Boosting electrocatalytic performance and durability of Pt nanoparticles by conductive MO2−x (M = Ti, Zr) supports

Metal oxides, especially TiO2, have been studied as an alternative support to replace the carbon in the conventional Pt/C catalysts for their high electrochemical stability at high electrode potentials. The low conductivity of metal oxides has been a big hurdle. In this work, we successfully overcome this issue by forming conductive MO2−x (M = Ti and Zr) through solid state reduction with NaBH4. The temperature of the reaction has turned out to be a crucial parameter to obtain highly conductive MO2−x. Pt/MO2−x catalysts were prepared by depositing Pt nanoparticles (NPs) on MO2−x supports whose analysis data, show that the Pt NPs are uniformly deposited on the surface of MO2−x supports and that there is a strong electronic interaction between Pt NPs and MO2−x supports. The electrocatalysis of Pt/MO2−x catalysts for oxygen reduction reaction (ORR) has been studied. Pt/MO2−x catalysts show significantly enhanced mass activity (MA) and specific activity (SA) from those of Pt/C catalyst. More importantly, Pt/MO2−x catalysts show a superior long-term durability. After 50,000 cycles of durability test, Pt/T370 catalyst retains 75%/84% of initial MA/SA, and Pt/Z438 catalyst retains 81%/88% of initial MA/SA, while Pt/C catalyst keeps only 36%/56% of initial MA/SA after 30,000 cycles. The significantly enhanced ORR performance of Pt/MO2−x catalysts is attributed to the strong metal-support interaction (SMSI) effect between MO2−x and Pt NPs as well as the high conductivity of MO2−x supports. We believe Pt/MO2−x catalysts are a promising form of electrocatalysts that can replace the presently dominating but not quite satisfactory Pt/C in fuel cell applications.