Platinum Supported on Functionalized Carbon Nanotubes for Oxygen Reduction Reaction in PEM/AEM Hybrid Fuel Cells

Abstract

Platinum supported on oxygen and nitrogen functionalized carbon nanotubes are evaluated and compared to the commercially available platinum catalysts (Pt/C) in hybrid PEM/AEM H2/O2 and direct methanol fuel cells (DMFCs). The functionalized carbon nanotubes are synthesized by the sonichemical method. The existence of oxygen and nitrogen functional groups on the nanotubes is confirmed by X-ray photoelectron spectroscopy (XPS). The size of the platinum structures on the functionalized carbon nanotubes is measured by transmission electron microscopy (TEM) and the crystallographic properties are evaluated by X-ray diffraction (XRD). The performance of the catalyst for the oxygen reduction reaction (ORR) in each hybrid fuel cell is found to be dependent on the type of the functional groups on the carbon nanotubes. The platinum supported on both nitrogen and oxygen functionalized carbon nanotubes(Pt/CNTON) and on oxygen functionalized carbon nanotubes (Pt/CNTOX) are more effective in hybrid H2/O2 fuel cells compared to the Pt/C. However, the Pt/CNTON is not stable in hybrid DMFCs while Pt/CNTOX exhibited the best performance. The result suggests that CNTON may facilitate undesired methanol crossover reactions.