Comparison of iridium– and ruthenium–based, Pt–surface–enriched, nanosize catalysts for the oxygen–reduction reaction

• We compared ORR activity of Pt–Surface–Enriched and 50%Pt/C catalysts.
• The Pt–Surface–Enriched structure was confirmed by STEM EDS and XPS.
• Of the compared catalysts, the Ir–based catalyst showed the highest ORR activity.
• Pt–Surface–Enriched catalysts can be alternative to platinum catalysts.

Pt–surface–enriched nanosize catalysts (Pt–SENS catalysts) with ruthenium and iridium cores, supported on XC72, were synthesized and characterized. The structure and composition of the catalysts are determined by Energy–Dispersive X–ray Spectroscopy (EDS), X–ray Photoelectron Spectroscopy (XPS), Scanning Transmission Electron Microscopy (STEM) and X–Ray Diffraction (XRD). Electrochemical characterization tests, including oxygen-reduction-catalysis activity and durability studies of catalysts are performed with the use of cyclic–voltammetry and rotating–disk–electrode (RDE) techniques at room temperature. The ORR activity of the homemade catalysts is also compared to ORR activity of commercial 50%Pt/C catalyst. It is determined that the Ir–based catalyst (Pt/Ir/XC72) shows higher ORR activity in terms of A g−1 of Pt (at 0.85 V vs. RHE) than the Ru–based catalyst (Pt/Ru/XC72) and the commercial 50%Pt/C. The Ru–based catalyst shows similar ORR activity in terms of A g−1 of Pt, to that of the commercial 50%Pt/C, but with much lower durability.