| In this paper, TG-DTG technology was used to study the thermal degradation behavior of PFSA with different heating rates. The thermal degradation kinetics was investigated, and the possible thermal decomposition mechanism was deduced. In addition, the effect of Pt or Mn ion and hydrogen peroxide on the stability of the proton exchange membrane in the fuel cell were simulated:1:The thermal degradation behavior of PFSA membrane was investigated by TG-DTG and ATR-FTIR, and the activation energy of the first and second decomposition stages were calculated; In addition, the two reaction stages of thermal degradation mechanism of function were obtained. The thermal degradation mechanism in first stage is controlled by the Johnson-Mehl-Avrami equation (random nucleation and subsequent growth, An, JMA (n)) mechanism functions, where f(a) is n×(1-?)×[-ln(1-?)]1-1/n, G(?) is [-ln(1-?)]1/n (n=2.6). Thermal degradation mechanism in second stage is obeyed by the power law function (P1, accelerated ?-t curve), the mechanism of the function f(a) is n(?)(n-1)/n, G(?)=?1/n(n=0.65).2:The chemical degradation of Mn metal ions and hydrogen peroxide on the fuel cell proton exchange membrane was simulated. The effects of manganese ions, hydrogen peroxide concentration and immersion time on the stability of the films were studied by means of TG-DTG, ATR-FTIR, SEM and DMA. The surface morphology and electrical conductivity of the films were determined. The results indicated that the decomposition peak temperature of the sulfonic acid group of a treated film almost disappeared at 250-380?. An isothermal test indicated that the vibrational peaks of the membranes' IR spectra were almost unchanged before and after treatment, when heated at 200?in the air. However, when heated at 315? for 2h, the intensity of the stretching vibration peaks of CF2 at 1210cm-1 decreased by 67.7%, SEM results showed that there were many holes formed on the surface of the degradation film, but the change of the resistance and conductivity of the film before and after degradation was small; DMA analysis showed that the glass transition temperature of Tg was almost disappeared.3:Pt electrode usually used as an internal electrode catalyst for fuel cell, when the fuel cell run after a period of time, Pt metal particles begain to dissolution and deposition on the membrane surface. The effect of metal Pt ions and hydrogen peroxide exist on membrane chemical degradation was simulated. The degrade membranes were obtained by dipping in different concentration of Pt metal ions and H2O2 solution. The degradation of the membrane and the loss of F- ion were investigated by TG-DTG and ICP-OES chromatography. The results showed that Pt metal ions in hydrogen peroxide solution on membrane produced strong interactions, plasma atomic emission spectrometer experiment confirmed the corrosion film in the presence of a Pt metal ion; Anion chromatography detected the presence of F- after etching solution, indicating after membrane corroded for a period of time, the C-F bond was fractured and F- outflow. |
PDF Full Text Request