Highly conductive and stable hybrid ionic cross-linked sulfonated PEEK for fuel cell

Poly(Alkyl-Terphenyl Piperidinium) Ionomers and Membranes with an Outstanding Alkaline-Membrane Fuel-Cell Performance of 2.58 W cm-2

Aryl-ether-free anion-exchange ionomers (AEIs) and membranes (AEMs) have become an important benchmark to address the insufficient durability and power-density issues associated with AEM fuel cells (AEMFCs). Here, we present aliphatic chain-containing poly(diphenyl-terphenyl piperidinium) (PDTP) copolymers to reduce the phenyl content and adsorption of AEIs and to increase the mechanical properties of AEMs. Specifically, PDTP AEMs possess excellent mechanical properties (storage modulus>1800 MPa, tensile strength>70 MPa), H2 fuel-barrier properties (<10 Barrer), good ion conductivity, and ex-situ stability. Meanwhile, PDTP AEIs with low phenyl content and high-water permeability display excellent peak power densities (PPDs). The present AEMFCs reach outstanding PPDs of 2.58 W cm-2 (>7.6 A cm-2 current density) and 1.38 W cm-2 at 80 °C in H2 /O2 and H2 /air, respectively, along with a specific power (PPD/catalyst loading) over 8 W mg-1 , which is the highest record for Pt-based AEMFCs so far.

Effect of Micromorphology on Alkaline Polymer Electrolyte Stability

Recent studies demonstrated that the chemical stability of alkaline polymer electrolytes (APEs) could be improved by reducing the inductive effect between cations and backbones. Therefore, pendent cations were recommended. However, microphase-separated morphologies would be generated by elongating the spacer between cations and backbones, which have a significant influence on the chemical stability of APEs too. In order to analyze how the patterns of micromorphology affect the chemical stability of the materials, in the present work, four APEs ( a₁-QAPS, a₃-QAPS, a₅-QAPS, and a₇-QAPS) with different lengths of side chain between polysulfone and quaternary ammonium are synthesized. The longer the side chain is, the more obvious the microphase separation for the a _x-QAPS membranes is observed. After immersing in a hot alkaline solution (80 °C, 1 M KOH) for 30 days, a₅-QAPS exhibits the highest chemical stability. The ion exchange capacity and ionic conductivity of  a₅-QAPS film are reduced by 10.0 and 10.5%, respectively. The weight loss of  a₅-QAPS membrane is 8.0%, which is similar to the value of the pristine backbone. The increased chemical stability can be ascribed to the suitable micromorphology constructed in  a₅-QAPS sample. Besides,  a₅-QAPS membrane shows a high conductivity of 75.5 mS cm^-1, whereas the swelling ratio is limited to 15.0% in liquid water at 80 °C. In addition, a peak power density of 339.1 mW cm^-2 is obtained by applying a₅-QAPS as the APE to the H₂-O₂ fuel cell at 60 °C.