Enhanced proton conductivity of the proton exchange membranes by the phosphorylated silica submicrospheres

► Phosphorylated silica with different chain lengths and -PO3H2 amounts were prepared. ► SPEEK membranes doped with phosphorylated silica were fabricated. ► Proton conductivity was dependent on the -PO3H2 amounts and grafted chain lengths. ► The highest conductivity was 0.335 S cm−1 at 60 °C (100 RH). ► The proton conduction was tentatively explained by effective acidic group amounts.