Highly proton conductive and stable sulfonated poly(arylene-alkane) for fuel cells with performance over 2.46 W cm−2

Abstract

Polyaromatic proton exchange membranes (PEMs) are considered an ideal alternative to perfluorosulfonic acid (PFSA) membranes because of their low-cost and intrinsic low permeability. However, a PEM fuel cell's performance and stability with aromatic PEMs are lower than those with PFSA membranes due to the insufficient proton conductivity and chemical degradation. Herein, we highlight the synthesis of sulfonated poly(arylene-alkane) (Poly(FLx-BPy)-SO₃H) PEMs with a comb-like structure design of the combination of rigid ether-free backbones and locally double sulfohexyl flexible side-chains, which would enable high proton conductivity and good chemical stability. Such a comb-like structure leads to the well-developed microphase separation morphology and dense ion clusters or continuous ion channels within the membranes, thus ensuring the highest proton conductivity of 0.115 S cm⁻¹ at 25 °C and favorable anti-oxidative stability. Importantly, a H₂/O₂ PEM fuel cell (PEMFC) using an identical Poly(FL50-BP50)-SO₃H membrane and ionomer presents an outstanding power density over 2.46 W cm⁻² under 2 bar backpressure at 80 °C, which is one of the best-reported results. In the meantime, the PEMFC with this membrane exhibits an excellent stability owing to the ether-free structure and high interfacial compatibility. The comb-like design, ether-free structure and identical membrane and ionomer provide insight into the development of advanced polyaromatic PEMs.