Preparation Of Platinum-based Nanoparticles And Their Catalytic Performance

Pt and Pt-based nanoparticles have attracted more and more attention because of their good catalytic activity in lots of fields. However, the cost of Pt is extremely high just because its rare storage in the earth. Therefore, most efforts have focused on reducing Pt utilization and increasing its catalytic activity. Among them, addition of one or more element in Pt electro-catalysts followed by the proper shape control has been considered to be the most promising strategy to synthesize more efficient Pt-based catalysts. In this dissertation, we will discuss the structure and catalytic activity of various composite including bimetallic Pt/Ru nanoparticles, Pt-Fe2O3/GO nanomaterial and CoCr2O4 nanoparticles, to establish a structure-activity relationship between the structure and properties of catalyst. To this purpose, we used a combination of X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The works are exhibited as follows in detail:1. Bimetallic Pt/Ru nanoparticles with different Pt/Ru molar ratios were synthesized by a solvothermal method and characterized by various methods. Our observations revealed that these Pt-Ru nanoparticles have a Pt-rich core and a Ru-rich shell structure. After annealing at 500℃, the alloying extent of Pt/Ru nanoparticles increased, a portion of Pt atoms migrated to surface, and most of the surficial oxidized Ru atoms were reduced and involved in alloying. The evaluations of methanol electro-oxidation activity elucidated that electro-catalytic performance improved with the increasing oxidation degree of superficial Ru atoms.2. Pt-Fe2O3/GO nanocomposite was synthesized by one-pot hydrothermal method, in the absence of any other oxidant and reductant. On one hand, GO can serve as an oxidant, corresponding to the oxidation of Fe+ to Fe2O3, on the other hand, reduction of Pt4+ to Pt as a reductant. The characterization results showed that the obtained Pt-Fe2O3 nanoparticles distributed on GO uniformly, the average size of these nanoparticles is about 40-50 nm. Subsequent evaluations of the catalytic activity for photocatalytic degradation of organic dyes proved that, Pt-Fe2O3/GO is a good catalyst for photocatalytic degradation of MB. The most likely reason is that the interaction between Pt, Fe2O3 and GO, which decreases the combination of photo-induced electrons with holes, allowing more electrons and holes migrate to the surface of the catalyst to produce more radicals with strong oxidizing, thereby improving photocatalytic performance of the catalyst for degradation of MB.3. Spinel compound CoCr2O4 was synthesized by a hydrothermal and post-calcined method, then, combined with multi-walled carbon nanotube. The corresponding test results showed that the spinel structure of samples remained unchanged after annealing at different temperature in the air. However, the degree of crystallinity and the size of the samples increased with the annealing temperature. The evaluations of oxygen evolution reaction activity demonstrated that the catalytic performance of the catalysts declined while annealing in the air. Moreover, the electro-catalytic performance of the catalyst improved at some degree after combining CoCr2O4 with carbon nanotube (CNT).