Cun-Qin Lv

Structure Sensitivity of CO Oxidation on Co3O4: A DFT Study

The reaction mechanism of CO oxidation on the Co(3)O(4) (110) and Co(3)O(4) (111) surfaces is investigated by means of spin-polarized density functional theory (DFT) within the GGA+U framework. Adsorption situation and complete reaction cycles for CO oxidation are clarified. The results indicate that 1) the U value can affect the calculated energetic result significantly, not only the absolute adsorption energy but also the trend in adsorption energy; 2) CO can directly react with surface lattice oxygen atoms (O(2f)/O(3f)) to form CO(2) via the Mars-van Krevelen reaction mechanism on both (110)-B and (111)-B; 3) pre-adsorbed molecular O(2) can enhance CO oxidation through the channel in which it directly reacts with molecular CO to form CO(2) [O(2)(a)+CO(g)→CO(2)(g)+O(a)] on (110)-A/(111)-A; 4) CO oxidation is a structure-sensitive reaction, and the activation energy of CO oxidation follows the order of Co(3)O(4) (111)-A(0.78 eV)>Co(3)O(4) (111)-B (0.68 eV)>Co(3)O(4) (110)-A (0.51 eV)>Co(3)O(4) (110)-B (0.41 eV), that is, the (110) surface shows higher reactivity for CO oxidation than the (111) surface; 5) in addition to the O(2f), it was also found that Co(3+) is more active than Co(2+), so both O(2f) and Co(3+) control the catalytic activity of CO oxidation on Co(3)O(4), as opposed to a previous DFT study which concluded that either Co(3+) or O(2f) is the active site.

The Mechanism of Low‐Temperature CO Oxidation on IB Group Metals and Metal Oxides

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 studied by means of density functional theory calculations with the aim to shed light on the reaction mechanism and catalytic activity of metals and metal oxides. The calculated results show that 1) the molecular oxygen mechanism is favored on Ag(111) and Au(111), but the atomic oxygen mechanism is favored on Cu(111); 2) the metal‐terminated metal oxide shows very low activity for CO oxidation; 3) the lattice oxygen can react either with gas phase CO or the absorbed CO molecule on oxygen‐terminated metal oxides; and 4) the reaction barrier for CO oxidation follows the order of M2O(100)–O

Reaction mechanism of methylamine decomposition on Ru(0001): a density functional theory study.

AbstractThe reaction mechanism of methylamine decomposition on Ru(0001) has been systematically investigated by density functional theory slab calculations. The decomposition network has also been described. The adsorption energies under the most stable configuration of the possible species and the energy barriers of the possible elementary reactions involved are obtained. Desorption is preferred for adsorbing methylamine and hydrogen, whereas for the other species, decomposition is more favorable. Our calculated results show that methylamine decomposition on Ru(0001) starts with H2CNH2 formation from methyl dehydrogenation, followed by subsequent methylene dehydrogenation, bond breaking of N–H and C–N in HCNH2, CH dehydrogenation and C–N bond cleavage in HCNH, and dehydrogenation of NH2, NH, and CH. FigureThe decomposition of methylamine was investigated on Ru(0001) surface, and HCNH2 and HCNH are the likely species to break C-N bond

Adsorption and decomposition of methylamine on a Pt(100) surface: a density functional theory study

The decomposition mechanisms of methylamine on a Pt(100) surface have been systematically investigated using density functional theory calculations. The most stable configurations and the corresponding adsorption energies for all the possible species involved were obtained, and the decomposition network was mapped out based on the energy barriers of the possible elementary reactions involved in methylamine decomposition. Desorption is preferred for adsorbing methylamine and hydrogen, whereas for the other species decomposition is more favorable. The most likely pathway for methylamine decomposition on Pt(100) is H3CNH2 → H2CNH2 + H → H2CNH + 2H → HCNH + 3H → HCN + 4H → HCN + 5H → CN + 5/2H2(g), which is different from the reaction mechanism on Pt(111), which is H3CNH2 → H3CNH → H3CN → H2CN → HCN.

Chemisorbed oxygen atom on the activation of C–H bond in methane: a Rh model study

Single atom catalysts usually show unique catalytic activity and the physical nature is not clear. In the present work, density functional theory calculations are presented for adsorption and dissociation of CH4 on clean and oxygen atom pre-adsorbed Rh metal surfaces with different coordinate numbers such as (111), (100), (110), (211), kink, ad-row (add two atoms on a p(2 × 2)-111 unit cell) and ad-atom (add one atom on a p(2 × 2)-111 unit cell). The present calculation results show that the pre-adsorbed oxygen atom inhibits the methane dehydrogenation on Rh surfaces in general except on the ad-atom model where it has no effect, thus resulting in the possibility of the partial oxidation of methane to produce syngas (the mixture of CO and H2) on Rh ad-atom catalysts. Having been analyzed by the barrier decomposition method, it was found that the presence of an oxygen atom usually reduces the adsorption energy of dissociated fragments and increases the interaction between the dissociated fragments, both of which lead to an increase of the reaction barrier. Moreover, the electronic analysis indicated that the oxygen effect can be attributed to the strong interaction of acid–base pair sites on oxygen–metal systems, and a strong acid–base interaction related to the low dehydrogenation barrier.