Reversible surface segregation of Pt in a Pt₃Au/C catalyst and its effect on the oxygen reduction reaction

Reversible surface segregation of Pt in Pt₃Au/C catalysts was accomplished through a heat treatment under a CO or Ar atmosphere, which resulted in surface Pt segregation and reversed segregation, respectively. The Pt-segregated Pt₃Au/C exhibited a significantly improved oxygen reduction reaction (ORR) activity (227 mA/mg_metal) compared to that of commercial Pt/C (59 mA/mg_metal). For the Pt-segregated Pt ₃Au/C, the increased OH-repulsive properties were validated by a CO bulk oxidation analysis and also by density functional theory (DFT) calculations. Interestingly, the DFT calculations revealed that the binding energy for Pt-segregated Pt₃Au (111) surfaces was 0.1 eV lower than that for Pt (111) surfaces, which has been previously reported to exhibit the optimum OH binding energy for the ORR. Therefore, the reversible surface segregation is expected to provide a practical way to control the surface states of Pt-Au bimetallic catalysts to enhance ORR activity. In addition, the Pt-segregated Pt₃Au/C showed excellent electrochemical stability, as evidenced by its high-performance retention (96.4%) after 10 000 potential cycles, in comparison to that of Pt/C (55.3%).