Gollas B, Bartlett P N, Denuault G
Department of Chemistry, University of Southampton, Highfield, United Kingdom.
Anal Chem. 2000 Jan 15;72(2):349-56. doi: 10.1021/ac990796o.
A novel combination of an electrochemical quartz crystal microbalance (EQCM) and a scanning electrochemical microscope (SECM) has been built. Unlike conventional EQCMs, the instrument described here allows rapid in situ measurement of the modulus of the quartz crystal's transfer function. Data analysis in the complex plane for the Butterworth-Van Dyke (BVD) equivalent circuit yields the real and the imaginary components R (damping resistance) and XL (reactive inductance) of the crystal's electroacoustic impedance around its resonant frequency of 10 MHz. The influence of different tip shapes of an approaching microelectrode on the electroacoustic impedance of the quartz crystal was studied and found to be minimal for certain geometries. The capability of the EQCM/SECM instrument was tested in cyclic voltammetric plating/stripping experiments using a copper(I) chloride solution of high concentration in 1 M HCl. Four parameters, XL, R, the substrate, and the tip current, can be recorded simultaneously. Depletion layer effects were observed and could be corrected for to yield accurate current efficiencies for potentiodynamic and potentiostatic copper plating. The amperometric response of the SECM tip positioned closely to the substrate reflects the concentration changes of electroactive ions in the diffusion layer of the substrate electrode.
已构建了一种将电化学石英晶体微天平（EQCM）和扫描电化学显微镜（SECM）相结合的新型仪器。与传统的EQCM不同，此处描述的仪器能够对石英晶体传递函数的模量进行快速原位测量。针对巴特沃斯 - 范戴克（BVD）等效电路在复平面内进行数据分析，可得出晶体在其10 MHz谐振频率附近的电声阻抗的实部和虚部R（阻尼电阻）和XL（电抗电感）。研究了接近的微电极的不同尖端形状对石英晶体电声阻抗的影响，发现对于某些几何形状，这种影响极小。在使用1 M HCl中高浓度氯化亚铜溶液进行的循环伏安电镀/剥离实验中测试了EQCM/SECM仪器的性能。可以同时记录四个参数，即XL、R、基底和尖端电流。观察到了耗尽层效应，并可对其进行校正，以获得恒电位和恒电流镀铜的准确电流效率。紧邻基底放置的SECM尖端的安培响应反映了基底电极扩散层中电活性离子的浓度变化。
