COMBINATION OF SCANNING ELECTROCHEMICAL MICROSCOPY AND LOCAL ELECTROCHEMICAL IMPEDANCE METHOD

结合扫描电化学显微镜（SECM）和局部电化学阻抗法（LEIM）、扫描液滴电池（SDC）、液相离子枪等微电化学技术，在几μm ~几十μm尺度上对金属和溶液界面上电化学反应的非均质性进行了评价。此外，为了获得更精确的探头电流图像，改进了SECM的性能。得到了以下结果：将用于SECM的微圆盘铂电极与用于LEIM的微铂黑电极相结合。采用嵌入环氧树脂中的铂箔作为模型试样电极。尽管LEIM的横向分辨率是SECM.2的几十倍，但SECM和LEIM图像都能清晰地分辨出铂箔和环氧树脂。SDC与SECM相结合，在SDC中，电解质溶液可以在样品电极表面扫描。用SDC法测定了多晶金电极的伏安谱和阻抗谱，结果表明，多晶金电极的晶粒均具有（111）取向，但方位角不同。用SDC在钛电极表面形成局部阳极氧化膜。用SECM.3可以评价阳极氧化膜的局部形成情况。采用一种覆盖氯化银的微型银电极作为SECM探针电极。利用微电极的阴极极化可以局部生成少量氯离子，称为“液相离子枪”。液相离子枪成功地诱导了铁电极上钝化膜的局部击穿。引发局部击穿所需氯离子的临界量取决于成膜条件、膜内电场和溶液pH。通过检测阳极极化过程中钛电极与成膜过程平行放出的氧，测量了钛电极在硫酸溶液中的探针电流图像。该探针电流图像与采用亚铁氰化物离子氧化还原体系作为介质的传统SECM测量得到的探针电流图像一致。探针电流图像与光学显微照片的对比表明，析氧的非均匀性取决于衬底钛的晶体取向，析氧优先发生在较薄的钝化膜或较高给体密度的膜上。少

The combinational use of scanning electrochemical microscopy (SECM) and other micro-electrochemical techniques, such as local electrochemical impedance method (LEIM), scanning droplet cell (SDC) and liquid-phase ion gun, was attempted to evaluate the heterogeneity of electrochemical reaction at the metal and solution interface in a scale of several μm to several ten μm. Furthermore, the performance of SECM was improved to obtain the more precise probe current images. The following results were obtained.1. Micro-disk platinum electrode for SECM was combined with micro-platinum black electrodes for LEIM. A platinum foil embedded into epoxy resin was used as a model specimen electrode. Both SECM and LEIM images could distinguish clearly between the platinum foil and epoxy resin although the lateral resolution of LEIM was several ten times as much as that of SECM.2. SDC, in which a droplet of electrolyte solution can be scanned over the specimen electrode surface, was combined with SECM. T … More he voltammetry and impedance spectra of a polycrystalline gold electrode measured with SDC have revealed that all grains have a (111) orientation but different azimuth angles. SDC was also applied to form locally anodic oxide films on titanium electrode surface. The local formation of anodic oxide film could be evaluated by SECM.3. A micro silver electrode covered with silver chloride was employed as a probe electrode of SECM. A small mount of chloride ions could be generated locally with a cathodic polarization of the microelectrode, which was named "liquid-phase ion gun". The use of liquid-phase ion gun succeeded in inducing the local breakdown of passive film on iron electrode. The critical amount of chloride ions needed for initiating the local breakdown depended on the film formation conditions, the electric field in film, and pH of solution.4. The probe current image of titanium electrode in sulfuric acid solution was measured by detecting oxygen which evolved from the electrode in parallel with film formation during anodic polarization. This probe current image coincided with the probe current image obtained with the conventional SECM measurement in which the redox system of ferrocyanide ions was employed as a mediator. Comparison between the probe current images and optical micrograph has indicated that the heterogeneity of oxygen evolution depends on the crystallographic orientation of the substrate titanium and the oxygen evolution takes place preferentially on the thinner passive film or the film with the higher donor density. Less