Temperature-Controllable Electrodes with a One-Parameter Calibration

Electrically heated electrodes have been applied for various chemical and biological sensors. However, previous electrically heated electrodes, including microwires and microdiscs, are usually small and often suffer from the requirement of frequent calibrations of the electrode surface temperature ( T_s) at different environment temperatures. Here, we fabricate a temperature-controllable disk electrode (TCDE) with a conventional size (3-5 mm in diameter). A one-parameter temperature calibration is proposed using a temperature transfer coefficient α and a structural model ( T_s = T_e + α ( T_h - T_e)) to estimate T_s ( T_h and T_e are the temperature of the heating element and environment, respectively). The value of α is unique for a TCDE and mainly dependent on the structure and materials of the electrodes and the solution in nature. Once α is experimentally determined, T_s can be calibrated and found to be applicable to wide fluctuations in room temperature (15.0-33.0 °C) with errors below 1.5% for three types of disk electrodes (gold, glassy carbon, and platinum). The required T_s can be obtained by just setting T_h without thermal characterization between the heating power and T_s. A simple relationship for exploring the dependence of α on the height ( H) and radius ( R) of the electrode materials and other constants ( a, b, c, and R₀), α = 1 - c - aH - b ( R - R₀)², is revealed by numerical simulations (COMSOL). The impact of the radii of both the insulating materials of the electrode and the electrochemical cells on T_s is also considered. The effect of the solution thermal conductivity on α is studied. TCDEs are expected to be used as a sensor platform with enhanced performance.