Cellulose-Based Proton Exchange Membrane Derived from an Agricultural Byproduct

Polymer electrolyte membrane (PEM) fuel cells, considered sustainable electrochemical devices, can convert chemical energy into electricity without carbon emission. However, there is a demand for advanced PEM technologies to enhance the devices’ performance and longevity while reducing production costs. Cellulose, the most abundant natural polymer, is emerging as a green alternative for PEM applications. In this study, cellulose is extracted from an agricultural byproduct (rice husk) to maximize sustainability and bring out the potential of using eco-friendly resources. The use of nonvolatile deep eutectic solvents for cellulose modification (sulfonation) also contributes to reducing environmental impacts. A simple casting and solvent evaporation method fabricates cellulose sulfonate-based membranes with enhanced conductivity properties. The cellulose sulfonate-based membrane proposed for fuel cells exhibits several key properties for effective operation: high proton conductivity for efficient current flow with minimal resistive losses, suitable mechanical strength and thermal stability, and reliable electrochemical stability in high-humidity, radical, and acidic environments. The membranes demonstrate high electrochemical performance with conductivity ranging from 1.79 to 2.98 mS·cm–1, indicating viability in energy-related applications. Besides, the optimized membrane shows a high elasticity modulus of 2337 MPa in a dry state, superior thermal stability up to 250 °C, and high flame resistance that can extinguish flame within 1 s after removing a flame torch, which underscores its robustness and safety in practical energy conversion technologies. The findings affirm the sustainable and promising PEM derived from cellulose, contributing not only to fuel cell applications but also to broader electrochemical and energy contexts and paving the way for more environmentally friendly energy solutions.