Transport properties of SPEEK nanocomposite proton conducting membranes: optimization of additives content by response surface methodology

The addition of Cloisite 15A® Clay (CC) and 2,4,6-triaminopyrimidine (TAP) to enhance the transport properties of sulfonated poly ether ether ketone (SPEEK) nanocomposite membrane, which is a promising candidate for direct methanol fuel cell (DMFC) application, was investigated. The central composite design (CCD) of the response surface method (RSM) was utilized to optimize the content of incorporated additives in SPEEK nanocomposite membrane and predict its performance. Three models correlating the independent parameters (contents of added CC and TAP) and the responses (proton conductivity, methanol permeability and selectivity) were developed and verified with experimental data. The optimum parameters for achieving highest performance represented by methanol permeability of 2.56×10-6(cm/s), proton conductivity of 17.12(mS/cm2) and membrane selectivity of 55773.7sS/cm3 were obtained at contents of CC and TAP of 2.92 and 5.68wt%, respectively. The deviation of the corresponding experimental data was found to be in an acceptable range, confirming the suitability of RSM for predicting the membrane performance and optimizing the additives contents. The membrane with optimum additives content showed an improved structure as revealed by the field emission scanning electron microscopy (FESEM)