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

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 x 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 x 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 (R) 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 degrees C and 41 mW cm(-2) at 60 degrees 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 (c) 2009 John Wiley & Sons, Ltd.