The Construction And Application Of High Frequency Alternating Current Heated Microelectrode Technology

The influence of temperature on the kinetics of electrode process cannot be ignored since it can affect the electrochemical reaction rate, reaction potential of oxidation/eduction and mass transfer rate and absorption desorption of reactant. Traditional methods of the modulation of temperature include overall heating by water bath or electric heating equipment. However, the overall heating approach requires thermostatic apparatusand specially designed cell. Changing the temperature and keeping temperature constant are relatively slow and unstable. Organic solution when heated is volatile and does harm to human body. Many electrochemical reactions in the water solution can’t be studied above the boiling point of water. Many methods have been developed to raise the temperature of the working electrode or the thin layer near the solution the working electrode, which include beam heating method, radio frequency heating method, microwave heating method, high-frequency alternating current heating method. In the above mentioned techniques, high frequency alternating current heated technology is simple and can quickly adjust the temperature of microelectrode. In this research paper high-frequency alternating current heated disk microelectrodes technology were set up, which combined with Scanning Electrochemical Microscope (SECM) or with laser confocal raman microspectroscopy technology. The main contents and result are listed as follows:1. The theoretical analysis, design, processing and debugging for high frequency alternating current heating circuitThe analysis of equivalent circuit was carried out. Printed circuit board are designed, processed, and debugged. The effect of wiring and heating power are studied preliminarily, which have an effect on heating. The results show that heating effects of matching impedance circuit board with microstripes is one of the best choice. Under the same frequency, the higher the heating power, the shorter the electrode is connected to a PCB wiring, the better is the heating effect.2. The construction of high frequency alternating current heating system and electrochemical behavior of Fe(CN)63-/4-at different temperatureA new type of thermocouple microelectrode was employed. This electrode can be used to be heated and measure the temperature on the surface of the electrode simultaneously. The dependence of electrochemical behavior on the temperature was discussed and the heterogeneous electron-transfer rate constant k0 was calculated. The results show that the frequency of alternating current (ac) on the thermocouple microelectrode can be adjusted to an optimal value in order to achieve, the best heating effect Cyclic voltammetric techniques were employed to study the temperature effects on the electrochemical reaction of Fe(CN)63-/4- by global and local heating method respectively. Heterogeneous electron-transfer rate constant k0 were compared on the bulk electrode and microelectrode When the temperature was increased, the value of k0 decreased due to the generation of Prussian blue on the electrode which hindered the electrochemical reaction.3. Fabrication of a thermocouple microelectrode for application in SECM and electrochemical measurement at variable temperaturesIt is necessary to accurately control the temperature in the SECM measurement in order to achieve reliability and repeatability. Ceremic heating apparatus was set up in order to study the effect of temperature on the SECM imaging. A novel strategy for the fabrication of a thermocouple microelectrode by melting Pt and Pt-Rh wires into a measuring junction by hydroxygen flame. The thermocouple microelectrode can be employed to study the electrocatalytic oxidation of methanol. Most importantly, the thermocouple microelectrode was employed as a SECM tip in the measurement of the reactivity of Cu patterns on circuit board with bromine at variable temperatures.Since Br2 generated by the SECM tip can react with Cu substrate and produce Br-, a remarkable positive current feedback can be obtained, when the cells was heated up above 55℃, SECM images show the tip currents corresponding to the Cu substratet significantly increased 10 times as much as that of 25℃4. The construction of High frequency alternating current heating system combined with Confocal Raman spectroscopy technologyWhen magnetic field excited and local surface palsmon enhancement (LSPR) of the substrate are overlapped, the local heating effect of nanoparticles may significantly induce surface reaction process or change the surface. To study the mechanism by the thermal effect or by light, the theoretical research is especially important. High frequency alternating heating system was constructed to be Combined with Confocal Raman spectroscopy. The thermocouple microelectrode were covered with single layer of Au nanoparticles and PATP were used to modify Au NPs as SERS probe molecule. When microelectrode temperature was changed from room temperature to 160℃ with the interval of 10℃. The Raman spectra showed that ag vibration mode of DMAB and al vibration mode of PATP molecule does not significantly depended on the temperature changes.