Self-healing and highly elastic fluorine-free proton exchange membranes comprised of poly(vinyl alcohol) derivative and phytic acid for durable fuel cells

Fluorine-free proton exchange membranes (PEMs) capable of healing from physical damage are important for PEM fuel cells (PEMFCs) with extended service life and enhanced reliability. Herein, highly elastic fluorine-free PEMs with excellent self-healing ability and high proton conductivity are fabricated through complexation of phytic acid (PA) with sulfonated polyvinyl alcohol (SPVA), followed by subsequent grafting of SPVA with positively charged 4-(1H-imidazol-1-yl)benzenecarbaldehyde (IBZ). Compared with recast Nafion membranes, the as-prepared SPVA-IBZ/PA membranes exhibit an enhanced mechanical strength and elasticity and can spontaneously recover from a ∼50% strain to their initial states within ∼30 s at room temperature. Meanwhile, the SPVA-IBZ/PA membranes have a proton conductivity of ∼0.095 S cm−1 at ∼70°C, which is higher than that of recast Nafion membranes. The hydrogen-powered PEMFCs using the SPVA-IBZ/PA membranes, which show an open circuit voltage of ∼0.98 V and maximum power density of ∼609 mW cm−2, exhibit a satisfactory cell performance. Importantly, the SPVA-IBZ/PA membranes can spontaneously heal mechanical damage of several tens of micrometers in size and restore their original proton conductivity and cell performance under the working conditions of PEMFCs.