Achieving high cell performance based on block copolymer PBI membrane with strong acid absorbing Py-PBI segments

Abstract

Block copolymers show great promise as low-temperature proton exchange membranes (PEMs). However, their potential as high-temperature PEMs has been less explored. In this study, we synthesized a series of segmented block copolymers of polybenzimidazole (PBI), consisting of strongly acid-absorbing Py-PBI segments and fluorine-containing 6FPBI segments, which exhibited significant microphase-separated structures. To counteract the "plasticization effect" of phosphoric acid (PA) under high acid doping level (ADL), which can compromise the mechanical strength of PEMs, 3-(2,3-epoxypropyl) propyltrimethoxysilane (KH560) was introduced as a crosslinking agent to strike a balance between the ADL and the mechanical properties. The 5 % KH560–6F0.72Py0.28-PBI membrane, which features a molar ratio of 6FPBI to Py-PBI structural segments of 0.72:0.28, demonstrates the most obvious microphase separated structure, exhibiting high ADL (29.2) and proton conductivity (165.45 mS cm−1 at 180 °C). The membrane electrode assembly (MEA) employing the segmented block copolymer membrane achieved a peak power density of 936.9 mW cm−2 at 160 °C without humidification. This study highlights the significant enhancement of membrane performance achieved by constructing continuous microphase separated structures.