O(2) activation by core–shell Ru(13)@Pt(42) particles in comparison with Pt(55) particles: a DFT study

The reaction of O(2) with a Ru(13)@Pt(42) core–shell particle consisting of a Ru(13) core and a Pt(42) shell was theoretically investigated in comparison with Pt(55). The O(2) binding energy with Pt(55) is larger than that with Ru(13)@Pt(42), and O–O bond cleavage occurs more easily with a smaller activation barrier (E(a)) on Pt(55) than on Ru(13)@Pt(42). Protonation to the Pt(42) 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 O(2) molecule to afford an OOH species with a larger E(a) value on Pt(55) than on Ru(13)@Pt(42). An OOH species is also formed by protonation of the adsorbed O(2) molecule, followed by one-electron reduction, with a large exothermicity in both Pt(55) and Ru(13)@Pt(42). O–OH bond cleavage occurs with a smaller E(a) on Pt(55) than on Ru(13)@Pt(42). The lower reactivity of Ru(13)@Pt(42) than that of Pt(55) 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 Ru(13)@Pt(42) than in Pt(55). The smaller E(a) for OOH formation on Ru(13)@Pt(42) than on Pt(55) arises from weaker Ru(13)@Pt(42)–O(2) and Ru(13)@Pt(42)–H bonds than the Pt(55)–O(2) and Pt(55)–H bonds, respectively. The low-energy d-valence band-top is responsible for the weak Ru(13)@Pt(42)–O and Ru(13)@Pt(42)–OH bonds. Thus, the low-energy d-valence band-top and d-band center are important properties of the Ru(13)@Pt(42) particle.