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The existing states of potassium species in K-doped Co3O4 catalysts and their influences on the activities for NO and soot oxidation

Abstract

Potassium-doped Co3O4 prepared via sol-gel method was pretreated by water washing, and subsequently the fresh and washed catalysts were compared with pure Co3O4 in order to investigate the existing states of potassium species and their influences on the activities for NO and soot oxidation. The samples were characterized by N2 adsorption-desorption, XRD, FT-IR, NOx-TPD, CO2-TPD, O2-TPD and XPS. It was found that two kinds of K species were existed in K-Co3O4, e.g. the “free” K and the “stable” K. The “free” K species, which was present as carbonates and nitrates with high mobility, could improve the contact state of catalyst-soot and thus accelerate soot oxidation significantly, but it also covered the active surface of Co3O4 severely and was adverse for NO oxidation. The “stable” K species, which interacted strongly with Co3O4 and acted as electronic and structural modifier, facilitated the formation of O-/O2- species and oxygen vacancies, exposed more surface Co3+ sites and increased amounts of the medium/strong basic sites, and as a result, enhanced the intrinsic activities of Co3O4 for soot and NO oxidation. Both of the K species improved the NOx storage capacities of Co3O4, and the NOx species adsorbed on medium/strong basic sites with appropriate stability, aroused by the effect of “stable” K, were more beneficial for soot oxidation than those adsorbed on “free” K with high stability.

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Publication details

The article was received on 18 Jul 2017, accepted on 09 Sep 2017 and first published on 11 Sep 2017


Article type: Paper
DOI: 10.1039/C7CY01444A
Citation: Catal. Sci. Technol., 2017, Accepted Manuscript
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    The existing states of potassium species in K-doped Co3O4 catalysts and their influences on the activities for NO and soot oxidation

    Z. Shang, M. Sun, X. Che, W. Wang, L. Wang, X. Cao, W. Zhan, Y. Guo, Y. Guo and G. Lu, Catal. Sci. Technol., 2017, Accepted Manuscript , DOI: 10.1039/C7CY01444A

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