Jump to main content
Jump to site search

Issue 37, 2017
Previous Article Next Article

Enhanced intermediate-temperature CO2 splitting using nonstoichiometric ceria and ceria–zirconia

Author affiliations

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 remain 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 °C. 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−1 s−1 at 900 °C and 61.2 μmole g−1 s−1 at 700 °C, and those of CeO2 are 70.6 μmole g−1 s−1 and 28.9 μmole g−1 s−1. Kinetic 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 between the two samples with a 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 surface defects and adsorbates in determining the splitting kinetics.

Graphical abstract: Enhanced intermediate-temperature CO2 splitting using nonstoichiometric ceria and ceria–zirconia

Back to tab navigation

Supplementary files

Publication details

The article was received on 16 Jul 2017, accepted on 24 Aug 2017 and first published on 24 Aug 2017


Article type: Paper
DOI: 10.1039/C7CP04789D
Citation: Phys. Chem. Chem. Phys., 2017,19, 25774-25785
  •   Request permissions

    Enhanced intermediate-temperature CO2 splitting using nonstoichiometric ceria and ceria–zirconia

    Z. Zhao, M. Uddi, N. Tsvetkov, B. Yildiz and A. F. Ghoniem, Phys. Chem. Chem. Phys., 2017, 19, 25774
    DOI: 10.1039/C7CP04789D

Search articles by author

Spotlight

Advertisements