The First Principle Study Of CO Adsorption And Reaction On Transition Metal And Metal Oxide Surfaces

In this thesis, based on the first principle quantum mechinism calculations, the adsorption and oxidation of CO on different Co3O4 surfaces and IB group metal and metal oxide surfaces have been systemically investigated by DFT-GGA method and periodical slab model. At the same time, the adsorption and dissociation of H2O on transition metal oxides have also been studied in detail. The equilibrium structure, the most stable adsorption site, the adsorption strength, the transition state and the activation barrier have been systemically studied. At the molecular level, the essence of the complicated catalytic reaction is expored, validate the experimental rules and expect to provide theoretical guidance for experiments.1. The oxidation of CO on Co3O4(110) and Co3O4(111) surfaces have been studied in detail by the density functional theory calculations. Since cobalt oxide has highly correlated electronic states, it is necessary to consider Coulumb (U) and exchange (J) interactions. So CO oxidation on the Co3O4(110) and Co3O4(111) surfaces is investigated by means of spin polarized density functional theory within the GGA+U framework. The adsorption of the molecular CO, oxygen atom, molecular O2 and CO2 molecule as well as the activation barriers is investigated. The calculated results indicate that i) reaction mechanism of CO(g)+O(lattice)→CO2(g) is favored at high CO coverage, while the reaction mechanism of CO(a)+O(a)→CO2(g) is favored at low CO coverage; ii) the CO oxidation is a structure-sensitive reaction, namely, the activity of (110) surface is higher than that of (111) surace; ii) Co3+ is the active site for CO oxidation on Co3O4; and iv) the coverage of CO plays an important role in CO oxidation on different Co3O4 surfaces.2. CO oxidation on the IB group metals (Cu (111), Ag (111) and Au (111)) and corresponding metal oxides (Cu2O (100), Ag2O (100) and Au2O (100)) has been systemically studied by means of density functional theory calculations, aiming at shedding light on the catalytic activity of metals and metal oxides and exploring the difference of catalytic activity between metal oxides and their corresponding metals. The calculated results show that (i) CO oxidation on Ag (111) surface exhibits higher activity than that on Cu (111) and Au (111) surfaces, and (ii) CO oxidation on Ag2O (100) surface exhibits higher activity than that on Cu2O (100) and Au2O (100) surfaces, (iii) both Eley-Rideal and Langmuir-Hinshelwood reaction mechanisms can take place on oxygen-terminated metal oxides, (iv) the activation barrier follows the order of M2O (100)-O< M (111)< M2O (100)-M (M=Cu, Ag, Au), namely metal oxides (M2O (100)-O) shows higher activity than corresponding metals, and v) the detailed analysis of the calculated results indicates that the interaction energy between two adsorbed species at the transition state plays an important role in determining the trend in the barrier.3. A period self-consistent DFT calculation is performed to investigate the adsorption and dissociation of H2O on IB group metal oxide M2O (100) (M=Cu, Ag, Au). At the same time, the adsorption and dissociation H2O on the transition metal oxide MO2 (100) (M=Ru, Rh, Pd) have also been in detail investigated. The calculated results reveal that i) two different reaction paths are proposed: one is H2O (a)→OH (a)+H (a) and H2O (a)+O (lattice)→2OH (a) on M2O (100) (M=Cu, Ag, Au) surfaces, one is H2O (a)+O (lattice)→2OH (a) and H2O (a)+O (a)→2OH (a) on MO2 (100) (M=Ru, Rh, Pd) surfaces; ii) the second reaction path is favoured of molecular H2O dissociation on M2O (100) (M=Cu, Ag, Au) surfaces; iii) the dissociation of molecular H2O on MO2 (100) (M=Ru, Rh, Pd) surfaces is spontaneous process.