| Thermoelectrochemistry is a subject that combines the theories and methods of both thermo-and electro-chemistry to investigate the reversible electrode reactions. Use of the thermo-electrochemical method to obtain the parameters of thermodynamics and kinetics of the electrochemical reaction by measuring the heat flow (temperature difference), electrode potential, current and time signals, simultaneously, can provide significant information for analysis of the consider electrode reactions.In this work, a precision electrochemistry calorimetrical system with lower temperature-fluctuate (±0.001K) was applied. The electrochemical Peltier heats (EPH) of Fe(CN)63-/Fe(CN)64-system at five different concentrations under the condition of constant cathodic currents cathode polarized by different current strength were measured. And the experiment data were analyzed and processed according to the theory of Thermoelectrochemistry and the method of data processing. The main results are as follows:(1) The Fe(CN)63-/Fe(CN)64-system was polarized by different current strength at295.15K, and the time lasted for120seconds. The curves of the electrode potentials and output electric signals of temperature changes against time at the five different concentrations under the condition of different polarization currents were obtained. The results shows that the EPH for the cathodic process of Fe(CN)63-/Fe(CN)64-couple under various concentrations at295.15K are, respectively, acquired as:-41.31,-42.73,-44.28,-45.87and-46.65kJ·mol-1at the respective concentrations of0.125,0.175,0.225,0.275and0.300mol·L-1. And the apparent enthalpy change are correspondingly determined as-89.01,-90.86,-92.91,-94.87and-95.78kJ·mol-1at the respective concentrations.Extrapolating the zero concentration, the EPH and the apparent enthalpy change values on absolute scale for the considered couple at 295.15K are-37.42kJ·mol-1and-84.10kJ·mol-1, respectively.(2) The Fe(CN)63-/Fe(CN)64-system was polarized by different current strength at303.15K, and the time lasted for120seconds. The curves of the electrode potentials and output electric signals of temperature changes against time at the five different concentrations under the condition of different polarization currents were also obtained. The results shows that the EPH for the cathodic process of Fe(CN)63-/Fe(CN)64-couple under various concentrations at303.15K are, respectively, acquired as:-35.63,-36.81,-38.17,-39.71,-40.36kJ·mol-1at the respective concentrations of0.125,0.175,0.225,0.275and0.300mol·L-1. And the apparent enthalpy change are correspondingly determined as-80.31,-82.79,-85.01,-86.81,-87.92kJ·mol-1at the respective concentrations.Extrapolating the zero concentration, the EPH and the apparent enthalpy change value on absolute scale for the studied couple at303.15K are-32.10kJ·mol-1and-75.13kJ·mol-1, respectively. |
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