Degradation of perfluorinated sulfonic acid films: An in-situ infrared spectro-electrochemical study

The in-situ Fourier transform infrared (FTIR) spectro-electrochemical method was used to evaluate the degradation mechanism of perfluorinated sulfonic acid (PFSA) polymer for the first time. The effect of H2O2 concentration in Fenton's reagent on the PFSA film degradation was studied. It was found that the effect of the H2O2 concentration on the chemical degradation of the PFSA film was limited, whereas, the electrochemical degradation was obviously enhanced at higher H2O2 concentrations. The chemical degradation of PFSA film in Fenton's reagent was similar to that in pure H2O2 solution. However, the results indicated that the electrode potential is the dominating factor affecting the degradation of the PFSA film. It is clear that the electrochemical degradation of PFSA film in Fenton's reagent is more serious than that in pure H2O2 solution. Moreover, it is indicated that the main cause of the membrane degradation is the instability of the backbone of the polymer chain under electrochemical conditions and secondarily the loss of sulfuric groups in the side-chains. It is concluded that the in-situ FTIR spectro-electrochemical method could be used to evaluate more objectively the degradation of the polymer film.