Characterization of Catalyst Materials for PEMFCs using Analytical Electron Microscopy

Abstract

The goal of current research is probing the relationship between catalyst features and the fuel cell performance with a range of in-depth structural analysis. The study investigated different catalyst systems including core-shell structured catalyst, catalysts with unique carbon-transition metal oxide supports. PtRu catalysts nanoparticles with unique core-shell structure, one of the most practical catalysts in PEMFC technology, have been successfully obtained with the evidence from the characterization results. It is found that the enhanced CO oxidation may be achieved through the interactions between the Pt shell and Ru core atoms, which can modify the electronic structure of the Pt surface by the presence of subsurface Ru atoms or by disrupting the Pt surface arrangement. Furthermore, the possibility of presence of the compressive strain within the Pt rich shell is proved by the lattice measurements, which could significantly affect the catalytic activity. Pt catalysts supported on complex oxide and carbon support were studied to investigate the relationship between the catalyst and its support. Observations from STEM images and HAADF and energy dispersive X-ray spectrometry demonstrate the preferential distribution of Pt nanoparticles on the hybrid supports, which include Nb2O3 / C, Ta2O5 / C, (Nb2O3+TiOx) / C, (Ta2O5+TiOx) / C, and (WO3+TiOx)/C). Such evidence indicates the interaction between the catalyst and support is based on the presence of an interconnected oxide network over the carbon support and the presence of Pt strongly connected to the oxide network. In addition, using electron energy loss spectroscopy (EELS), the electronic structure of the catalyst support under various conditions was also studied to provide further evidence of the strong metal support interaction effect.