Abstract
In this work, multi-walled carbon nano-tubes (CNTs) were modified with pendant Fe 3 O 4 nanoparticles and polyvinyl alcohol (PVA) polymer chains. These functionalized CNTs (FeCNT) were incorporated into a PVA solution and used to prepare a cast film. The use of the pendant Fe 3 O 4 nanoparticles resulted in a loose crystal structure with low crystallinity for the PVA matrix. With an increased fractional free volume, the water solubilities and diffusivities were enhanced in the FeCNT-containing composite membranes. The methanol permeability was reduced in the PVA-FeCNT sample. The PVA and PVA-FeCNT films were doped with a potassium hydroxide (KOH) solution to prepare hydroxide-conducting solid electrolytes. The ionic conductivity of the KOH-doped PVA-FeCNT composite membrane was improved by the FeCNT addition. This improvement was ascribed to the increased polymeric amorphous region with the ionic conducting micro-channels provided by the FeCNT. These electrolytes were used in direct methanol alkaline fuel cells. An open-circuit potential and a peak power density of 0.87V and 87.8mWcm -2 , respectively, were obtained using a 2M methanol fuel in 6M KOH at 60°C with the PVA-based electrolyte containing 0.15% FeCNT. This peak power density was more than double the value observed without the FeCNT incorporation. © 2013 Elsevier B.V.