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Self‐healing proton‐exchange membranes (PEMs) made of poly(vinyl alcohol) (PVA) and Nafion were synthesized using the freeze‐thaw method. Since PVA is more selective towards water than methanol, the blend membrane successfully reduced methanol permeability and improved selectivity compared to the recast Nafion membrane. The addition of PVA also helped the membrane self‐heal by promoting the formation of hydrogen bonds. In contrast to the pristine Nafion, which exhibited even more severe methanol crossover after being damaged than before, the Nafion‐PVA membrane underwent a self‐healing process and regained much of its methanol barrier function. These advantageous characteristics of the Nafion‐PVA membrane suggest its potential use in direct methanol fuel cells (DMFCs). [ABSTRACT FROM AUTHOR]

Getting the direct methanol fuel cell (DMFC) closer to mass production requires the creation of a high-performance and long-lasting proton exchange membrane (PEM). In this study, self-healable PEMs, Nafion-poly(vinyl alcohol)/phosphotungstic acid (N-PVA/HPW), were prepared through a simple freezing–thawing method. HPW acted as proton conductors, while PVA with reversible hydrogen bonds contributed to the self-repair ability of the membrane. The proton conductivity of the N-PVA/HPW membranes was found to be comparable to that of the pristine Nafion membrane owing to the additional proton-conducting sites and improved water retention provided by the HPW. Along with this, the packed structure of the mixed-matrix membranes led to a lower methanol permeability in all the N-PVA/HPW membranes compared to recast Nafion. As a result, N-PVA/HPW20 membrane with acceptable proton conductivity (0.062 S cm−1) and reduced methanol permeability (2.75 × 10−6 cm2 s−1) achieved the highest selectivity, where selectivity is a well-known indicator of a membrane's suitability for use in DMFC. The N-PVA/HPW20 membrane successfully recorded a peak power density of 2.7 mW cm−2, which is 10.7% higher than the value of recast Nafion. Another highlight of these mixed-matrix membranes is their ability to recover up to 93% of their initial methanol barrier properties after being damaged. This fascinating self-healing property of the membrane is believed to have the potential to extend the service life of DMFC. [ABSTRACT FROM AUTHOR]