Relativistic and dispersion effects on O2 activation by metallic nanoparticles

In a recent study from KAUST, the effects of relativity and dispersion interactions were quantified for O2 adsorption and dissociation on Cu38, Ag38 and Au38 nanoparticles (NPs).The results indicate that the barrier for O2 dissociation almost negligible on Cu38, while the barrier on Ag38 is close to 20 kcal/mol, decreasing again to 10 kcal/mol for the heaviest congener, Au38.

The behavioral trend for the coinage metals is analyzed to quantify the impact of relativity and of dispersion interactions through a comparison of nonrelativistic, scalar-relativistic, and dispersion corrected DFT methods. Nonrelativistic calculations show a clear trend down the triad: the larger NPs bind O2 more weakly, resulting in higher O2 dissociation barriers. Inclusion of relativity has no impact on the O2 adsorption energy, but it does reduce the energy barrier for O2 dissociation on Au38. Dispersion interactions have a remarkable role in improving the adsorption energy of O2 on the heavier Ag38 and especially Au38 NPs.

O2 Activation on metallic NPs: relativistic and dispersion effects

(a) Projected density of states for O2 dissociation on at the NR and SR level on Au38, (b) Reaction pathways for O2 dissociation on the Cu38, Ag38, and Au38 NPs, (c-d) Electron density difference maps and Representation of key structures along the reaction pathway for O2 dissociation on the Au38 NP at the SR level

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Dispersion, relativistic effects, catalysis, nanoparticles

M. B. Kanoun and L. Cavallo, Quantifying the Impact of Relativity and of Dispersion Interactions on the Activation of Molecular Oxygen Promoted by Noble Metal Nanoparticles, J. Phys. Chem. C, 118, 13707–13714 (2014)

Key concepts