Enhanced Intermediate-Temperature CO2 Splitting Using Nonstoichiometric Ceria and Ceria-Zirconia

Handle URI:
http://hdl.handle.net/10754/625793
Title:
Enhanced Intermediate-Temperature CO2 Splitting Using Nonstoichiometric Ceria and Ceria-Zirconia
Authors:
Zhao, Zhenlong; Uddi, Mruthunjaya; Tsvetkov, Nikolai; Yildiz, Bilge; Ghoniem, Ahmed F.
Abstract:
CO2 splitting via thermo-chemical or reactive redox has emerged as a novel and promising carbon-neutral energy solution. Its performance depends critically on the properties of the oxygen carriers (OC). Ceria is recognized as one of the most promising OC candidates, because of its fast chemistry, high ionic diffusivity, and large oxygen storage capacity. The fundamental surface ion-incorporation pathways, along with the role of surface defects and the adsorbates remains largely unknown. This study presents a detailed kinetics study of CO2 splitting using CeO2 and Ce0.5Zr0.5O2 (CZO) in the temperature range 600-900℃. Given our interest in fuel-assisted reduction, we limit our study to relatively lower temperatures to avoid excessive sintering and the need for high temperature heat. Compared to what has been reported previously, we observe higher splitting kinetics, resulting from the utilization of fine particles and well-controlled experiments which ensure a surface-limited-process. The peak rates with CZO are 85.9 μmole g–1s–1 at 900℃ and 61.2 μmole g–1s–1 at 700℃, and those of CeO2 are 70.6 μmole g–1s–1 and 28.9 μmole g–1s–1. Kinetics models are developed to describe the ion incorporation dynamics, with consideration of CO2 activation and the charge transfer reactions. CO2 activation energy is found to be – 120 kJ mole-1 for CZO, half of that for CeO2, while CO desorption energetics is analogous among the two samples with the value of ~160 kJ mole-1. The charge-transfer process is found to be the rate-limiting step for CO2 splitting. The evolution of CO32- with surface Ce3+ is examined based on the modeled kinetics. We show that the concentration of CO32- varies with Ce3+ in a linear-flattened-decay pattern, resulting from a mismatch between the kinetics of the two reactions. Our study provides new insights into the significant role of the surface defects and adsorbates in determining the splitting kinetics.
Citation:
Zhao Z, Uddi M, Tsvetkov N, Yildiz B, Ghoniem AF (2017) Enhanced intermediate-temperature CO2 splitting using nonstoichiometric ceria and ceria–zirconia. Phys Chem Chem Phys 19: 25774–25785. Available: http://dx.doi.org/10.1039/c7cp04789d.
Publisher:
Royal Society of Chemistry (RSC)
Journal:
Phys. Chem. Chem. Phys.
Issue Date:
24-Aug-2017
DOI:
10.1039/c7cp04789d
Type:
Article
ISSN:
1463-9076; 1463-9084
Sponsors:
This study is financially supported by a grant from the British Petroleum (BP) and the King Abdullah University of Science and Technology (KAUST) Investigator Award.
Appears in Collections:
Publications Acknowledging KAUST Support

Full metadata record

DC FieldValue Language
dc.contributor.authorZhao, Zhenlongen
dc.contributor.authorUddi, Mruthunjayaen
dc.contributor.authorTsvetkov, Nikolaien
dc.contributor.authorYildiz, Bilgeen
dc.contributor.authorGhoniem, Ahmed F.en
dc.date.accessioned2017-10-04T14:59:16Z-
dc.date.available2017-10-04T14:59:16Z-
dc.date.issued2017-08-24en
dc.identifier.citationZhao Z, Uddi M, Tsvetkov N, Yildiz B, Ghoniem AF (2017) Enhanced intermediate-temperature CO2 splitting using nonstoichiometric ceria and ceria–zirconia. Phys Chem Chem Phys 19: 25774–25785. Available: http://dx.doi.org/10.1039/c7cp04789d.en
dc.identifier.issn1463-9076en
dc.identifier.issn1463-9084en
dc.identifier.doi10.1039/c7cp04789den
dc.identifier.urihttp://hdl.handle.net/10754/625793-
dc.description.abstractCO2 splitting via thermo-chemical or reactive redox has emerged as a novel and promising carbon-neutral energy solution. Its performance depends critically on the properties of the oxygen carriers (OC). Ceria is recognized as one of the most promising OC candidates, because of its fast chemistry, high ionic diffusivity, and large oxygen storage capacity. The fundamental surface ion-incorporation pathways, along with the role of surface defects and the adsorbates remains largely unknown. This study presents a detailed kinetics study of CO2 splitting using CeO2 and Ce0.5Zr0.5O2 (CZO) in the temperature range 600-900℃. Given our interest in fuel-assisted reduction, we limit our study to relatively lower temperatures to avoid excessive sintering and the need for high temperature heat. Compared to what has been reported previously, we observe higher splitting kinetics, resulting from the utilization of fine particles and well-controlled experiments which ensure a surface-limited-process. The peak rates with CZO are 85.9 μmole g–1s–1 at 900℃ and 61.2 μmole g–1s–1 at 700℃, and those of CeO2 are 70.6 μmole g–1s–1 and 28.9 μmole g–1s–1. Kinetics models are developed to describe the ion incorporation dynamics, with consideration of CO2 activation and the charge transfer reactions. CO2 activation energy is found to be – 120 kJ mole-1 for CZO, half of that for CeO2, while CO desorption energetics is analogous among the two samples with the value of ~160 kJ mole-1. The charge-transfer process is found to be the rate-limiting step for CO2 splitting. The evolution of CO32- with surface Ce3+ is examined based on the modeled kinetics. We show that the concentration of CO32- varies with Ce3+ in a linear-flattened-decay pattern, resulting from a mismatch between the kinetics of the two reactions. Our study provides new insights into the significant role of the surface defects and adsorbates in determining the splitting kinetics.en
dc.description.sponsorshipThis study is financially supported by a grant from the British Petroleum (BP) and the King Abdullah University of Science and Technology (KAUST) Investigator Award.en
dc.publisherRoyal Society of Chemistry (RSC)en
dc.titleEnhanced Intermediate-Temperature CO2 Splitting Using Nonstoichiometric Ceria and Ceria-Zirconiaen
dc.typeArticleen
dc.identifier.journalPhys. Chem. Chem. Phys.en
dc.contributor.institutionDepartment of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307, USAen
dc.contributor.institutionDepartment of Mechanical Engineering, University of Alabama, Tuscaloosa, AL 35487, USAen
dc.contributor.institutionDepartment of Nuclear Science & Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307, USAen
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