Nanocasting synthesis of an ordered mesoporous CeO2-supported Pt nanocatalyst with enhanced catalytic performance for the reduction of 4-nitrophenol

Abstract

Ordered mesoporous ceria (meso-CeO₂) was fabricated by nanocasting employing Ia3d mesoporous silica KIT-6 as the template. For comparison, ceria nanoparticles (nano-CeO₂) with non-ordered mesoporous were also synthesized via a sol–gel method. Polyamidoamine (PAMAM) dendrimers were used as stabilizing agents to prepare a dispersed Pt nanoparticle colloidal solution. Afterward, the obtained well-dispersed Pt nanoparticles were immobilized on meso-CeO₂ and nano-CeO₂, respectively. The prepared samples were characterized through several techniques, such as X-ray diffraction (XRD), nitrogen adsorption–desorption isotherms, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and energy dispersion X-ray analysis (EDX) with mapping. The results revealed that the as-prepared meso-CeO₂ has high crystallinity, a relatively small crystalline size, a well-ordered mesoporous structure and high surface area of 115.3 m² g⁻¹. In addition, the Pt/meso-CeO₂ catalyst showed relatively uniform distribution of Pt nanoparticles with small sizes (∼4 nm). The catalytic performances of the as-synthesized catalysts were evaluated relying on the reduction of 4-nitrophenol monitored by UV-vis spectra. It was found that Pt/meso-CeO₂ exhibited better catalytic activity compared with Pt/nano-CeO₂. Besides, Pt/meso-CeO₂ possessed good reusability and maintained a conversion of no less than 90% even after five cycles.