance.