文摘
The Pt/CeO2 nanocomposites of Pt nanoparticles partially confined in the mesopores of microsized mesoporous CeO2 (1.0% Pt/CeO2-MM) or supported on the surface of CeO2 nanocubes (1.0% Pt/CeO2-NC) with the same Pt loading of 1.0 wt % were prepared by the impregnation of microsized mesoporous CeO2 or CeO2 nanocubes with Pt(NO3)2 aqueous solution, followed by the reduction with NaBH4 aqueous solution. 1.0%Pt/CeO2-MM exhibits much higher catalytic activity for benzene oxidation than 1.0%Pt/CeO2-NC. Compared to 1.0% Pt/CeO2-NC, the reaction temperatures of T50 and T90 (corresponding to a benzene conversion = 50% and 90%) for 1.0% Pt/CeO2-MM tremendously decreases by ΔT50 = 149 °C and ΔT90 = 196 °C, respectively. The turnover frequency (TOF) of 1.0% Pt/CeO2-MM at 140 °C increases by 9.0 times as compared to that of 1.0% Pt/CeO2-NC. The tremendous enhancement in the catalytic activity is due to a novel metal support interaction in 1.0% Pt/CeO2-MM. The novel metal support interaction is theoretically studied by density function theory (DFT) calculation and experimentally studied by CO-TPR, CO-TPD, H2 pulse titration, and HRTEM. The theoretical and experimental evidence reveal that the partial confinement of Pt nanoparticles in the mesopores of microsized mesoporous CeO2 leads to a significant enhancement in the activity of the surface lattice oxygen around the interface between Pt nanoparticles and CeO2, thus tremendously increasing the catalytic activity.