Synergistic Effect of Polydopamine-Modified CaZrO₃ Perovskite and Hydroxylated SPEEK on Acid–Base Cation Exchange Membrane Fuel Cells

Abstract

Polydopamine-coated calcium zirconate (DCZT) nanoparticles are synthesized and dispersed in the hydroxylated sulfonated poly(ether ether ketone) (SPEEK-OH) to prepare a nanohybrid combination (SPEEK-DCZT). SPEEK-OH is prepared via the reduction process and verified by the NMR study. The formation of DCZT through condensation reaction is confirmed by FTIR, XPS, and FE-SEM analysis. The polydopamine in DCZT provides good dispersion and creates acid−base bridges (−S− O − ••• + H−HN−) at the filler and polymer interfaces via ionic interaction, improving the compatibility of the SPEEK-OH matrixes. Moreover, the acid−acid interaction that also exists between the SPEEK-OH matrixes via sulfonic and hydroxyl groups (−S− O − ... + HO) enhances the transport (Grotthuss) and thermomechanical property. At 6 wt % DCZT, SPEEK-OH shows a superior Young's modulus (662 MPa) and transition temperature (98 °C) and also shows the highest water uptake and lowest swelling ratio (47.3 and 26.2% at 80 °C). This membrane exhibits the highest conductivity of 70.9 mS cm −1 and a power density of 155 mW cm −2 at 80 °C with 75%RH, which are higher than those of SPEEK (9.53 mS cm −1 and 59 mW cm −2 ) and Nafion 117 (63.2 mS cm −1 and 142 mW cm −2 ).