Relative Stabilities of M₁₃@Pt₄₂ Core-Shell Particle (M = 3d Transition Metals) and Its Non-Core-Shell Structure:...

Core-shell (CS) particle consisting of Pt shell and base metal core is one of promising candidates of excellent electrode catalyst for fuel cell, because it is highly active and highly stable like Pt particle but less expensive than Pt particle. However, its stability has been unclear. Herein, icosahedral M₁₃@Pt₄₂ (M = 3d transition metals, Sc to Cu) CS particles consisting of Pt₄₂ shell and M₁₃ core are systematically investigated using DFT calculations. The CS structures of Co₁₃@Pt₄₂, Ni₁₃@Pt₄₂, and Cu₁₃@Pt₄₂ are calculated to be more stable than their non-core-shell (NCS) structures in which one 3d metal atom of the M₁₃ core is exchanged with one Pt atom of the Pt₄₂ shell. For Sc₁₃Pt₄₂, Ti₁₃Pt₄₂, V₁₃Pt₄₂, Cr₁₃Pt₄₂, Mn₁₃Pt₄₂, and Fe₁₃Pt₄₂, on the other hand, the NCS structure is more stable than the CS one. Small deformation energy of the Pt₄₂ shell compared to that of the Pt₄₁M shell and small stabilization energy by Pt-M exchange between the Pt₄₂ shell and the M₁₃ core are particularly important for stabilizing the CS structure. Late 3d metal elements in the first transition series of the periodic table such as Co, Ni, and Cu are suitable for producing a stable M₁₃@Pt₄₂ CS particle because their electronegativities are larger than those of the early and middle 3d transition metal elements and their atomic sizes are smaller than those of the early 3d metal elements such as Sc and Ti atoms. O₂ adsorption to M₁₃@Pt₄₂ (M = Co, Ni, and Cu) CS particle occurs at the edge Pt atom and the vertex Pt atom in a side-on manner. The adsorption energies of O₂ molecule to Co₁₃@Pt₄₂, Ni₁₃@Pt₄₂, and Cu₁₃@Pt₄₂ CS particles are smaller than that to Pt₅₅ particle, indicating that the M₁₃ core decreases the reactivity of the Pt₄₂ shell for O₂ adsorption.