扫描电化学显微镜的数值模拟和距离控制及其应用

Mumeric Simulation and Gap Control of Scanning Electrochemical Microscopy and Its Application

应用反馈模式,结合COMSOL数值模拟,分别考察了步进马达移动距离速率对真实距离、铝合金表面氧化膜状态对逼近曲线以及距离测试误差对典型电化学-化学耦合反应(EC)动力学测试结果的影响。结果表明,正负反馈效应与探针距基底电极距离有关,距离越小,反馈效应越强,同时也与基底电极再生动力学有关。步进马达控制的探针逼近和离开基底电极移动距离与探针真实移动距离的比例分别是0.843和0.568。铝合金表面氧化膜的状态影响逼近曲线从部分正反馈至完全负反馈的变化过程,而步进马达移动引入的距离误差导致EC反应中一级化学均相反应的动力学速率常数误差高达60%。精确距离控制是扫描电化学实验的最基本要求。

Since the gap between the probe electrode and the substrate electrode of scanning electrochemical microscopy（SECM） is not easy to control and clear,based on the feedback model and the COMSOL numeric simulation,the effect of the moving distance of the step motor on the real distance is investigated.The effects of the oxidation film of aluminum alloy on the approaching curve and the test error of the distance on the kinetic parameters of electrochemical-chemical reaction are also investigated.The results show that the positive and negative feedback effect is related to the gap between the probe and the substrate electrode.The smaller the gap,the stronger the feedback effect,while the feedback effect is also impacted by the regeneration kinetics on the substrate electrode.The ratio of the step motorcontrolled distance to the approaching and withdrawing distance from the substrate electrode to the actual moving distance of the tip is 0.843 and 0.568,respectively,which indicates when the stepper motor movement is labeled 1 μm,the actually distances are only 0.843 and 0.568 μm.The state of the oxide film on the surface of aluminum alloy affects the approaching curve from partial positive feedback to pure negative feedback,and the distance error of stepper motor movement leads to the error of chemical homogeneous reaction rate constant in EC reaction as high as 60%.Precise gap control is the fundamental for scanning electrochemical microscopy experiments.