“…Despite all these advantages, Nafion ® membranes present some limitations i.e., ionconductivity drops rapidly in anhydrous conditions (RH < 80%) restricting the temperature to that not exceeding the boiling point of water and Nafion ® is an expensive material priced at about 500–700$ per m 2 [ 6 , 7 , 8 ]. So over the last few years, many alternative polymeric materials for PEM have been proposed which include sulfonated polyether ether ketone (sPEEK) [ 9 , 10 , 11 ], sulfonated polysulfone (sPSU) [ 12 , 13 ], sulfonated polyether sulfone (sPES) [ 14 , 15 , 16 ], polybenzimidazole (PBI) [ 17 , 18 , 19 ] and sulfonated polystyrene (sPS) [ 20 , 21 , 22 ]. In addition, many research groups have prepared composite PEMs using organic and inorganic fillers like TiO 2 , ZrO 2 , ZrP, BPO 4 , graphene oxide (GO), and SiO 2 to enhance the properties of proton exchange membranes [ 23 , 24 , 25 , 26 , 27 , 28 ].…”