Study on Electrocatalytic Properties of Modified Gold Electrodes by Statistical Experimental Strategies

• Main Authors: Li, Yat-June, 李逸鈞
• Other Authors: Wen Ten-Chin
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/22050903286807057428

碩士 === 國立成功大學 === 化學工程學系 === 84 === In this thesis, the electrochemical behavior, oxygen reduction catalytic activity, H2O2 current efficiency, and the electrocatalytic oxidation of organic compounds on modified gold electrode have been investigated.The electrochemical behavior of pure gold and gold deposited titanium electrodes were investigated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques with and without the addition of organics in KOH solutions. CV results reveal that oxygen evolves after the surface saturation with OH/OH-, while organic compounds oxidize in the presence of various Au-OH complexes before the formation of hydroxyl monolayer. LSV results show that benzaldehyde, benzyl alcohol, and ethanol oxidize in the potential range of -0.8~0.2V, -0.6~0.2V, and -0.2 ~ 0.2V, respectively.For oxygen reduction, thermally prepared ternary Ir-Pt-Au electrodes have been investigated experimentally over their entire compositional range using the mixture design method. The results, involving voltammetric charges from electrode redox (q*), oxygen reduction current densities (i), and their correspondingly electrocatalytic activities (i/q*), are examined through regression models and response surface contour plots. Using mixture experimental design, the empirical models are fitted and plotted as contour diagrams which facilitate comparisons with experimental trends noted by other investigators and reveal the synergistic/ antagonistic effects between the mixed oxides. The coefficients of the regression models represented as contour plots were remarkably useful in studying the effects of coating solution on voltammetry charge, oxygen reduction, and electrocatalytic activity. The Pt 50%-Ir 50% binary electrode owns the highest voltammetric charge and the Pt 50%-Au 50% binary electrode possesses the best electrocatalytic activity. Thus, the Ir 33%-Pt 33%-Au 33% ternary electrode is the best electrode for oxygen reduction in alkaline media. By means of fractional factorial design and response surface methodology, the effect of such galvanostatic electrolysis conditions as pH, current density (C.D.), temperature and MgSO4 concentration on H2O2 current efficiencies (C.E.) for Au/graphite electrodes has been systematically investigated. Fractional factorial analysis indicates that the main effects of pH, current density and temperature are key variables influencing the current efficiency on Au/graphite. Through response surface methodology, an empirical equation for H2O2 current efficiencies is fitted and plotted as contour diagrams in order to facilitate examination of experimental results. The contour plots show that a maximum H2O2 current efficiency can be obtained under current density 0.5 mA cm-2 and temperature 18℃ in 1M KOH.The heterogeneous electrocatalytic behavior of gold-platinum electrodes in alkaline medium was investigated with and without ethanol using cyclic voltammetry and potentiodynamic technique. The cyclic voltammetric results showed that Au-Pt binary electrode with 50 mol% Au content in coating solution possessed the maximum apparent activity. The reaction orders with respect to ethanol and OH- concentration were 1.5 and 1, respectively. These results indicated that adsorption of organic compounds on electrode played an important role and Au-Pt binary electrode with 50 mol% Au owns better electrocatalytic activity than that with pure component.