An improved understanding of the interactions of transition-metal (TM) nanoparticles with Lewis acids/bases will facilitate the design of more efficient catalysts. Therefore, Pt-14, Pt-13, Pt-12, and Ni-12 nanoparticles have been studied at the TPSSh/Def2-TZVP level of density functional theory (DFT). Surface electrostatic potential [V-S(r)] maps are used to analyze the Lewis acidic and basic properties of all nanoparticles and indicate that the interactions of Pt and Ni nanoparticles are governed by sigma(d)-holes and sigma(s) -holes, respectively. Lewis acids (Na+, HF) and a Lewis base (H2O) have been tested as ligands to probe the local interaction proficiencies. The comparison between binding energies and V-S(r) shows that the lowest minimum (V-S,V-min) and highest maximum (V-S,V-max) of V-S(r) on each particle can predict the most favorable binding site for the Lewis acids and base, respectively. V(S,min )can also rank the different binding strengths of Na+ and HF with the nanoparticles. For H2O, the binding strength versus V-S,V-max correlation is better for Ni-12 than for the Pt nanoparticles. This observation is discussed in relation to charge transfer/polarization and structural deformation upon interaction. In light of our findings, we compare the catalytic potential of Ni to the less abundant but more commonly used Pt.

Two local reactivity descriptors computed by Kohn-Sham density functional theory (DFT) are used to predict and rationalize interactions of nucleophilic molecules (exemplified by CO and H2O) with transition metal (TM) and oxide surfaces. The descriptors are the electrostatic potential, V-S(r), and the local electron attachment energy, E-S(r), evaluated on surfaces defined by the 0.001 e Bohr(-3) isodensity contour. These descriptors have previously shown excellent abilities to predict regioselectivity and rank molecular as well as nanoparticle reactivities and interaction affinities. In this study, we generalize the descriptors to fit into the framework of periodic DFT computations. We also demonstrate their capabilities to predict local surface propensity for interaction with Lewis bases. It is shown that E-S(r) and V-S(r) can rationalize the interaction behavior of TM oxides and of fcc TM surfaces, including low-index, stepped and kinked surfaces spanning a wide range of interaction sites with varied coordination environments. Broad future applicability in surface science is envisaged for the descriptors, including heterogeneous catalysis and electrochemistry.

The Cu2O(100) surface is most favorably terminated by a (3,0;1,1) reconstruction under ultrahigh-vacuum conditions. As most oxide surfaces, it exhibit defects, and it is these sites that are focus of attention in this study. The surface defects are identified, their properties are investigated, and procedures to accurately control their coverage are demonstrated by a combination of scanning tunneling microscopy (STM) and simulations within the framework of density functional theory (DFT). The most prevalent surface defect was identified as an oxygen vacancy. By comparison of experimental results, formation energies, and simulated STM images, the location of the oxygen vacancies was identified as an oxygen vacancy in position B, located in the valley between the two rows of oxygen atoms terminating the unperturbed surface. The coverage of defects is influenced by the surface preparation parameters and the history of the sample. Furthermore, using low-energy electron beam bombardment, we show that the oxygen vacancy coverage can be accurately controlled and reach a complete surface coverage (1 per unit cell or 1.8 defects per nm(2)) without modification to the periodicity of the surface, highlighting the importance of using local probes when investigating oxide surfaces.