Preparation And Properties Of Metal Nanoparticles With High Catalytic Activity

As a kind of an efficient conversion device, which can conver the chemical energy toelectrical energy, fuel cells play a significant role in solving the current energy crisis andenvironmental pollution. Fuel cells have numerous advantages, such as high-energy density andlow pollution, so many efforts have been paid to enhance their performance. Due to theirexcellent catalytic activity, noble metal nanomaterials are the main component of electrocatalysts,which are widely used in fuel cells. However, there are many challenges, such as the scarcereserves, the high cost, CO poisoning, and electrocatalysts have important effects on theperformance of fuel cells. Therefore, it is necessary to improve the catalytic activity of a Ptelectrocatalyst. Herein, we focused on preparing platinum nanocatalysts with goodelectrocatalytic properties. The results are as follows:1、 Synthesis of hyperbranched platinum nanocrystals and their electrochemical propertiesHighly dispersed and hyperbranched platinum nanocrystals were successfully prepared inaqueous solution. Chloroplatinic acid (H2PtCl6�'6H2O) was chosen as the precursors to prepareplatinum nanocrystals under a mild condition with poly(vinyl pyrrolidone)(PVP) and L-ascorbicacid as a surfactant and a reductant, respectively. Structural characterization of X-ray powderdiffraction (XRD) and transmission electron microscopy (TEM) revealed that platinumnanocrystals were highly dispersed and hyperbranched morphology with good integrity. Cyclicvoltammetry demonstrated that the highly dispersed and hyperbranched platinum nanocrystalsshowed better activity for methanol oxidation and the current density was1.29mA�'cm-2，which was1.6times more than that of commercial Pt/C catalyst.2、 One-pot synthesis of octahedral platinum nanoclusters with enhanced electrocatalyticactivitiesOctahedral platinum nanoclusters were successfully prepared by one-pot hydrothermalreaction. Chloroplatinic acid (H2PtCl6�'6H2O) was chosen as the precursors to octahedralplatinum nanoclusters under a high temperature and pressure condition with glucose and cetyltrimethyl ammonium bromide (CTAB) as a reductant and a structure-inducing agent, respectively.Structural characterization of transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) revealed that the surfaces of the octahedral platinum nanoclusters werecovered by small platinum nanoparticles uniformly and they were single-crystalline. We studiedthe effects of the structure regulator on properties of products, and the results showed that theappropriate amounts of glucose and CTAB played a key role. Due to the special structure, theoctahedral platinum nanoclusters exhibited a better activity for methanol oxidation than thecommercial Pt/C catalysts, whose mass activity was1.86times greater than that of commercialPt/C, indicating their good potential application in catalysts.3、One-pot Synthesis of three-dimensional dendrite platinum nanocrystalsThree-dimensional dendrite platinum nanocrystals were successfully synthesized via a simpleone-pot hydrothermal reaction. Chloroplatinic acid (H2PtCl6�'6H2O) was chosen as theprecursors to three-dimensional dendrite platinum nanocrystals under a high temperature andpressure condition in the presence of glucose. At high reaction temperature, fructose acted as notonly a reducing agent, but also would form a capping agent simultaneously. Structuralcharacterization of transmission electron microscopy (TEM) and X-ray powder diffraction (XRD)revealed that platinum nanocrystals were three-dimensional dendrite morphology with goodintegrity. Due to its branched structure, three-dimensional dendritic platinum nanoclustersexhibited excellent catalytic activity in the electro-oxidation of methanol, whose mass activity is2.5times than that of the commercial Pt/C.