Search

This work clearly disclosed that the lower energy d-valence band-top of M 13 @Pt 42 is the origin of the higher activity of the M 13 @Pt 42 , which arises from the smaller exchange repulsion of the Pt 42 shell with the M 13 core than with the Pt 13 core. [Display omitted] • Ni 13 @Pt 42 and Co 13 @Pt 42 are more active than Pt 55 for oxygen reduction reaction. • Rate-determining step is OH formation in Ni 13 @Pt 42 and Co 13 @Pt 42. • Rate-determining step is H 2 O formation in Pt 55. • Ni 13 and Co 13 cores accelerate H 2 O formation to enhance ORR catalytic activities. • Lower energy d-valence band-top leads to higher activity for ORR. Oxygen reduction reaction (ORR) by Pt 55 and core-shell M 13 @Pt 42 (M Co or Ni) particles is explored theoretically. Rate-determining step (RDS) is the second OH formation in M 13 @Pt 42 but the second H 2 O formation in Pt 55. Activation energy of RDS decreases following the order Pt 55 > Co 13 @Pt 42 > Ni 13 @Pt 42 and onset potential is larger in M 13 @Pt 42 than in Pt 55 , showing M 13 @Pt 42 is more active than Pt 55. Lower energy d-valence band-top (φ VB-top) of M 13 @Pt 42 results in the higher activity of M 13 @Pt 42 than that of Pt 55 , where φ VB-top is the highest energy peak in d-valence band DOS. Thus, the φ VB-top energy is important for ORR activity. The lower energy φ VB-top of M 13 @Pt 42 than that of Pt 55 mainly arises from smaller exchange repulsion of Pt 42 shell with M 13 core than that with Pt 13 core; smaller atomic size and d orbital size of Co and Ni than those of Pt are key factors. [ABSTRACT FROM AUTHOR]