Origin of Efficient Catalytic Combustion of Methane over Co₃O₄(110): Active Low-Coordination Lattice Oxygen and Cooperation of Multiple Active Sites

Abstract

A complete catalytic cycle for methane combustion on the Co3O4(110) surface was investigated and compared with that on the Co3O4(100) surface on the basis of first-principles calculations. It is found that the 2-fold coordinated lattice oxygen (O2c) would be of vital importance for methane combustion over Co3O4 surfaces, especially for the first two C–H bond activations and the C–O bond coupling. It could explain the reason the Co3O4(110) surface significantly outperforms the Co3O4(100) surface without exposed O2c for methane combustion. More importantly, it is found that the cooperation of homogeneous multiple sites for multiple elementary steps would be indispensable. It not only facilitates the hydrogen transfer between different sites for the swift formation of H2O to effectively avoid the passivation of the active low-coordinated O2c site but also stabilizes surface intermediates during the methane oxidation, optimizing the reaction channel. An understanding of this cooperation of multiple active sites not only might be beneficial in developing improved catalysts for methane combustion but also might shed light on one advantage of heterogeneous catalysts with multiple sites in comparison to single-site catalysts for catalytic activity.

Improved catalytic combustion of methane using CuO nanobelts with predominantly (001) surfaces

“…This is followed by O 2 dissociation which occurs over the vacancy with a maximum energy barrier of 0.91 eV. This is informative because it indicates that the key role of OV is to activate O 2 and release a highly active oxygen atom, although a barrier of 0.91 eV is found for O 2 dissociation in the case of CuO(001), but the dehydrogenation from CH x becomes exothermic, confirming the importance of surface oxygen and oxygen vacancies, as suggested by Hu et al [22] and Jin et al [28]. According to this understanding, the catalysis performance may be further improved by adding alloy elements or surface doping to reduce the barrier.…”

“…Among them, five are featured with mixed O/Cu surface atoms, except (001) which is fully covered by two-coordinated oxygen (O 2c ) before it is relaxed. Very recently, O 2c has been identified as an active site for CH 4 oxidation in the case of Co 3 O 4 whereby CuO(001) offers an ideal opportunity to test this hypothesis [22]. …”

Quantum Effects Allow the Construction of Two‐Dimensional Co3O4‐Embedded Nitrogen‐Doped Porous Carbon Nanosheet Arrays from Bimetallic MOFs as Bifunctional Oxygen Electrocatalysts

“…The Co 2p XPS spectrum is given in Figure d. The 2p 3/2 spectrum exhibits two peaks at 780.1 eV and 781.9 eV, whereas the 2p 1/2 spectrum has peaks at 795.6 eV and 797.4 eV, both corresponding to Co 3+ and Co 2+ , respectively. The weak satellite peaks in the Co 2p XPS spectrum confirms the typical spinel structure of Co 3 O 4 containing the different valences of the cobalt ion …”

“…The Co 2p XPS spectrum is given in Figure 5d.T he 2p 3/2 spectrum exhibits two peaks at 780.1 eV and7 81.9 eV,w hereas the 2p 1/2 spectrum has peaks at 795.6 eV and 797.4 eV,b oth corresponding to Co 3 + and Co 2 + ,r espectively.T he weak satellite peaks in the Co 2p XPS spectrum confirmst he typical spinel structure of Co 3 O 4 containing the different valences of the cobalt ion. [50] To investigate the specific surfacea rea and porous structure of the 2D-MCo 3 O 4 -NCNAs, N 2 adsorption/desorption analysis was performed. The isotherms of 2D-MCo 3 O 4 -NCNAs reveal a type IV isotherm (Figure 5e), indicating the presence of mesopores and micropores.…”

Trends of Alkane Activation on Doped Cobalt (II, III) Oxide from First Principles

“…It is well known that metal oxides with different surface facets contain oxygen sites with very different activities, which must be considered to predict the catalytic performance of a metal oxide. For example, Co 3 O 4 is active and stable for alkane oxidation and oxidative dehydrogenation under high temperatures . Depending on the synthesis and treatment method, Co 3 O 4 nanoparticles of different exposed surface facet orientations can be observed with different reactivities .…”