Proton Conductivity Studies on Covalent Organic Frameworks (COFs) for The Application of High-Temperature Fuel Cells

Abstract

The polymer electrolyte membrane fuel cell (PEMFC) attracted considerable interest as a viable replacement for fossil fuels owing to its low pollutant emissions, high power density, mobility, and long operation time. The most common PEMFC membranes are made of a perfluorinated sulfonic acid membrane (Nafion). This membrane exhibits excellent proton conductivity Under fully humid conditions and low temperatures (around 80°C). Thus, operating at higher temperatures is not recommended because it leads to membrane dehydration and drastically reduces its proton conductivity. This has negative effects on PEMFC systems and causes power deterioration. Therefore, several efforts have attempted to modify existing membranes by incorporating additives in various polymer matrices to develop Nafion-free membranes for PEMFCs. Covalent organic frameworks (COFs) can be promising materials for fuel cells applications. They have the potential as proton carriers due to their enormous surface area, easy-to-tune pore size, and their high thermal stability. This work aims to develop a Nafion-free membrane based on COFs supported on porous polytetrafluoroethylene (PTFE) and zirconium phosphate as an alternative to Nafion. The preliminary results showed a high anhydrous proton conductivity in the range of 10-4 S/cm up to 150°C.