Enhanced proton conductivity of viscose-based membranes via ionic modification and dyeing processes for fuel cell applications

Proton exchange membranes (PEMs), which are crucial fuel cell parts, play an important role in the field of energy science. However, the further development of conventional PEMs based on synthetic polymers is greatly limited by high energy consumption and difficult degradation. In this work, we reported the fabrication of a novel viscose-based PEM via cationic modification and dyeing treatment with the reactive dyes KE-7B1. High-efficiency proton transmission channels can be constructed due to the formation of the complex internal three-dimensional network of the as-prepared viscose-based PEM. H+ conductivity (σH+) and water uptake are intensively investigated by changing the cationic agents and KE-7B1, and the maximum σH+ reaches 44.19 mS/cm at 80 °C and 98% relative humidity (RH). Furthermore, the prepared membrane shows the lowest calculated activation energy value (12.25 kJ/mol), indicating that both Grotthuss and Vehicle mechanisms play an important role in ionic transport. The membrane chemical structure and micromorphology are analyzed and the proton transmission modes are explored in detail, supplemented with research on the hydrophilic/hydrophobic characteristics and crystallinity of the membranes. The application stability of the membranes is also evaluated analyzing the thermal, mechanical, and oxygen resistance properties, and the results show that all the prepared membranes can maintain good thermal stability within 200 °C. The maximum tensile strength reaches 42.12 MPa, and the mass losses of the membranes soaked in 30% (in mass, same below) H2O2 solution for 120 h can be restricted to 10%. Therefore, as a novel PEM, the obtained dye viscose-based membranes show great potential for application in fuel cells.