Cellulose Nanocrystals-Based Membrane: Enhancing Dimensional Stability and Water Uptake for Alkaline Fuel Cells

The design of anion-conducting polymeric materials has been an active field of research, driven by their application in alkaline fuel cells. These membranes offer advantages such as higher cell efficiencies and cost-effectiveness. However, a major challenge lies in balancing high conductivity with excessive water uptake, which can lead to uncontrolled dimensional swelling or membrane disintegration. In this study, we present a unique approach to address this challenge by utilizing cellulose nanocrystals as the basis for a membrane design. Cellulose nanocrystals, derived from cellulose-rich sources through acid or base hydrolysis, possess exceptional mechanical properties and are known for their high water absorption capabilities while maintaining excellent dimensional stability. By incorporating cellulose nanocrystals with various commercially available polymeric binder systems, we prepared an electrolyte membrane for alkaline fuel cells. We systematically investigated the impact of cellulose nanocrystal content, binder formulations, and temperature on water absorption, swelling, and hydroxide conductivity. Our results demonstrate that the resulting membrane exhibits improved dimensional stability, with less than 10% swelling, and excellent water uptake exceeding 100% compared to membranes solely based on polymer binders. Importantly, the presence of cellulose nanocrystals does not compromise the hydroxide conductivity of the polymer binder system. This approach offers a facile and renewable strategy for preparing solid electrolytes with exceptional dimensional stability and high hydroxide conductivity. It represents a promising avenue for the development of solid electrolytes in alkaline fuel cells, offering a simpler alternative to complex polymer synthesis routes.