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 0.6V. 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 similar to 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. Published by Elsevier Ltd.