Study On Synthesis Of Platinum Nanoparticles And Their Self-Assembled Films On The Surface Of Iron Electrode

This thesis mainly focused on the synthesis of platinum nanoparticles. Well dispersed platinum nanoparticles and those with special shapes were synthesized through electrochemical and thermochemical methods. TEM, HRTEM, UV-Vis, IR, SEM, XRD were employed to characterize the synthesized nanoparticles. Attempts were made to assemble the platinum nanoparticles to the iron surfaces. And electrochemistry measurements such as EIS, polarization curves were used to characterize the assembled films. The main research results are as following:1. Well dispersed platinum nanoparticles were synthesized in aqueous solution through electrochemical reduction under the protection of PVP. The absorption plasmon of the initial H₂PtCl₆ solution centered at 262nm which disappeared after the reaction, demonstrating the formation of platinum nanoparticles. The effects of reaction time and PtCl₆^2- concentration on the formation of the Pt nanoparticles were studied. The protection mechanism of PVP during the Pt nanoparticles formation was also discussed. TEM, IR, UV-Vis were used to characterize the products. Results indicated that PVP plays an important role in the formation of platinum nanoparticles. Well-dispersed Pt nanoparticles were obtained when the concentration of PVP was increased.2. Platinum nanoparticles were synthesized under the different chemical reduction agents. H₂PtCl₆ was reduced by NaBH₄ under room temperature and icy cold water, respectively. TEM results showed that the particles obtained at icy cold water exhibits better dispersion than those obtained at room temperature. Mild reduction agent sodium citrate was used to synthesize Pt particles through thermal process. The products were well dispersed and the HRTEM images of the small particles presented clear lattice fringes with the interfringe distance measured to be 0.23nm, which well corresponds to the lattice spacing of the {111} plane. Direct thermal reduction of H₂PtCl₆ by PVP was also used to synthesize platinum nanoparticles. TEM characterization indicated that the products took on some morphologies such as cubic, dendrites, nanocages. The HRTEM characterization of nanocages showed the edge of the nanocage exhibited clear lattice fringe. The co-existing small particles also presented clear lattice finge. Both interfinge distances were measured to be 0.23nm, corresponding to the lattice space of the {111} plane. PVP worked both as reducing agent and protection agent. Its mechanism during the Pt nanoparticles was discussed.3. We found that platinum nanoparticles tended to be immobilized on the ITO glass to form order structures after SEM characterization of the ITO glass immersed in the platinum nanoparticles solution. Attempts were made to assemble the platinum nanoparticles to the iron electrode surface. Electrochemical measurements such as EIS, polarization curves were employed to characterize the self-assembled films. Results indicated that iron electrode covered with Pt particles films were more easy to corrode in H₂SO₄, which may due to the strong catalytic property of the Pt nanoparticles.