A highly reactive and enhanced thermal stability nanocomposite catalyst based on Pt nanoparticles assembled in the inner surface of mesoporous SiO2 spherical shell

摘要

A synthetic strategy has been developed to encapsulate Pt nanoparticles in heterogeneous catalysts to prevent their sintering. This method involves the preparation of Ptanocarbon spheres composites, the formation of mesoporous silica layers, and finally the removal of CTAB surfactant and NCSs by refluxing and calcination, respectively. TEM images were used to confirm the success of each step, and the catalytic evaluation was tested on the reduction of p-NPh to p-APh monitored by a UV-vis spectra. Besides, the prepared samples were characterized by X-ray diffraction (XRD), N-2 adsorption-desorption isotherms, energy dispersion X-ray analysis (EDX), scanning electron microscope (SEM), and thermogravimetric analysis (TGA) as well. It was found that the encapsulated Pt nanopartides could resist sintering up to 750 degrees C, whereas the catalysts without silica layer protection were shown to sinter by 350 degrees C. When the calcination temperature is 550 degrees C, the obtained materials exhibited the highest catalytic activity. Thus, the hollow sphere structure and the mesoporous silica played a key role in the high catalytic performance. Besides, the sample has an excellent reusability without obvious decrease of the catalytic activities even after five cycles. Finally, a possible mechanism was proposed to explain the well catalytic performance. (C) 2015 Elsevier B.V. All rights reserved.