Flexible Nanocellulose/Lignosulfonates Ion-Conducting Separators for Polymer Electrolyte Fuel Cells

• Published in: Nanomaterials (Basel, Switzerland) Vol. 10; no. 9; p. 1713
• Main Authors: Vilela, Carla, Morais, João D., Silva, Ana Cristina Q., Muñoz-Gil, Daniel, Figueiredo, Filipe M. L., Silvestre, Armando J. D., Freire, Carmen S. R.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 29.08.2020; MDPI
• Subjects: Aqueous solutions; bacterial nanocellulose; biobased separators; By products; Cellulose; Conductors; Crosslinking; Electrolytes; Electrolytic cells; Fabrication; Fourier transforms; Fuel cells; Fuel technology; Ion currents; Ion exchange; ion-exchange membranes; Lignin; Lignosulfonates; mechanical performance; Mechanical properties; Membranes; Modulus of elasticity; Morphology; Polymers; Polysaccharides; Proton exchange membrane fuel cells; Pulping; Raw materials; Relative humidity; Robustness; Scanning electron microscopy; Separators; Sulfite; Sulfonation; Sulfur content; Tannic acid; thermal-oxidative stability; Thermogravimetric analysis; United Kingdom > UK; United States > US; Japan; Germany
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano10091713

The utilization of biobased materials for the fabrication of naturally derived ion-exchange membranes is breezing a path to sustainable separators for polymer electrolyte fuel cells (PEFCs). In this investigation, bacterial nanocellulose (BNC, a bacterial polysaccharide) and lignosulfonates (LS, a by-product of the sulfite pulping process), were blended by diffusion of an aqueous solution of the lignin derivative and of the natural-based cross-linker tannic acid into the wet BNC nanofibrous three-dimensional structure, to produce fully biobased ion-exchange membranes. These freestanding separators exhibited good thermal-oxidative stability of up to about 200 °C, in both inert and oxidative atmospheres (N2 and O2, respectively), high mechanical properties with a maximum Young’s modulus of around 8.2 GPa, as well as good moisture-uptake capacity with a maximum value of ca. 78% after 48 h for the membrane with the higher LS content. Moreover, the combination of the conducting LS with the mechanically robust BNC conveyed ionic conductivity to the membranes, namely a maximum of 23 mS cm−1 at 94 °C and 98% relative humidity (RH) (in-plane configuration), that increased with increasing RH. Hence, these robust water-mediated ion conductors represent an environmentally friendly alternative to the conventional ion-exchange membranes for application in PEFCs.