Stability study of ultra-low Pt thin film on TiO2–C core–shell structure and TiO2 encapsulated in carbon nanospheres as cathode catalyst in PEMFC

Abstract

As catalyst supports play an important role in the performance, cost, and the stability of fuel cells, we focus on synthesis of novel nanocomposites via different designs to overcome durability and cost of electrocatalyst layer. In this paper, the researchers wished to report a simple and cost effective hydrothermal method for synthesizing titania encapsulated carbon, and carbon–titania core–shell structure. This comparison was conducted in an effort to find better structure of metal oxide–carbon, as a promising replacement for carbon in PEMFC catalyst supports. Different chemical reagents were applied in order to increase the surface area, and control the porosity of supports. All produced supports at each step were extensively analyzed and discussed. Carbon structure and morphology of nanospheres were studied through Raman characterization and scanning electron microscopy. Titania structure studied through X-ray diffraction indicated two phases including the main anatase phase and the minor rutile phase. Low amounts of platinum (0.05mg/cm2) were deposited on prepared supports via constant condition in comparison to the 0.2–0.3mg/cm2 platinum for standard membrane electrode assembly. The performances of PEMFC, consisting different prepared support-platinum as cathode, were compared depending on the measured polarization curves. TiO2–Pt showed the lowest power density around 167mW/cm2 while the maximum power densities belonged to core–shell structure with 10wt% titania around 410mW/cm2 which was comparable with Vulcan–Pt. Notably, titania encapsulated carbon with the same amount of titania gave the same performance as core–shell structure. However, the accelerated potential cycling test indicated that the carbon–titania core shell structure showed higher stability in comparison to titania encapsulated in carbon. This result was discussed through X-ray photoelectron spectroscopy.