Gold Sols Preparation Using Methanol and Citrate and Test Its Electrochemical Activity

• Main Authors: Yu-Yin Lin, 林俞吟
• Other Authors: Shawn-Dian Lin
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/81927514714374152399

碩士 === 元智大學 === 化學工程與材料科學學系 === 95 === This study uses citrate - methanol to prepare gold sols from AuCl3 and their electrocatalytic activities toward oxygen reduction reaction (ORR) and CO oxidation are analyzed. Rotating Disk Electrode (RDE) is used to illustrate the effect of mass transfer on the measured electrocatalytic activity. The activity of gold is compared to that of platinum electrode. Experimental results show that AuCl3 precursor cannot be reduced to gold nanoparticles with methanol alone, but sodium citrate by itself can reduce AuCl3 at 60℃ to obtain a ruby(wine-red) color sols with an average size of 21 nm. Using both methanol and sodium citrate, stable purple-color sols can be obtained with a higher aspect ratio and the average size is around 35 nm. When the citrate concentration is increased, the sol color turns to dark-purple, the average particle increases, and the stability decreases. In ORR tests, Au sols show a lower onset potential than Au disk electrode; the same phenomena is found when Pt black is compared to Pt disk. The per-gram electrocatalysis ORR activity of Au sols increases with decrease of particle size, but the aspect ratio did not show a significant influence on the ORR activity. In CO oxidation tests, Pt catalysts show oxidation activity to both strongly adsorbed CO and CO dissolved in solution at 0.85-1.0 and 1.0-1.4 V respectively. The former current seems dependent on the CO concentration while the latter seems dependent on the surface hydroxyl concentration. Gold electrodes have a relatively weak CO oxidation at 1.05 V attributable to adsorbed CO, and oxidation currents attributable to solution phase CO at 1.23-1.36 V. The results indicate that Au nanoparticles are active for ORR and CO oxidation in acidic electrolyte but its activity is lower than Pt.