Sulfonated Chitosan and HKUST-1 metal organic frameworks based hybrid membranes for direct methanol fuel cell applications

Sulfonated Chitosan and copper-based metal-organic frameworks (Hong Kong University of Science and Technology (HKUST-1) or Cu-BTC or MOF-199) based hybrid membranes are fabricated using a solution casting method for direct methanol fuel cell (DMFC) applications. The well-defined cubic structure and sharp crystalline X-ray diffraction pattern confirms the successful synthesis of HKUST-1. The SEM cross-sectional images showed that incorporated HKUST-1 acts as a pore-filling agent as well as creating finger-like hydrophilic channels into the S-Chitosan matrix. The existence of intermolecular hydrogen bonding between the -COOH groups of HKUST-1 and SO3H groups of S-Chitosan enhances the membrane performances such as water uptake, ion exchange capacity, proton conductivity, and thermal stability. Specifically hybrid membrane with 0.5 wt% of HKUST-1 showed the highest proton conductivity of 5.38 x 10(-3) and 6.19 x 10(-3) S cm(-1) at 25 and 80 degrees C respectively. Besides the S-Chitosan-0.5 membrane exhibited lower methanol permeability and selectivity than pristine S-Chitosan and commercial Nafion membranes due to the small ionic size. Besides the pore reduction ability of HKUST-1 selectively allowed protons and block the methanol permeation in the membrane matrix. Overall results indicate that the S-Chitosan-0.5 hybrid membrane is a suitable candidate for DMFC applications.

Automated summary

In this study, hybrid membranes based on sulfonated chitosan and copper-based metal-organic frameworks were fabricated and investigated for direct methanol fuel cell applications. The results showed that the incorporation of copper-based metal-organic frameworks improved the membrane performances, resulting in lower methanol permeability and higher proton conductivity.