(541e) Polymer/Carbon Nano-Tube Composites for Alkaline Fuel Cell Applications

Polybenzimidazole (PBI)-functionalized multi-walled carbon nano-tubes (CNTs) are obtained via an ozone-mediation route. The PBI nano-composites containing small amounts (<1%) of CNTs are prepared using solution casting methods. These thermally stable PBI and PBI/CNT composites are doped with potassium hydroxide (KOH) solution to prepare hydroxide-conducting electrolytes for alkaline direct methanol fuel cell (ADMFC) applications. The CNTs-containing composites exhibit higher fractional free volumes and higher water diffusivities. The CNTs also promote ionic conductivity of electrolytes and improves the fuel cell performance. Gas diffusion electrodes (GDEs) without polytetrafluoroethene (PTFE) treatment give superior cell power density compared to commercial E-tek GDEs, which contain hydrophobic PTFE layers. When the fuel cell is fed with 2 M methanol in 6 M KOH (as the anode fuel) and humidified oxygen (as the cathode oxidant), the system achieves a maximum power density of 104.7 mW cm^-2 at 90°C. These KOH-doped PBI/CNT composites have the potential to be used in high temperature alkaline fuel cell applications.