Incorporation of polydopamine functionalized as double‐sided adhesive to connect phosphotungstic acid in Friedel‐Crafts cross‐linked SPEEK sulfonated poly(ether eether ketone) as proton exchange membranes

Abstract

Using highly sulfonated poly(ether ether ketone) (SPEEK) as the base material, the structure and properties of poly(ether ether ketone) (PEEK) membranes are optimized by precisely controlling the doping of phosphotungstic acid (HPW), dopamine (DA), and various amounts of carbon nanomaterials. Compared with conventional PEEK membranes, this optimized membrane exhibits higher proton conductivity, lower water absorption swelling rate, and excellent thermal stability. Highly SPEEK is soluble in water, thus fails to be used in fuel cell applications. Herein, we conduct Friedel‐Crafts method to obtain cross‐linked highly sulfonated membrane with controlled water uptake and swelling while still maintaining high proton conductivity. The polymer is then doped with phosphotungstic acid (HPW) to acquire enhanced performance. To control HPW leakage, polydopamine (PDA) acting as double‐sided adhesive is incorporated within the membrane. By distributing 1 wt.% PDA, the HPW leakage is reduced almost three times. The composite C‐SPEEK/HPWx/PDAy membranes have exhibited excellent overall performance. Specifically, the best proton conductivity result of C‐SPEEK/HPW50 has reached 0.271 S/cm. Moreover, it has presented superb performance in H2/O2 single cell test recorded as power density of 886.13 mW/cm2 while current density is 1614.20 mA/cm2 at 60°C.