Densely sulfonated block copolymer composite membranes containing phosphotungstic acid for fuel cellmembranes

► Studies reveal that block copolymers can offer reliable solid electrolyte membrane. ► Newly designed block copolymers were synthesized and thoroughly analyzed. ► The fabricated composite membranes were thermally more stable than Nafion-117. ► The proton conductivity of 96 mS cm−1 has been achieved from Block-19/PWA-30. ► The power density of 150 mW cm−2 was obtained from the composite membrane.