Influence of incorporation of Zeolitic Imidazolate Framework-67 on the performance and stability of sulfonated Polyvinylidene fluoride proton exchange membrane for fuel cell applications

In pursuit of enhanced methanol tolerance and thermal stability, a cost-effective solution was developed by integrating varied proportions of zeolitic imidazolate framework-67 (ZIF-67), a metal-organic framework, into a sulfonated polyvinylidene fluoride (SPVDF) matrix-based proton exchange membrane (PEM). Through comprehensive characterization, the uniform dispersion and chemical functionalities of SPVDF and ZIF-67 was confirmed by Scanning electron microscopy(SEM), Fourier transform infrared spectroscopy (FT-IR) respectively. This uniform dispersion is attributed by the electrostatic interaction between the –NH₂ group of Himm unit and -SO₃H group of SPVDF create a strong hydrogen bonding network (i.e. acid-base pair) resulted in improved membrane surface hydrophilicity, water uptake, proton conductivity. Further the incorporation of ZIF-67 led to a composite membrane with significantly lower methanol permeability (1.5 × 10⁻⁷ cm² s⁻¹) compared to Nafion 117 (20 × 10⁻⁷ cm² s⁻¹). For glass transition and crystallization behavior of SPVDF-1 showed good miscibility enhance the membrane thermal and mechanical stability. This reduction is attributed to the presence of a large active surface area with small pores acting as a barrier against methanol permeation. Furthermore, single-cell tests in a direct methanol fuel cell (DMFC) demonstrated that the SPVDF-1 membrane achieves a maximum power density of 82.4 mW cm⁻², surpassing that of Nafion 117 (75.9 mW cm⁻²). These results underscore the potential of the developed SPVDF-1 membrane as a promising alternative for DMFC applications.