H3PO4-doped 1,2,4-triazole-polysiloxane proton conducting membrane prepared by sol–gel method

The development of anhydrous proton exchange membrane is critical for the polymer electrolyte membrane fuel cell (PEMFC) operating at intermediate temperature (100–200   °C). In the present work, H 3 PO 4 -doped 1,2,4-triazole-polysiloxane proton conducting membrane is successfully prepared by sol–gel reaction. The molecular structure of the PGA-xH 3 PO 4 is confirmed via Fourier-transform infrared spectroscopy (FTIR). Thermogravimetry (TG) analysis shows that the samples were thermally stable up to approximately 250   °C. The fracture surface morphology of the materials is characterized by scanning electron microscopy (SEM). The temperature dependence of proton conductivity of all the membranes exhibits an Arrhenius behavior. The proton conductivities of these membranes increase with dopant concentration and the temperature. In an anhydrous state, the proton conductivity of PGA-1H 3 PO 4 , PGA-2H 3 PO 4 and PGA-3H 3 PO 4 is 1.48   ×   10 −   3 , 1.07   ×   10 −   2 ,1.43   ×   10 −   2 S cm −   1 at 200   °C, respectively. According to FTIR results, the added H 3 PO 4 is presumed to break up the hydrogen-bonding network of pure PGA, facilitating ring-reorientation and thus Grotthus mechanism proton transport. In PGA-2H 3 PO 4 , the extra H 3 PO 4 may act as a bridge providing effective proton conduction. Therefore the proton conductivity of PGA-2H 3 PO 4 is greatly improved compared with PGA-1H 3 PO 4 .