Effect of Temperature on Electrochemical Degradation of

Polyaniline (PANI) as active material of batteries possesses excellent electrochemical reversibility. It is a promising candidate for a rechargeable battery with a high performance. The polyaniline (PANI) was deposited onto the platinum electrode by cyclic voltammetry. The electrochemical degradation of PANI was studied in 1.0 M sulfuric acid aqueous solution at different temperatures. The higher temperatures lead to the irreversible change of some redox characteristic peaks. The experimental results indicate that the electrochemical degradation of PANI is first-order reaction in 1.0 M sulfuric acid solution. The degradation rate of PANI is greatly affected by temperature, which increases by approximately 4.6 times at 45°C than that of at 15 °C. The first-order degradation rate constants (k) and half-period (τ1/2) were calculated based on the change of the relative peak current over the course of the study. The morphology, structure and electrochemical properties of the PANI are also greatly affected by the temperature. Higher temperatures ( ≥ 35 oC) promote the overoxidation of the PANI, which results in decreasing the electrochemical activity of the PANI in sulfuric acid solution and the reversibility of PANI during the charge and discharge cycles, and damaging the conjugated structure of PANI. The overoxidized PANI film has a higher Rct (charge transfer resistance). Higher temperatures also destroy the porous structure of PANI. It is suggested that the optimum electrochemically operating temperature of PANI should be below 35 o C in the aqueous sulfuric acid solution