High-pressure Hydrothermal Synthesis And Property Study Of Noble Metal Composite Nanomaterials

With the fast development of modern society,the consumption on energy is rapidly increasing.Fossil fuels?petroleum and coal?which human beings live depend on will not only produce harmful gas after combustion but also face the crisis of regeneration within short time.Compared with renewable resources such as solar,wind and tidal energy,hydrogen energy which owns the advantages of ready availability of reactant,controllable preparation,easy transportation,high yield and little pollution to environment has been attracting public attention.During the hydrogen evolution process,catalyst?especially noble metal catalyst?is helpful to lower the energy barrier.Even though Pt is recognized as the most efficient catalyst in hydrogen production,the broad application is limited heavily because of the expensive price and desperate lack.Reducing the usage of platinum and improving the catalyst efficiency have become the most important problems to solve.This dissertation mainly focused on the preparation of Au@Pd@Pt icosahedron nanoparticles?NPs?and compared them with Pt black on electrocatalytic hydrogen evolution study.Besides that,Au-Pt alloy decahedron NPs were also prepared by high-pressure hydrothermal synthesis,which provides a new route to prepare Pt-based composite materials.The major results of this thesis are introduced as follows:1.Different numbers of platinum submonolayers of Au@Pd@Pt icosahedron NPs(Au@Pd@Pt_{n ML})were prepared by seed-growth method.In the process,the Au@Pd icosahedron NPs were prepared as seeds firstly,cetyltrimethylammonium bromide?CTAB?was served as capping agent and ascorbic acid?AA?as reducing agent.After the extremely slow injection of different concentrations of Na₂Pt Cl₆ precursors,Au@Pd@Pt_{0.3 ML},Au@Pd@Pt_{0.5 ML},Au@Pd@Pt_{0.7 ML}.7 ML and Au@Pd@Pt_{1.0 ML}.0 ML were prepared.Besides that,these Au@Pd@Pt NPs were compared with commercial Pt black on eletrocatalytic hydrogeon evolution.It was found that the current density of Au@Pd@Pt_{0.5 ML}.5 ML is the highest one and the mass activity is around 2-fold of Pt black.Considering the better durability than Pt black,we conclude that Au@Pd@Pt_{0.5 ML}could be regarded as one good HER catalyst.2.The Au-Pt alloy decahedron NPs were synthesized by high-pressure hydrothermal method.Under the condition of cetyltrimethylammonium chloride?CTAC?capping and polyvinyl pyrrolidone?PVP?reduction,chloroauric acid?HAuCl₄?and chloroplatinic acid?H₂PtCl₆?coordinated with ethylene diamine tetraacetic acid precursor solutions?EDTA-Pt?were co-reduced to decahedron-like Au-Pt alloy NPs.The morphology and size of the nanoparticles could be successfully controlled by adjusting the mount of CTAC,PVP,EDTA-Pt and temperature.Meanwhile,the Au-Pt alloy decahedron NPs prepared in different time were tested to speculate the growth process.