Novel triazole functional sol–gel derived inorganic–organic hybrid networks as anhydrous proton conducting membranes

Abstract

In this work, novel inorganic–organic hybrid networks were prepared to obtain anhydrous proton conducting membranes for fuel cells. 3-glycidoxypropyl trimethoxy silane (GPTMS) was functionalized with 1H-1,2,4-triazole (Tri) and 3-aminotriazole (ATri) via ring opening of the epoxide ring and then sol–gel polymerization was performed to produce triazole containing silane networks abbreviated as Si–Tri and Si–ATri. In addition during sol–gel process trifluoromethane sulfonic acid (TA) was introduced into the matrix with several stoichometric ratios. Fourier transform infrared spectroscopy (FT-IR) confirmed the tethering of the Tri and ATri into the silane compound and the sol–gel reaction. Thermogravimetry analysis (TGA) showed that the membranes are thermally stable up to 200 °C. Differential scanning calorimeter (DSC) verified the softening effect of the dopant. The morphology of the membranes was analyzed with SEM images. The proton conductivity of these novel silane networks were studied by dielectric-impedance spectroscopy. Although proton conductivity of these membrane electrolytes depends on the acid ratio, the membrane without dopant produced a proton conductivity of 8.7 × 10−5 S/cm at 150 °C in dry state. The conductivity isotherms show Vogel–Tamman–Fulcher (VTF) behavior which implies the coupling of the charge carriers with the segmental motion of the polymer chains. A maximum proton conductivity of 8.9 × 10−4 S/cm was obtained for the sample Si–TriTA1 in the anhydrous condition.