Synthesis And Catalytic Properties Of Platinum And Palladium Based Nanomaterials

Metal nano materials have attracted many researchers’ attention intensively due to the high catalytic activity, good biological combination,antibacterial performance and so on. There are many synthetic methods for metal nano materials, wherein liquid phase synthesis method is still the main synthesis method. Liquid phase synthesis method is generally divided into two types: oil phase method and aqueous phase method.In recent years, some progress has been made in the synthesis of metal materials with hydrogen.From platinum nano cube and tetrahedron to dendritic nanocrystals, hydrogen has been proven to be an effective clean reductant. For this reason, we synthesized a number of novel nanomaterials with the liquid-phase synthesis at atmospheric pressure and low temperatures in a hydrogen atmosphere.The main research work can be divided into the following areas:(1) Pt dendritic nanocubes were synthesized in pure oleylamine at low temperature and atmospheric pressure. According to the tracking analysis in the process of material synthesis, the dynamic composition of oleylamine and octadecylamine is the key factor for Pt dendritic nanocubes. The platinum precursor was induced to decomposition, nucleation and grow into Pt seeds by hydrogen. The surface of platinum nanocrystals have been continuously updated in the process of the catalytic hydrogenation of oleylamine oleylamine. Thus the surface of as-sythesized platinum nanocrystals is relatively clean. Pt dendritic nanocubes is the preferred catalyst for the porous configuration of the nanocrystals. Subsequently, Pt dendritic nanocubes showed excellent catalytic performance in the hydrogenation of unsaturated hydrocarbons and nitrobenzene. For methanol electro-oxidation reaction, the catalytic activity of platinum dendrites cubic nanometer was 5.3 times greater than platinum nanoparticles.(2) A series of Au@Pt was prepared in pure oleylamine by two-step method in a hydrogen atmosphere. The outer layer with platinum appeared when the surface of gold particles was surrounded platinum.Then the dendritic platinum strips grew on the outer layer. The outer platinum strips catalyzed hydrogenation of oleylamine. The ECSA(electrochemical surface area) of the Au@Pt nanocrystals changed with the renewal process of the platinum surface. Compared with the commercial JM-Pt/C, Au@Pt exhibited better electrocatalytic activity in the oxidation of formic acid and ethanol. The oxidation of formic acid is mainly dehydration process, and the catalytic activity of the prepared Au@Pt nanocrystals was 2 times than the commercial JM-Pt/C for the oxidation of formic acid.(3) The porous Palladium nanospheres were prepared in the pure oleylamine with trans-1,2-cyclohexanedicarboxylic acid and cis-1,2-cyclohexanedicarboxylic acid as the modifying agent. Under alkali conditions, the two catalysts for the hydrogenation of acetophenone show different selectivity. The catalyst modified with cis-1,2-cyclohexanedicarboxylic acid tends to generate phenethyl alcohol and the other catalyst puts emphasis up on ethylbenzene. when NH3·H2O was used, the catalyst selectivity was changed, that is to say the catalyst modified with cis-1,2-cyclohexanedicarboxylic acid tends to generate ethylbenzene.(4) Spongy platinum nanoparticles were synthesized when o-phenylenediamine was added to the oleylamine solution in a hydrogen atmosphere. Silver nanochains were produced with(R)-(+)-1-Phenylethylamine and(S)-(-)-1-Phenylethylamine as the modifying agent. Chiral Au nanowires were prepared when(R)-(+)-1-Phenylethylamine was used. These materials have the potential catalytic applications. Platinum nanocrystals grew fast especially along the 8 pods of Pt NPs. Polyhedral truncated cubic platinum and truncated cubic platinum changed to cubic platinum when the platinum precursor was added to pure oleylamine in a hydrogen atmosphere. Finally,Platinum overgrew on each corner of the cubic platinum. Epitaxial grew of Platinum nanostrips on the suface of Fe Pt rods, Fe Pt NWs and Au NWs. Even when Pd NWs and Ag NWs wered capped by PVP(polyvinylpyrrolidone), Platinum nanostrips also grew on the surface of Pd NWs and Ag NWs. Treatment was used to remove excess PVP on the surface of Pd NWs. PVP-capped Pd NWs broke in the process of UV/O3 treatment.(5) O-halogen aniline is an important chemical intermediate and usually prepared from selective hydrogenation of o-halogen nitrobenzene. But dehalogenation and side effects are the serious problems during the reaction. So the suitable catalyst system has been attracting many researchers. The catalytic system could solve this problem, which is made up of appropriate weak base(Na HCO3 and NH3·H2O) and Pt NPs induced nucleation by Fe(CO)5. The advantage of this system is good catalyst repeatability at a low temperature and atmospheric pressure.