Durability improvement of proton exchange membrane fuel cells by doping silica‒ferrocyanide antioxidant

Proton exchange membranes (PEMs) with remarkable chemical stability are desirable to realize long lifetimes of proton exchange membrane fuel cells (PEMFCs). In our recent work, PEMs containing radical scavenger ferrocyanide (Fc (II))/ferricyanide (Fc (III)) species were demonstrated to possess outstanding chemical stability. However, a challenge in balancing general applicability and retention remains, due to their water solubility. Here, Fc (II) is tethered to a SiO2 support to produce low water soluble SiO2-Fc (II), which could be used as a universal additive in various matrices to mitigate leaching. The composite PEMs, sulfonated polysulfone (SPSf) doped with SiO2-Fc, show much higher oxidative stability, confirmed by Fenton's test, ion exchange capacity retention and proton conductivity retention. The composite PEM also displays obviously improved durability during PEMFC operation, where the antioxidative efficacy of SiO2-Fc is evidently stronger than comparative stand-alone water-soluble species. Moreover, a PEMFC based on SPSf composite PEM shows much higher power output than that based on unfilled SPSf membrane under low humidity conditions, owing to the hydrophilicity and proton conductivity of SiO2-Fc. The present work outlines a prospective route to better utilize Fc (II)/Fc (III) antioxidant with clear benefits in general applicability and good stability, leading to progress in utilization.