High-pressure Hydrothermal Controlled Synthesis Of Platinum Group Metallic Nanomaterials

Platinum group metallic nanomaterials, especially platinum and palladium nanomaterials,have attracted increased attentions because of their good catalytic performances, which arewidely used in industrial catalytic and laboratorial catalytic reactions. However, platinumgroup metals belong to precious metals, the low storage and high cost of which limit theirapplications. Therefore, it is important to improve their catalytic efficiency and lower cost. Itis well known that catalytic properties of platinum group metallic nanomaterials are decidedby their sizes, shapes and crystalline facets. Therefore, it is of significant importance to realizecontrollable synthesis of platinum group metallic nanomaterials by a simple, efficient andenvironmental friendly method. In this thesis, we reported a high-pressure hydrothermalmethod to the controllable synthesis of platinum nanoflowers and palladium nanodecahedrons,which were characterized by transmission electron microscope (TEM), high-resolution TEM(HRTEM), X-ray energy dispersive spectroscopy (EDX) and X-ray diffraction spectrum(XRD). Meanwhile, reaction parameters such as pressure, temperature and reactantconcentrations were also studied and therefore put forward a primary growth model to explaingrowth mechanisms of the platinum nanoflowers and palladium nanodecahedrons. The majorresults of this thesis are as follows:1. Platinum nanoflowers were synthesized by high-pressure hydrothermal method, inwhich potassium chloroplatinite (K2PtCl4), potassium iodide (KI) and polyvinylpyrrolidone(PVP) were used as precursors, complexing reagent and capping agent and reducing reagents,respectively. The resulting platinum nanoflowers had uniform size, single-crystalline structureand high yield; the sizes and shapes of platinum nanoflowers could be effectively controlledthrough varying systematic pressure and KI and PVP concentrations.2. Palladium nanodecahedrons were also synthesized by high-pressure hydrothermalmethod, in which palladium chloride (PdCl2), potassium bromide (KBr), iron chloride (FeCl3)and polyvinylpyrrolidone (PVP) were used as precursors, complexing reagent, selectivereagent of crystalline facets and capping agent and reducing reagents, respectively. Thepalladium nanodecahedrons had uniform size, multiple-twinned structure and high yield. Thesizes and shapes of palladium nanodecahedrons could be well tailored through varying temperature and KBr and FeCl3concentrations.3. Through studying the relationship between systematic pressure and temperature, theinside temperatures of the high-pressure reactions could be real-time monitored, which couldbe helpful to explain the pressure-depended growth mechanism of the size-andshape-controlled synthesis.