Structural modification of chitosan biopolymer as a novel polyelectrolyte membrane for green power generation

Abstract

Abstract In the present study, a series of bioresource polyelectrolytes based on chitosan were synthesized and assessed for applicability in direct methanol fuel cells (DMFCs). A binary cross‐linking agent (sulfosuccinic acid/glutaraldehyde) was used for the structural modification of chitosan and membranes comprising various amounts of sulfosuccinic acid (0, 8, 12, and 16 wt% SSA/wt chitosan) were prepared. It was found that by increasing the sulfonate groups' content up to 16 wt%, proton conductivity and methanol permeability properties reach the values of 0.0452 S cm −1 and 9.6 × 10 −7 cm 2 sec −1 , respectively. Based on the membrane selectivity evaluation and activation energy measurements of proton conduction, the optimum composition of cross‐linking agent was determined. The optimum composition resulted in a relatively high proton conductivity of 0.0452 S cm −1 and a low methanol permeability of 9.6 × 10 −7 cm 2 sec −1 . Moreover, the optimum proton exchange membrane exhibited selectivity value of 47,100 in comparison with the corresponding value of 40,500 for Nafion® 117. The fabricated membranes showed acceptable oxidative and hydrolytic stability. Furthermore, single cell DMFC performance test revealed a power density of 17 mW cm −2 at 30°C and 41 mW cm −2 at 60°C in a 2 M methanol feed. Hence, prepared proton‐conducting bioresource ionomers could have promising potential in the field of green power generation as a low cost and biodegradable polyelectrolyte. Copyright © 2009 John Wiley & Sons, Ltd.