Di-piperidinium-crosslinked poly(fluorenyl-co-terphenyl piperidinium)s for high-performance alkaline exchange membrane fuel cells

Abstract

Modern anion exchange membrane (AEM) fuel cells (AEMFCs) call for highly conductive, durable, and mechanically tough AEMs and ionomers. Here, we report a series of scalable di-piperidinium-crosslinked poly(fluorenyl-co-terphenyl piperidinium) (x-PFTP-DP-Cn) copolymers with high ion exchange capacity (IEC) and tunable crosslinking alkyl spacers (Cn, n = 5 or 10) to reinforce the mechanical strength and optimize the electrochemical performance of poly(aryl piperidinium)-based AEMFCs. Specifically, durable x-PFTP-DP AEMs display high ion conductivity (HCO₃⁻ >90 mS cm⁻¹ and OH⁻ >180 mS cm⁻¹ at 90 °C) and excellent mechanical strength (tensile strength ∼90 MPa, elongation at break ∼35%). Importantly, the x-PFTP-DP-based AEMFCs achieve outstanding peak power densities of 2.50 W cm⁻² in H₂–O₂ and ∼1.41 W cm⁻² in H₂–air at 80 °C. Moreover, the present AEMFCs can run stably under 0.2 A cm⁻² and 0.6 A cm⁻² current densities at 70 °C for 265 h and 110 h, respectively, with low voltage decay rate of ∼50 μV h⁻¹.