Ultra-high Prussian blue loading in SPEEK matrix fabricated by one-step electrostatic spraying as proton exchange membranes for fuel cell

Mixed matrix proton exchange membrane is promising for fuel cell application, but maximizing nanofiller loading to enhance performance is significant challenge. This study developed a one-step electrostatic spraying strategy to prepare ultra-high Prussian blue loading (up to 66.7 wt%) in sulfonated poly (ether ketone) matrix (PB@SPEEK). By coupling the electrostatic spraying and in situ solvent evaporation densification, SPEEK fills the voids between PB nanoparticles, forming a bicontinuous microstructure in the membrane. The ultra-high PB content of 66.7 wt% enable a fully utilization of its intrinsic properties, resulting in extremely low swelling ratio of 3.4 % at 80 °C, excellent flexibility of freely folding, and nearly 100 % mass retention after 12-h immersion in Fenton reagent at 60 °C. In single-cell tests, the PB@SPEEK mixed matrix membrane shows stable internal resistance due to easily water hydration, therefore achieving excellent low-temperature peak power (1973.9 mW/cm 2 at 40 °C and 2078.0 mW/cm 2 at 60 °C). The strategy developed in this study enables the one-step preparation of large-area, ultra-thin and ultra-high capacity of inorganic nanofiller mixed matrix proton exchange membranes for high-performance fuel cell.