Growth mechanism of palladium clusters on rutile TiO_2 (110) surface

Oxide-supported transition metal systems have been the subject of enormous interest due to the improvement of catalytic properties relative to the separate metal.Thus in this paper,we embark on a systematic study for Pd n （n=1-5） clusters adsorbed on TiO2 （110） surface based on DFT-GGA calculations utilizing periodic supercell models.A single Pd adatom on the defect-free surface prefers to adsorb at a hollow site bridging a protruded oxygen and a five-fold titanium atom along the [110] direction,while Pd dimer is located on the channels with the Pd-Pd bond parallel to the surface.According to the transition states （TSs） search,the adsorbed Pd trimer tends to triangular growth mode,rather than linear mode,while the Pd4 and Pd5 clusters prefer three-dimensional （3D） models.However,the oxygen vacancy has almost no influence on the promotion of Pd n cluster nucleation.Additionally,of particular significance is that the Pd-TiO2 interaction is the main driving force at the beginning of Pd nucleation,whereas the Pd-Pd interaction gets down to control the growth process of Pd cluster as the cluster gets larger.It is hoped that our theoretical study would shed light on further designing high-performance TiO2 supported Pd-based catalysts.

Density functional theory study of CO catalytic oxidation on Co_2B_2/TiO_2(110) surface

Titanium dioxide with CoB amorphous alloys nanoparticles deposited on the surface is known to exhibit higher catalytic activity than the CoB amorphous.A study of the structure of such system is necessary to understand this effect.A quantum chemical study of Co2B2 on the TiO2（110） surface was studied using periodic slab model within the framework of density functional theory（DFT）.The results of geometry optimization indicated that the most stable model of adsorption was Co2B2 cluster adsorbed on the hollow site of TiO2 .The adsorption energy calculated for Co2B2 on the hollow site was 439.3 kJ/mol.The adsorption of CO and O2 was further studied and the results indicated that CO and O2 are preferred to adsorb on the Co2 site.Co-adsorption of CO and O2 shows that Co2B2 /TiO2 is a good catalyst for the oxidation of CO to carbon dioxide in the presence of oxygen.

Study of CO adsorption on perfect and defective pyrite (100) surfaces by density functional theory

First-principles calculations based on density functional theory （DFT） and the generalized gradient approximation （GGA） have been used to study the adsorption of CO molecule on the perfect and defective FeS 2 （100） surfaces. The defective Fe 2 S（100） surfaces are caused by sulfur deficiencies. Slab geometry and periodic boundary conditions are employed with partial relaxations of atom positions in calculations. Two molecular orientations, Cand O-down, at various distinct sites have been considered. Total energy calculations indicated that no matter on perfect or deficient surfaces, the Fe position is relatively more favored than the S site with the predicted binding energies of 120.8 kJ/mol and 140.8 kJ/mol, respectively. Moreover, CO was found to be bound to Fe atom in vertical configuration. The analysis of density of states and vibrational frequencies before and after adsorption showed clear changes of the C–O bond.