Mechanical property enhancement of ultra-thin PBI membrane by electron beam irradiation for PEM fuel cell

The ultra-thin cross-linked PBI membrane containing phosphoric acid (PA) for possible use in a fuel cell was prepared by electron beam irradiation method. The preparation procedure involved two steps: (a) irradiation of PBI membranes (PBI-1, PBI-2 and PBI-3) by an electron beam with increased dose energy and (b) doping the irradiated membranes with PA. These membranes were characterized in terms of mechanical properties, chemical and thermal stability were evaluated using Universal Testing machine, Ultraviolet-visible spectroscopy and thermogravimetric analysis, respectively. Compared to the pristine PBI membrane of thickness 20 μm, the cross-linked PBI membranes show much better mechanical properties and improved chemical and thermal stability. In addition, the tensile strength of the cross-linked PBI membranes with PA ranges from 19 MPa to 27 MPa, which is higher than that of the pristine PBI membrane with PA (14 MPa). Besides these, the fuel cell performance of the PBI-1 is similar to that of the pristine PBI membrane of thickness 20 μm, but higher than common used PBI membrane of thickness 40 μm. The overall results suggest that the membrane has a great potential for possible application in high temperature PEM fuel cell.