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The relationship between the chemical state of Pd species and the catalytic activity for methane combustion on Pd/CeO2

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Abstract

Three Pd/CeO2 catalysts are synthesized by reduction-deposition and an impregnation method (IMP) to clarify how the chemical state of Pd influences the catalytic performance for CH4 combustion. The results show that Pd/CeO2 (HHA), using hydrazine hydrate as a reductant, shows much higher catalytic activity and stability for CH4 combustion than Pd/CeO2 (FA), using formaldehyde as a reductant, and Pd/CeO2 (IMP). The results of our comprehensive characterization reveal that there are two different chemical states of Pd species on Pd/CeO2: Pd2+ in the form of PdO particles and Pdδ+ (2 < δ ≤ 4) in the form of PdxCe1−xO2, and the latter is mainly induced by the Pd species entering the lattice of CeO2, which acts as a transfer channel of active oxygen species from the CeO2 lattice to active Pd species. The activity of Pd/CeO2 directly correlates to the surface concentrations of PdO and adsorbed oxygen. An increase in the amount of PdxCe1−xO2 would thicken the transition layer and decrease the replenishment rate of oxygen vacancies through diffusion of lattice oxygen. Meanwhile, the existence of more PdxCe1−xO2 could promote the capture of produced CO2 on the CeO2 around Pd species and decrease the catalytic activity.

Graphical abstract: The relationship between the chemical state of Pd species and the catalytic activity for methane combustion on Pd/CeO2

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Publication details

The article was received on 28 Jan 2018, accepted on 06 Apr 2018 and first published on 06 Apr 2018


Article type: Paper
DOI: 10.1039/C8CY00208H
Citation: Catal. Sci. Technol., 2018, Advance Article
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    The relationship between the chemical state of Pd species and the catalytic activity for methane combustion on Pd/CeO2

    J. Ma, Y. Lou, Y. Cai, Z. Zhao, L. Wang, W. Zhan, Y. Guo and Y. Guo, Catal. Sci. Technol., 2018, Advance Article , DOI: 10.1039/C8CY00208H

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