Hydrogen (H2) is a clean energy source and its inexpensive separation is important for future H.2 Energy use. Currently H.2 is made primarily from high temperature methane steam reforming reactions, and therefore the availability of membrane separation technology that can operate at elevated temperatures can reduce production costs. In this work a composite membrane made of cross-linked polybenzimidazole (PBI) triglycidyl isocyanurate (TGIC) and sulfonated graphene (SG) with a mixed proton-electron guiding concept was developed. In such a membrane, protons diffuse by hopping along the cross-links between the sulfone groups of SG and the pyrrole rings of PBI while electrons are transported above highly electronically conductive SG. After the addition of SG, the membrane became more compact due to the reduced interlayer spacing and swelling ratio. The thermal stability and oxidation resistance are comparable to those of other PBI-based membranes. For H2/ CO2 Separation, H2 a 132 μm thick membrane can be used with 99.99% selectivity and a high flow rate of up to 0.22 mL min. penetrate-1 cm-2 at 300 ° C. The stable operation at 280 ° C for 160 hours proves the robustness of the membrane at such an elevated temperature. Compared to the previously reported mixed conductive ceramic membranes with equivalent H2 The polymer and graphene composite membrane presented here can reduce the operating temperature by 500 ° C for fluxes that require operating temperatures above 800 ° C. This is an important prerequisite for a more practical integration of membrane technology into industrial processes.