Effect of Ta–TiO2 Nanoparticles in Anion Exchange Membranes: Improved Hydroxide Ion Conductivity and Mechanical Strength for Alkaline Water Electrolysis Cells

Abstract

To improve the properties of quaternized QPAF-4 copolymers as anion exchange membranes, compositing with hydrophilic Ta–TiO₂ particles are investigated. Flexible QPAF-4/Ta–TiO₂ composite membranes are obtained using solution-casting and die coating methods. Cross-sectional scanning electron microscopy reveals that the die coating method produces a more homogenous and uniform distribution of Ta–TiO₂ particles in the composite membranes than the solution-casting method. The Ta-TiO₂ particles promotes the suppression of water absorbability and dimensional swelling of the composite membranes which is more pronounced in the die coated membranes. The Ta–TiO₂ increase hydroxide ion conductivity to 116.9 mS cm⁻¹ at 80 °C for the die-coated membrane, surpassing that of the pristine QPAF-4 membrane (92 mS cm⁻¹). Ta–TiO₂ with the composite membranes survive in 4 m KOH at 80 °C for 1000 h, maintaining 96–112 mS cm⁻¹ (88–99% remaining) of initial conductivity. All composite membranes exhibit higher mechanical robustness (elongation of >200%), with the die-coated composite membranes. The optimized die coated composite membrane is fabricated in an alkaline water electrolysis cell achieving 1.63 V at 1.0 A cm⁻² (75.5% efficiency).