On the effect of process parameters for synthesizing Pt nanoparticles and Pt/C catalysts by alcohol reduction method

• Main Authors: Shin-Ru Wang, 王馨如
• Other Authors: 曾文甲
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/42853204600192277535

碩士 === 國立中興大學 === 材料工程學系所 === 95 === The objective of this research is to use ethanol as a reducing agent to replace commonly-used ehthylene glycol in the reduction process of hexachlorplatinic acid into Pt nanoparticles with the presence of polyvinylpyrrolidone (PVP) as a surfactant to prevent the Pt nanoparticles from agglomeration. Dispersion stability and particle size of the Pt nanoparticles in solutions and on carbon blacks were examined by changing the process parameters of reaction temperature (35~95oC), PVP concentration (0.011~0.66g), ethanol fraction (0.2~0.9), and oxidation treatment of carbon blacks by UV-visible,TEM,XRD,TGA/DTA,FT-IR and BET analyses. This research showed that reduction rate and dispersion stability of the Pt nanoparticles in solutions increased with reaction temperature. TEM results indicated that the dispersion of Pt colloidal solution was improved apparently with the increase of the molar ratio of PVP monomeric unit/Pt. When the molar ratio of PVP monomeric unit/Pt was equal to or greater than 40, the dispersion of Pt colloidal solutions seemed to reach a stable state. XRD results showed that the volumetric fraction of ethanol affected grain size of the synthesized Pt. When the molar ratio of PVP monomeric unit/Pt is kept constant at 1, the Pt grain size appeared to increase with the volumetric fraction of ethanol at the low PVP concentration. On the contrary, the Pt grain size reduced with more PVP concentration when the molar ratio of PVP monomeric unit/Pt was 40. From FTIR-ATR analysis, the number of the oxygen surface functional group on carbon blacks was increased by raising the concentration of hydrogen peroxide (H2O2) at high temperature (90 oC). TEM observation revealed that the carbon blacks after surface-oxidation treatment adsorbed more Pt particles. BET surface area of the Pt/C catalysts decreased from 146 to 92 m2/g after the surface oxidation treatment. For the synthesis of Pt/C catalysts with an improved dispersion stability and grain size, use of 0.8 or greater than 0.8 ethanol volumetric fraction in this study appears to attain Pt particles dispersed more uniformly in carbon blacks with a cluster size mostly less than 10nm. But there is still a substantial amount of Pt loss, which remains as a problem needed to be solved in future works.