Controlled High-pressure Hydrothermal Study Of AuPt And AuPd Bimetallic Nanomaterials

Bimetallic nanomaterials are widely used as catalysts for various chemical reactions due to their excellent catalytic performance, especially Au Pt and Au Pd bimetallic nanoparticles. However, belong to the noble metals, the natural reserves are limited and the prices are costly, no matter Au, Pt and Pd. Therefore, trying to improve the catalytic efficiency and reduce the cost has become one of the most important tasks for researchers to date. Due to the catalytic properties of the bimetallic nanomaterials are decided by the size and shape of the nanoparticles, it is a significant challenge to realize shape-control synthesis of the bimetallic nanomaterials using a simple and efficient method. In this paper, a high-pressure hydrothermal method to controllable synthesized flower-like Au Pt alloy nanoparticles and double-hexagonal-pyramid Au@Pd core-shell nanoparticles was reported for the first time. Meanwhile, the transmission electron microscope(TEM), high-resolution transmission electron microscope(HRTEM), X-ray energy dispersive spectroscopy(EDX) and X-ray diffraction spectrum(XRD) were used to characterize the compositions and morphologies of them. Moreover, the influence of the parameters under the reaction system such as temperature, initial pressure and the concentration ratio of the two kinds of metallic precursors were also studied and explained. The main results of the thesis are showing as follows:1. The flower-like Au Pt alloy nanoparticles were for the first time synthesized by high-pressure hydrothermal method under the condition that chloroplatinic acid(H2Pt Cl6) and chloroauric acid(HAu Cl4) used as precursors, cetyltrimethylammonium chloride(CTAC) served as capping agent and polyvinylpyrrolidone(PVP) as reducing agent. The morphology and size of the nanoparticles could be successfully controlled by adjusting the concentration of CTAC, the initial pressure, the concentration ratio and the total concentration of reactants. Interestingly, the flower-like Au Pt alloy nanoparticles could be transformed to satellite-like nanostructures when the concentration of CTAC was decreased.2. The double-hexagonal-pyramid Au@Pd core-shell nanoparticles were for the first time synthesized by high-pressure hydrothermal method at the presence of chloropalladic acid(H2Pd Cl4), chloroauric acid(HAu Cl4), cetyltrimethylammonium bromide(CTAB) and polyvinylpyrrolidone(PVP). The size and shape of the nanoparticles could be successfully controlled by changing reaction temperature, the initial pressure, the concentration ratio of precursors and the concentration of PVP.