TiSi2O_x Coated N-Doped Carbon Nanotubes as Pt Catalyst Support for the Oxygen Reduction Reaction in PEMFCs

摘要

Composite nanostrucutres of TiSi2O_x coated nitrogen-doped carbon nanotubes (NCNTs) were synthesized by a combination of chemical vapor deposition (CVD) and magnetron sputtering processes. The synthesized nanostructures were used as supports for Pt catalyst for oxygen reduction reaction (ORR) in proton exchange memberane fuel cells (PEMFCs). An amorphous layer of TiSi2O_x with controlled thicknesses was sputtered on NCNTs and followed by post-treatment at high temperature (1000 °C, An-TiSi2O_x-NCNTs), inducing TiO2 nanoparticles of around 5 nra in diameter embedded in the amorphous layer. Further analyses via X-ray absorption spectroscopy of the Ti K edge and Si K edge revealed the Ti atoms were in a TiO2 rutile environment and the Si atoms were in a SiO2 environment. Pt nanoparticles with an average diameter of 3 nm were deposited on the composite support, and their electrochemical behaviors toward ORR were studied. It was revealed that, even with lower electrochemical surface area (ECSA), Pt/An-TiSi2O_x-NCNTs showed better catalytic activity toward ORR than Pt/NCNT catalysts. The origin of enhanced activity of PtMn-TiSi2O_x-NCNTs was examined by high resolution transmission electron microscopy (HRTEM) and the X-ray absorption near edge structure spectra (XANES) of the deposited Pt nanoparticles.