The role of oxygen during the catalytic oxidation of ammonia on Co3O4(100)

作者：Shojaee Kambiz; Haynes Brian S; Montoya Alejandro^*

来源：Applied Surface Science, 2014, 316: 355-365.

DOI：10.1016/j.apsusc.2014.08.021

• Cobalt oxide
• Ammonia dehydrogenation
• Reaction mechanism

The adsorption selectivity and dehydrogenation energy barriers of NH3, NH2 and NH on the (1 0 0) surface planes of Co3O4 are determined by means of density functional methods. Stepwise hydrogen abstraction is effected by lattice O-3o associated with octahedrally coordinated surface Co atoms. The final H-abstraction, from NH, leads directly to the formation of gaseous product NO with the creation of a lattice oxygen vacancy. Reaction of this vacancy with gas-phase O-2 repairs the vacancy and creates surface-adsorbed O* which is also capable of abstracting H from NH3*, NH2* and NH*, the final step leading to directly again to NO formation. The mobile surface OH* formed from the O*-mediated abstraction steps is also capable of abstracting H from the NHx* species, leading ultimately to surface N* which then easily extracts a lattice O-3o to form NO and a new vacancy. The overall mechanism to form NO is a complex cycle of lattice-and surface-mediated abstractions. The hydrogen budget in the reaction shows corresponding complexity. Surface H* (formed when lattice O-3o abstracts H from NHx) is stable and immobile but it can be abstracted by surface OH* to form water. OH* disproportionation reaction also forms water.

• 出版日期2014-10-15