Insights on the SO2 poisoning of Pt3Co/VC and Pt/VC fuel cell catalysts

SO2 poisoning of carbon-supported Pt3Co (Pt3Co/VC) catalyst is performed at the cathode of proton exchange membrane fuel cells (PEMFCs) in order to link previously reported results at the electrode/solution interface to the FC environment.First, the surface area of Pt3Co/VC catalyst is rigorously characterized by hydrogen adsorption, CO stripping voltammetry and underpotential deposition (upd) of copper adatoms. Then the performance of PEMFC cathodes employing 30 wt.% Pt3Co/VC and 50 wt.% Pt/VC catalysts is compared after exposure to 1 ppm SO2 in air for 3 h at constant cell voltage of 0.6 V. In agreement with results reported for the electrode/solution interface, the Pt3Co/VC is more susceptive to SO2 poisoning than Pt/VC at a given platinum loading.Both catalysts can be recovered from adsorbed sulfur species by running successive polarization curves in air or cyclic voltammetry (CV) in inert atmosphere. However, the activity of Pt3Co/VC having ∼3 times higher sulfur coverage is recovered more easily than Pt/VC. To understand the difference between the two catalysts in terms of activity recovery, platinum–sulfur interaction is probed by thermal programmed desorption at the catalyst/inert gas interface and CV at the electrode/solution interface and in the FC environment.