Porous polybenzimidazole (PBI) based blend membranes were prepared by adding different amounts of lignosulfonate (LS) in the presence of LiCI salt. The morphology characteristics of the PBI/LS blends were investigated by FT-IR, atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses. The relation between the membrane morphology and membrane proton conductivity was studied. Results showed that LS content has a significant influence on the membrane morphology. High amount of LS in the blend created micro -pores within the membrane where increase in the LS content up to 20 wt% resulted in membranes containing pores with a mean diameter of about 0.8 mu m. The resulting PBI/LS (0-20 wt%) membranes indicated high PA doping levels, ranging from 3 to 16 mol of PA per mole of PBI repeat units, which contributed to their unprecedented high proton conductivities of 4-96 mS cm(-1), respectively, at 25 degrees C. The effect of temperature on the proton conductivity of blends was also investigated. The results showed that by rising the temperature, the proton conductivity increases in PBI/LS blends. In the blend membrane containing 20 wt% LS, proton conductivity increased from 98 mS cm(-1) at 25 degrees C to Fuel cell 187 mS.cm(-1) 160 degrees C which can be considered as an excellent candidate for use in both high and low temperature proton exchange membrane fuel cells. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.