Rights statement: This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright ©2017 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/10.1021/acs.jpcc.7b05888
Accepted author manuscript, 2.78 MB, PDF document
Available under license: CC BY-NC: Creative Commons Attribution-NonCommercial 4.0 International License
Final published version
Research output: Contribution to Journal/Magazine › Journal article › peer-review
| <mark>Journal publication date</mark> | 12/10/2017 |
|---|---|
| <mark>Journal</mark> | The Journal of Physical Chemistry C |
| Issue number | 40 |
| Volume | 121 |
| Number of pages | 10 |
| Pages (from-to) | 21877-21886 |
| Publication Status | Published |
| Early online date | 14/09/17 |
| <mark>Original language</mark> | English |
Among the many different processes proposed for large-scale carbon capture and storage (CCS), high temperature CO2 looping has emerged as a favorable candidate due to the low theoretical energy penalties that can be achieved. Many different materials have been proposed for use in such a process, the process requiring fast CO2 absorption reaction kinetics as well as being able to cycle the material for multiple cycles without loss of capacity. Lithium ternary oxide materials, and in particular Li2ZrO3, have displayed promising performance, but further modifications are needed to improve their rate of reaction with CO2. Previous studies have linked rates of lithium ionic conduction-with CO2 absorption in similar materials, and in this work we present work aimed at exploring the effect of aliovalent doping on the efficacy of Li2ZrO3 as a CO2 sorbent. Using a combination of X-ray powder diffraction, theoretical calculations, and solid-state nuclear magnetic resonance, we studied the impact of Nb, Ta, and Y doping on the structure, Li ionic motion, and CO2 absorption properties of Li2ZrO3. These methods allowed us to characterize the theoretical and experimental doping limit into the pure material, suggesting that vacancies formed upon doping are not fully disordered but instead are correlated to the dopant atom positions, limiting the solubility range. Characterization of the lithium motion using variable-temperature solid-state nuclear magnetic resonance confirms that interstitial doping with Y retards the movement of Li ions in the structure, whereas vacancy doping with Nb or Ta results in a similar activation energy as observed for nominally pure Li2ZrO3. However, a marked reduction in the CO2 absorption of the Nb- and Ta-doped samples suggests that doping also leads to a change in the carbonation equilibrium of Li2ZrO3, disfavoring the CO2 absorption at the reaction temperature. This study shows that a complex mixture of structural, kinetic, and dynamic factors can influence the performance of Li-based materials for CCS and underscores the importance of balancing these different factors in order to optimize the process.