Advanced Functional Hybrid Proton Exchange Membranes Robust and Conductive at 120 degrees C

Proton-exchange membrane fuel cell vehicles offer a low-carbon alternative to traditional oil fuel vehicles, but their performances still need improvement to be competitive. Raising their operating temperature to 120 degrees C will enhance their efficiency but is currently unfeasible due to the poor mechanical properties at high temperatures of the state-of-the-art proton-exchange membranes consisting of perfluorosulfonic acid (PFSA) ionomers. To address this issue, xx designed composite membranes made of two networks: a mat of hybrid fibers to maintain the mechanical properties filled with a matrix of PFSA-based ionomer to ensure the proton conductivity. The hybrid fibers obtained by electrospinning are composed of intermixed domains of sulfonated silica and a fluorinated polymer. The inter-fiber porosity is then filled with a PFSA ionomer to obtain dense composite membranes with a controlled fibers-to-ionomer ratio. At 80 degrees C, these obtained composite membranes show comparable performances to a pure PFSA commercial membrane. At 120 degrees C however, the tensile strength of the PFSA membrane drastically drop down to 0.2 MPa, while it is maintained at 7.0 MPa for the composite membrane. In addition, the composite membrane shows a good conductivity of up to 0.1 S cm(-1) at 120 degrees C/90% RH, which increases with the ionomer content.