Enhanced hiqh-temperature polymer electrolyte membrane for fuel cells based on 1H- 1,2,3-benzotriazole and sulfonated poly(vinyl alcohol)

摘要

Fuel cells based on polymer electrolyte membranes have been widely studied during the last four decades due to their promising high energy conversion efficiency, their high energy density power sources for both automobiles and stationary applications. The development of anhydrous proton conducting membrane is important for the operation of polymer electrolyte membrane fuel cell (PEMFC) at intermediate temperature (100-200 °C). Therefore, there has been a great deal of research in the development of anhydrous electrolyte membranes with high proton conductivities at higher temperatures [1-4]. One approach was the use of nitrogen-containing aromatic heterocycles molecules -with boiling points higher than water- as proton carriers, either as doping agents or immobilized in the polymer backbone, originating polymers with intrinsic proton conductivity. 1H-1,2,3-benzotriazole (BTri) is a novel heterocyclic molecule with melting and boiling points of 100 and 350 °C, respectively. Previously it was used as dopant in polyvinyl phosphonic acid and Nation and high proton conductivity (10~3 S/cm at 150 °C) was reported [5]. In this study, we have prepared the acid-base composite materials by mixing of a sulfonated poly(vinyl alcohol) (PVA) with the high proton exchange capacity and an organic base heterocycle, 1 H-1,2,3-benzotriazole. Sulfonic acid groups were introduced into PVA matrix at various molar ratios by modifying the chemical structure of the PVA through esterification with sulfosuccinic acid (SSA), which has sulfonic acid groups. The resulting cross linked polymer was blended with 1 H-1,2,3-benzotriazole at several molar ratios (Table 1) to obtain a matrix that has acid groups immobilized into the chain and azoles interacting with the acid groups in the matrix. The polymers were characterized with Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The proton conductivity of the anhydrous samples was studied by an impedance spectrometer, and the results are compared with the previously reported systems.