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

Abstract

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 °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 °C, these obtained composite membranes show comparable performances to a pure PFSA commercial membrane. At 120 °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 °C/90% RH, which increases with the ionomer content.

Functional Composite Separators with Cation-Trapping Abilities

“…Interestingly, the smooth and homogeneous morphology of the fibers confirms that silica in HES does not form discrete particles onto the fibers but rather forms fractal domains within them. 37,38 This feature comes from the in situ generation of silica under acidic sol−gel conditions. A major advantage is that the silica can be incorporated in large amounts while being intimately mixed with the polymer at the nanoscale, which may prevent the leaching of silica particles in the electrolyte without the need for any binder.…”