Effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria: Soot-ceria contact and interfacial oxygen evolution

Peng Liu; Xiaoliang Liang; Yanliu Dang; Junkai He; Alireza Shirazi-Amin; Laura A Achola; Shanka Dissanayake; Hanlin Chen; Mingli Fu; Daiqi Ye; Steven L Suib

doi:10.1016/j.jes.2020.08.026

Effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria: Soot-ceria contact and interfacial oxygen evolution

J Environ Sci (China). 2021 Mar:101:293-303. doi: 10.1016/j.jes.2020.08.026. Epub 2020 Sep 9.

Authors

Peng Liu¹, Xiaoliang Liang², Yanliu Dang³, Junkai He³, Alireza Shirazi-Amin⁴, Laura A Achola⁴, Shanka Dissanayake⁴, Hanlin Chen⁵, Mingli Fu⁶, Daiqi Ye⁶, Steven L Suib⁷

Affiliations

¹ School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, USA; University of Chinese Academy of Sciences, Beijing 100049, China.
² CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: liangxl@gig.ac.cn.
³ Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, USA.
⁴ Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, USA.
⁵ Guangdong Provincial Key Laboratory of Petrochemical Pollution Processes and Control, School of Environmental Science and Engineering, Guangdong University of Petrochemical Technology, Maoming 525000, China.
⁶ School of Environment and Energy, South China University of Technology, Guangzhou 510006, China.
⁷ Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, USA; Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, USA. Electronic address: steven.suib@uconn.edu.

PMID: 33334524
DOI: 10.1016/j.jes.2020.08.026

Abstract

Ceria is widely used as a catalyst for soot combustion, but effects of Zr substitution on the reaction mechanism is ambiguous. The present work elucidates effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria. The nanostructured CeO₂, Ce_0.92Zr_0.08O₂, and Ce_0.84Zr_0.16O₂ composed of 5-6 nm crystallites display T_m-CO2 (the temperature at maximum CO₂ yield) at 383, 355, and 375°C under 10 vol.% O₂/N₂, respectively. The size of agglomerate decreases from 165.5 to 51.9-57.3 nm, which is beneficial for the soot-ceria contact. Moreover, Zr increases the amount of surface oxygen vacancies, generating more active oxygen (O₂^- and O^-) for soot oxidation. Thus, the activities of Ce_0.92Zr_0.08O₂ and Ce_0.84Zr_0.16O₂ in soot combustion are better than that of CeO₂. Although oxygen vacancies promote the migration of lattice O^2-, the enriched surface Zr also inhibits the mobility of lattice O^2-. Therefore, the T_m-CO2 of Ce_0.84Zr_0.16O₂ is higher than that of Ce_0.92Zr_0.08O₂. Based on reaction kinetic study, soot in direct contact with ceria preferentially decomposes with low activation energy, while the oxidation of isolated soot occurs through diffusion with high activation energy. The obtained findings provide new understanding on the soot combustion over nanoceria.

Keywords: Nanoceria; Oxygen mobility; Reaction kinetic; Soot combustion; Zr substitution.

MeSH terms

Catalysis
Cerium*
Oxygen
Soot*

Substances

Soot
Cerium
ceric oxide
Oxygen