“…However, usage of existing PFI membranes was limited owing to very high cost, operation temperature that is restricted to 70–80°C, and high methanol crossover 3 . In recent decades, researchers devoted their attention to the development of low‐cost, high‐performance PEMs for fuel cell applications 3–7 . Sulfonated polyethersulfone (SPES), 4,5 sulfonated poly(ether ether ketone) (SPEEK), 6–9 sulfonated polysulfone, 3,10,11 sulfonated poly(aryl ether ether ketone ketone)s, 12 sulfonated poly(ether ketone ketone), 13 and so on have been utilized for the preparation of PEMs owing to their outstanding mechanical properties, thermal stability, and conductivity and also to overcome the disadvantages of PFI membranes 6–13 …”