电镀铂/金的金电极上As(Ⅲ)电化学行为的电化学石英晶体微天平研究

An Eletrochemical Quatrz Crystal Microbalance Study on Electrochemical Behavior of As(Ⅲ) at Au/Au and Pt/Au Electrodes

采用电化学石英晶体微天平(EQCM)技术研究了Britton-Robinson(B-R,pH=1.8～11.2)缓冲溶液和H2SO4介质中电镀铂/金的金电极上As(Ⅲ)的循环伏安行为。通过实时监测EQCM频率等参数的变化过程并利用预电沉积As(0)放大电极响应信号,考察了两电极上As(0)的电沉积、As(Ⅲ)和As(Ⅲ)组分的吸附特性以及As组分电化学行为的pH依赖性。主要结论如下:(1)As(0)在两电极表面均可电沉积,但在镀铂金电极上更明显,且足量电沉积的As(0)的电氧化过程出现外/内层As(0)依次氧化的两个电流峰;(2)As(Ⅲ)在镀铂电极上可强烈吸附,且被氧化成As(Ⅲ)时解吸,而镀金电极上As(Ⅲ)和As(Ⅲ)的吸附能力均很弱;(3)在pH=1.8的B-R缓冲溶液和0.1 mol/L H2SO4介质中,镀铂/金电极上As(Ⅲ)的电催化氧化电流趋于最大。通过As(Ⅲ)在镀铂/金电极上的吸附预富集和随后的电催化氧化溶出,提出了高敏检测As(Ⅲ)的线性扫描伏安法,检测灵敏度提高约40倍。

Electrochemical behavior of As（Ⅲ） at Au/Au and Pt/Au electrodes was investigated with an electrochemical quartz crystal microbalance（EQCM） in Britton-Robinson（B-R,pH=1.8-11.2） buffer solutions and in 0.1 or 0.5 mol/L aqueous H2SO4.Through real-time process monitoring of the EQCM parameters（frequency etc.） and enhancement of the electrode-response signals by pre-electrodeposition of As（0）,the electrodeposition of As（0）,the electrode-surface-adsorption characteristics of As（Ⅲ） and As（Ⅲ）,and the pH-dependence of the electrochemistry of As species were investigated.The following main conclusions are reached：（1） electrodeposition of As（0） can occur on both electrodes,but electrodeposition of As（0） on Pt/Au is more significant,and the electrooxidation of As（0） electrodeposited on Pt/Au at sufficient quantity can exhibit two current peaks for oxidation of outer-layer As（0） followed by inner-layer As（0）;（2） As（Ⅲ） can strongly adsorb on Pt/Au but its oxidation product as As（Ⅲ） can desorb from the electrode surface,and the adsorption of both As（Ⅲ） and As（Ⅲ） is very weak on Au/Au;（3） the electrooxidation current of As（Ⅲ） on Pt/Au tends to be the maximum in pH=1.8 B-R buffer solution and in 0.1 mol/L aqueous H2SO4.Based on the pre-adsorption of As（Ⅲ） on Pt/Au and its catalyzed electrooxidation stripping,we proposed a new linear sweep voltammetric electroanalysis method for the determination of As（Ⅲ）,by which the detection sensitivity for As（Ⅲ） can be 40-fold enhanced over the pre-adsorption-free case