Understanding the Bifunctional Effect for Removal of CO Poisoning: Blend of a Platinum Nanocatalyst and Hydrous Ruthenium Oxide as a Model System

CO poisoning of Pt catalysts is one of the most critical problems that deteriorate the electrocatalytic oxidation and reduction reactions taking place in fuel cells. In general, enhancing CO oxidation properties of catalysts by tailoring the electronic structure of Pt (electronic effect) or increasing the amount of supplied oxygen species (bifunctional effect), which is the typical reactant for CO oxidation, has been performed to remove CO from the Pt surface. However, though there have been a few reports about the understanding of the electronic effect for rapid CO oxidation, a separate understanding of bifunctional modification is yet to be achieved. Herein, we report experimental investigations of CO oxidation in the absence of electronic effect and an extended concept of the bifunctional effect. A model system was prepared by blending conventional Pt/C catalysts with hydrous ruthenium oxide partides, and the CO oxidation behaviors were investigated by various electrochemical measurements, including CO stripping and bulk oxidation. In addition, this system allowed the observation of CO removal by the Eley-Rideal mechanism at high CO coverages, which facilitates further CO oxidation by triggering the CO removal by the Langmuir-Hinshelwood mechanism. Furthermore, effective CO management by this approach in practical applications was also verified by single-cell analysis.