葡萄糖、半乳糖和乙醇恒电流氧化过程电位振荡的EQCM研究

采用电化学石英晶体微天平(EQCM)研究了0.5 mol•L^-1 NaOH水溶液中铂电极上葡萄糖、半乳糖和乙醇恒电流氧化过程中伴随的电位振荡行为. 两个糖体系的电位振荡过程伴随EQCM频率的同步振荡响应, 而乙醇体系中相应的频率响应却非常小；三个体系振荡过程的同步动态电阻响应均很小, 表明振荡过程频率响应主要为质量效应. 虽然葡萄糖和半乳糖结构相似, 电位和频率振荡的幅度相当, 但频率波数和周期明显不同, 表明电位振荡行为对两者呈现良好的分子识别能力. 本文也讨论了相关振荡机理和NaOH浓度效应及碱性介质中铂电极电化学过程, 提出了所形成的铂氧化物主要是PtO₂-3H₂O_ad以及两糖体系振荡过程中糖酸根阴离子伴随着高/低电位在铂电极上吸/脱附的新观点.

EQCM Study on the Potential Oscillations during Galvanostatic Oxidation of Glucose,Galactose and Ethanol

Galvanostatic oxidation of glucose, galactose and ethanol at platinum electrodes in 0.5 mol•L^-1 aqueous NaOH and accompanying potential oscillation behaviors were comparatively studied by the electrochemical quartz crystal microbalance(EQCM) method. The EQCM-frequency oscillation was synchronously observed for the two saccharide systems during their potential oscillations, but it was negligibly small for the ethanol system, and the responses of the motional resistance were minor for all systems, suggesting that the mass effect governed the EQCM frequency responses. Although glucose and galactose are very similar in chemical structure and the amplitude for potential or frequency oscillation was roughly equivalent for both systems, the wave numbers and periods were obviously different from each other, implying that the electrochemical oscillation possesses high molecular recognition between the two systems. Related oscillation mechanism, the effect of NaOH concentration on oscillation, and the electrochemical process of platinum electrode in aqueous NaOH were also discussed. It was concluded that the platinum oxide formed here was mainly PtO₂-3H₂O_ad, and the potential oscillations for the two saccharide systems were accompanied with the adsorption/desorption of anions of saccharic acids at high/low potentials on platinum.