Polyvinyl alcohol/carbon nano-tube/potassium hydroxide electrolytes for direct methanol alkaline fuel cells

This study reports the cell performance of direct methanol alkaline fuel cells (DMAFCs) employing hydroxide conducting membranes. The membrane electrode assemblies (MEA) consisted of carbon-supported platinum/ruthenium for anode, platinum for cathode, and poly(vinyl alcohol) (PVA)/carbon nano-tube (CNT)/KOH membranes as polymer electrolytes. The CNT was grafted with PVA chains and PVA/CNT composite membranes were prepared using a direct mixing process and solution casting method. The aggregated hydrophilic regimes of CNT served as hydroxide-conducting micro-channels and increased the ionic conductivity of the KOH-doped PVA/CNT films. The electrolyte with CNT exhibited higher maximum power density and could be operated at a higher current density due to the reduction in methanol crossover. The maximum power density and open-circuit voltage was monitored for DMAFCs at various operating conditions. The effects of methanol concentration, methanol/KOH ratio and operating temperature on the cell performance were determined and discussed with the electrolyte characteristics.