Anatase titania coated CNTs and sodium lignin sulfonate doped chitosan proton exchange membrane for DMFC application

Abstract

Anatase titania coated CNTs (TCNTs) and sodium lignin sulfonate (SLS) were introduced to chitosan membrane to improve the conductivity based on extra proton transfer channels built by TCNTs and sulfonate groups supplied by SLS. Water uptake, mechanical properties, oxidation stability and methanol-rejecting property of composite membranes were characterized. The results show that TCNTs and SLS doped membranes have enhanced conductivity and the sample with 5% TCNTs and 2% SLS doped (CS/TCNT-5/SLS-2) achieved a conductivity of 0.0367 S cm−1 at room temperature and 0.0647 S cm−1 at 60 °C, which is much higher than pure chitosan membrane. Moreover, with TCNTs incorporation, the mechanical properties, oxidation stability and methanol-rejecting property also improved. Overall, selectivity of CS/TCNT-5/SLS-2 sample achieved 28.2 × 104 S s cm−3 which is much higher than 3.8 × 104 S s cm−3 of pure chitosan membrane. Thus, with enhanced properties, chitosan composite membrane could be promising as proton exchange membrane (PEM) in the use of direct methanol fuel cell (DMFC).