Integration of thermocouple microelectrode in the scanning electrochemical microscope at variable temperatures: simultaneous temperature and electrochemical imaging and its kinetic studies

Abstract

We describe herein a method for the simultaneous measurement of temperature and electrochemical signal with a new type of thermocouple microelectrode. The thermocouple microelectrode can be used not only as a thermometer but also as a scanning electrochemical microscope (SECM) tip in the reaction between tip-generated bromine and a heated Cu sample. The influence of temperature on the SECM imaging process and the related kinetic parameters have been studied, such as kinetic constant and activation energy.

Hot-Tip Scanning Electrochemical Microscopy: Theory and Experiments Under Positive and Negative Feedback Conditions

“…Pan et al used a thermocouple microelectrode as the tip for the SECM. 22 The heating in their setup was caused by the dc power applied to an enameled copper wire that was wrapped around a copper substrate. As a result, the temperature gradient was established in the solution.…”

“…Indirect determination involves recording of the shift in the half-wave potential determined from the cyclic voltammetry experiments; the value of the electrode temperature is then calculated using the temperature coefficient of the electrode reaction standard potential . The temperature can also be determined directly using thermocouple electrodes , and calculated based on the theoretical considerations. , …”

“…In recent years, SECM measurements at elevated temperatures have attracted considerable attention. ,, Schäfer et al described a setup which used a Peltier element as the heating device for the whole solution in the SECM cell. However, the heating pulses applied to the Peltier element led to a low signal-to-noise ratio if they were not synchronized with the current acquisition .…”

“…In addition, heating of the whole cell induced evaporation of water at high temperatures, which could lead to the uncertainty in the solute concentrations. Pan et al used a thermocouple microelectrode as the tip for the SECM . The heating in their setup was caused by the dc power applied to an enameled copper wire that was wrapped around a copper substrate.…”

“…Thus, the technique was applied to the negative feedback mode and the experimental results were compared to the simulations using COMSOL . With respect to the other approaches, , HT-SECM generates heat in a small region of the solution that is near the tip surface, without any effect on the bulk. Based on the COMSOL model developed in our previous paper, we achieved a good understanding of the temperature distribution and the electrothermal force in the solution .…”