Three-Dimensionally Costabilized Metal Catalysts toward an Oxygen Reduction Reaction

Improving the long-term stability of metal catalysts is crucial to developing polymer electrolyte fuel cells (PEFCs). In this work, we first report an inorganic (TiO₂)-organic (perfluorosulfonic acid, PFSA) costabilized Pt catalyst supported on graphene nanosheets (GNS) (Pt-PFSA-TiO₂/GNS). Herein, TiO₂, as a robust wall, impedes the collision between the metal nanoparticles (NPs) in plane along the horizontal x and y axes, while PFSA mainly anchors the metal NPs to constrain detachment along the vertical z axis. The resulting catalyst displays higher oxygen reduction reaction (ORR) activity in comparison to that of commercial Pt/C. Significantly, the stability is particularly better than that of only PFSA- or TiO₂-decorated catalysts (Pt-PFSA/GNS or Pt-TiO₂/GNS) and far better than that of Pt/C. After 6000 potential cycles, the half-wave potential (E_1/2) of Pt-PFSA-TiO₂/GNS decreases by only 16 mV, far less than that of Pt/C (56 mV). The excellent electrochemical property of Pt-PFSA-TiO₂/GNS is predominantly attributed to the synergistic effect of PFSA and TiO₂ in costabilizing the Pt NP by anchoring and blocking Pt NPs in all three spatial directions. The structural dynamics and mechanism of enhanced properties are also discussed.