Oxygen Reduction Reaction Activity and Durability for Pt/TaNx Model Catalysts Fabricated in Ultra-High-Vacuum

The electrochemical structural stability of Pt-shell/Ta nitride-core nanoparticles (Pt/TaNx NPs) on a highly oriented pyrolytic graphite (HOPG) substrate was investigated under the application of square-wave potential cycling in 0.1 M HClO4. The Pt/TaNx/HOPG samples were fabricated through arc-plasma deposition (APD) of TaNx NPs, followed by electron-beam evaporation of Pt in ultra-high vacuum (UHV). X-ray diffraction and X-ray photoelectron spectroscopy results present strong evidence of tantalum nitride generation by the APD of tantalum under the introduction of nitrogen (0.1 Pa) into the UHV chamber. Evaluation of the oxygen reduction reaction (ORR) activity of the catalysts after applying square-wave potential cycling between 0.6 and 1.0 V clearly shows that the nitridation of transition-metal cores is effective for improving the ORR activity and durability of core-shell type NP catalysts.