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Following our strategy to analyze the metal–support interaction, we present periodic DFT calculations for adsorption of metal atoms on a perfect rutile TiO2(110) surface (at low coverage, θ = 1/3) to investigate the interaction of an individual metal atom, M, with TiO2 and its consequence on the coadsorption of H and CO over M/TiO2. M under investigation varies in a systematic way from K to Zn. It is found that the presence of the support decreases or increases the strength of M–H or M–CO interaction according to the nature of M. The site of the adsorption for H and the formation of HCO/M also depend on M. From the left- to the right-hand side of the period, C and O both interact while O progressively detaches from M. On the contrary, for M = Fe–Cu, CO dissociation is more likely to happen. For CO and H coadsorption, two extreme cases emerge: For Ni, the hydrogen adsorbed should easily move on the support and CO dissociation is more likely. For Ti or Sc, H is easily coadsorbed with CO on the metal and CO hydrogenation could be the initial step. [ABSTRACT FROM AUTHOR]

Highlights: [•] K–Zn, Pd, Ir and Pt atoms interact weakly with TiO2 oxygen defective surface compared to the perfect surface. [•] They preferentially adsorb out of the oxygen vacancy. [•] Gold is different with a strong adsorption in the vacancy; then, Au is in a reduced state. [ABSTRACT FROM AUTHOR]

Abstract: We present periodic DFT calculations for studying the effect of a rutile-TiO2(110) support on the interaction of H with a metal atom M, M K to Zn. For some metals, the surface support gives a decrease of the M–H interaction strength as usually associated with SMSI. On the contrary for others, we show that the M–H interaction is enhanced by the presence of the support. Both M–H and M-support interactions are strong when each of them is associated with a strongly exothermic transfer of at least one electron, requesting the transfer of at least two electrons. [Copyright &y& Elsevier]

We performed periodic DFT calculations for adsorption of metal atoms on a perfect rutile TiO(110) surface (at low coverage, θ = 1/3) to investigate the interaction of an individual metal atom with TiO and to compare it with a study previously done on MgO(100). We considered partial period of Mendeleev's table from K to Zn. The overall evolution of the adsorption energies shows two maxima as for MgO(100). Two main differences, however, exist: the adsorption energy is much stronger and the first maximum is enhanced relative to the second one. This is attributed to the reducibility of the surface titanium cation. When the adsorbed metal is electropositive, it is oxidized under adsorption transferring electrons to titanium cations. We present the effect of introducing a Hubbard term to the gradient-corrected approximation band-structure Hamiltonian (GGA + U). The introduction of a reasonable Hubbard correction preserves the trends and allows localizing the electron of the reduction on Ti atoms in the near surface region. Finally, our results conclude that for heavier M atoms of the period, insertion is energetically favored relative to adsorption. [ABSTRACT FROM AUTHOR]

Abstract: Convergence of rutile-TiO2(110) surface properties with the slab thickness, which imposes very thick slabs when all the atomic positions are optimized, is achieved more rapidly when one face of the slab is saturated. We report calculations using PW91 functional and plane-wave pseudopotential methodology showing that saturation by dissociated H2O of the ‘bottom face’ improves convergence for the estimation of the surface energy for the ‘top face’. The description of the adsorption on top of a Ti site on this face is upgraded. The electronic band gap is enlarged, becoming closer to the value obtained on thick slabs by complete optimization. [Copyright &y& Elsevier]