O2activation by core–shell Ru13@Pt42particles in comparison with Pt55particles: a DFT study

The reaction of O2 with a Ru13@Pt42 core-shell particle consisting of a Ru13 core and a Pt42 shell was theoretically investigated in comparison with Pt55. The O2 binding energy with Pt55 is larger than that with Ru13@Pt42, and O-O bond cleavage occurs more easily with a smaller activation barrier (E a) on Pt55 than on Ru13@Pt42. Protonation to the Pt42 surface followed by one-electron reduction leads to the formation of an H atom on the surface with considerable exothermicity. The H atom reacts with the adsorbed O2 molecule to afford an OOH species with a larger E a value on Pt55 than on Ru13@Pt42. An OOH species is also formed by protonation of the adsorbed O2 molecule, followed by one-electron reduction, with a large exothermicity in both Pt55 and Ru13@Pt42. O-OH bond cleavage occurs with a smaller E a on Pt55 than on Ru13@Pt42. The lower reactivity of Ru13@Pt42 than that of Pt55 on the O-O and O-OH bond cleavages arises from the presence of lower energy in the d-valence band-top and d-band center in Ru13@Pt42 than in Pt55. The smaller E a for OOH formation on Ru13@Pt42 than on Pt55 arises from weaker Ru13@Pt42-O2 and Ru13@Pt42-H bonds than the Pt55-O2 and Pt55-H bonds, respectively. The low-energy d-valence band-top is responsible for the weak Ru13@Pt42-O and Ru13@Pt42-OH bonds. Thus, the low-energy d-valence band-top and d-band center are important properties of the Ru13@Pt42 particle.