Pt₃Ti (Ti₁₉@Pt₆₀)-Based Cuboctahedral Core–Shell Nanocluster Favors a Direct over Indirect Oxygen Reduction Reaction

Developing a highly efficient catalyst with lower Pt content for the oxygen reduction reaction (ORR) is highly sought for fuel cell applications. The potential applicability of a cuboctahedral core–shell (Ti 19 @Pt 60 ) nanocluster (NC) toward ORR activity has been investigated and compared with that of a pure Pt NC (Pt 79 ). The energetic stability, thermal stability, and dissolution limit of Ti 19 @Pt 60 NCs has been investigated for their possible synthesis and practical usages. Thermodynamic and kinetic parameters are explored to find out the most favored ORR pathway and product selectivity on the Ti 19 @Pt 60 NC. Rate-determining steps (*O 2 activation and *OH formation) are highly improved over the Ti 19 @Pt 60 NC with respect to the cuboctahedral Pt NC (Pt 79 ), pure metal (Pt, Pd, and Ag), and alloy (Pt 3 M; M = Ni, Co, Ti) based catalysts. Our detailed investigation reveals that the *O 2 -induced structural changes favor direct *O 2 dissociation on the Ti 19 @Pt 60 NC surface. Further, we find that a dual mechanism (ligand effect and charge transfer) plays an important role to improve the ORR activity. The results obtained in this study provide fundamental insight into the role of a core–shell NC toward ORR activity.