Preparation and characterization of radiation-grafted poly (tetrafluoroethylene-co-perfluoropropyl vinyl ether) membranes for alkaline anion-exchange membrane fuel cells

Novel alkaline anion-exchange membranes (AAEMs) were synthesized by graft copolymerization of vinylbenzyl chloride onto pre-irradiated poly (tetrafluoroethylene-co-perfluoropropyl vinyl ether) film, followed by quaternization and alkalization. Two kinds of radiation modes, continuous radiation and dis-continuous radiation (with 15 min break in each hour's radiation), were conducted to the PFA films. The structure of the AAEMs was characterized by Fourier transform infrared (FT-IR). The performances of the AAEMs, including ion exchange capacity (IEC), ionic conductivity, water uptake (WU) and methanol permeability, were investigated systematically. The results showed that the degree of grafting of the film prepared by continuous irradiation is higher than the one prepared by discontinuous irradiation, which results in higher IEC, WU and ionic conductivity. The continuously irradiated membrane exhibited a maximum ionic conductivity of 0.05 S cm−1 at 60 °C. A maximum power density of 16 mW cm−2 for a direct methanol single cell was obtained at 60 °C with the continuously irradiated membrane as the electrolyte, MnO2/C and PtRu/C as the cathode and anode electrocatalysts, respectively. This result indicates that the direct alcohol alkaline anion-exchange membrane fuel cell is a promising system with further improvement on AAEMs.

Research highlights▶ PFA based quaternized membranes are synthesized by radiation grafting method. ▶ The membranes are for alkaline fuel cell as solid electrolyte. ▶ Radiation mode determines the IEC and ionic conductivity of the membranes. ▶ The membrane exhibited a maximum ionic conductivity of 0.05 S cm−1 at 60 °C. ▶ A power density of 16 mW cm−2 for a direct methanol fuel cell was obtained at 60 °C.