Improved performance of PtRu/C prepared by selective deposition of Ru on Pt as an anode for a polymer electrolyte membrane fuel cell

Ru-promoted Pt/C catalysts with different Ru/Pt ratios are prepared by selective chemical vapour deposition (CVD) of Ru onto a Pt surface. The optimum PtRu/C (Ru/Pt = 0.44) catalyst prepared using a CVD method shows improved performance as an anode for a polymer electrolyte membrane fuel cell in the presence of CO, as compared with a commercial PtRu/C (Ru/Pt = 1) catalyst and a PtRu/C (Ru/Pt = 1) catalyst prepared using a conventional impregnation (IMP) method. This observation is confirmed by the results of half-cell and single-cell tests. The CVD catalyst shows an improved CO tolerance because Ru is preferentially deposited as nano-scale particles on the Pt surface and, consequently, the number of Pt particles that are in close contact with the added Ru is greater in the CVD catalyst. An increase in the interfacial area between the Ru and the Pt facilitates the transfer of the oxygen-containing species to the CO-poisoned Pt surface such that the oxidation of CO is promoted. The Pt surface is also modified electronically due to an interaction with the added Ru, which is stronger in the CVD catalyst than in the IMP catalyst, as demonstrated by X-ray photoelectron analysis.