Reversible Surface Segregation of Pt in a Pt₃Au/C Catalyst and Its Effect on the Oxygen Reduction Reaction

Abstract

Reversible surface segregation of Pt in Pt 3 Au/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 Pt 3 Au/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 3 Au/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 Pt 3 Au (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 Pt 3 Au/C showed excellent electrochemical stability, as evidenced by its highperformance retention (96.4%) after 10 000 potential cycles, in comparison to that of Pt/C (55.3%).

Recent advancements in Pt and Pt-free catalysts for oxygen reduction reaction

“…The dissolution of the non-noble 3d transition metal leaves behind an atomically rough surface composed of Pt atoms with low/no lateral coordination. 208 The Pt-segregated Pt 3 Au/C exhibited a significantly improved ORR activity (227 mA mg metal À1 ) compared to that of commercial Pt/C (59 mA mg metal À1 ). 29,200,201 Another 14 Illustration of basic synthesis approaches for the preparation of coreshell nanoparticle catalysts.…”

First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

“…After heating the catalyst in a CO atmosphere or cycling it into the oxide formation region, the observed activity was greater than that on Pt. 26,28,[31][32][33][34] The activity enhancement was attributed to a reversible surface segregation of Pt induced by CO or O adsorbates. Au has a low surface energy and thus naturally prefers to be on the surface.…”

Borohydride electrooxidation over Pt/C, AuPt/C and Au/C catalysts: Partial reaction pathways and mixed potential formation

“…The less pronounced hydrogen and oxygen adsorption/desorption features in the AuPt/C base voltammetry (Fig. 1c, dotted line) compared to Pt/C were explained by the lower number of Pt surface sites and a weaker binding of OH ad on the bimetallic surface [20]. The absence of deuterium formation in the BOR on the AuPt/C catalyst up to ca.…”