Model structures of molten salt-promoted MgO to probe the mechanism of MgCO<sub>3</sub> formation during CO<sub>2</sub> capture at a solid–liquid interface

Bork, Alexander H.; Ackerl, Norbert; Reuteler, Joakim; Jog, Sachin Hemant; Gut, David; Zboray, Robert; Müller, Christoph R.

doi:10.1039/d2ta02897b

Cited by 13 publications

(4 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Experimental evidence of the nucleation and growth of MgCO 3 at the liquid−solid interfaces has been recently provided by Xray-and electron microscopy-based techniques, revealing that the nucleation sites are located at the buried MgO/NaNO 3 interface. 27,28 Furthermore, Bork et al observed the presence of etching pits on the surface of a carbonated MgO single crystal in the proximity of MgCO 3 , providing evidence that MgCO 3 forms via a dissolution−recrystallization mechanism. 27 To develop further MgO-based sorbents for CO 2 capture, it is critical to elucidate the key intermediate steps in the carbonation reaction of alkali metal nitrate-promoted MgO.…”

Section: ■ Introductionmentioning

confidence: 99%

“…In the reaction scheme proposed by Harada et al, the formation of MgCO 3 takes place at the MgO/NaNO 3 interface. Experimental evidence of the nucleation and growth of MgCO 3 at the liquid–solid interfaces has been recently provided by X-ray- and electron microscopy-based techniques, revealing that the nucleation sites are located at the buried MgO/NaNO 3 interface. , Furthermore, Bork et al observed the presence of etching pits on the surface of a carbonated MgO single crystal in the proximity of MgCO 3 , providing evidence that MgCO 3 forms via a dissolution–recrystallization mechanism …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Uncovering the CO₂ Capture Mechanism of NaNO₃-Promoted MgO by ¹⁸O Isotope Labeling

Landuyt

Kumar

Yuwono

et al. 2022

JACS Au

Self Cite

View full text Add to dashboard Cite

MgO-based CO2 sorbents promoted with molten alkali metal nitrates (e.g., NaNO3) have emerged as promising materials for CO2 capture and storage technologies due to their low cost and high theoretical CO2 uptake capacities. Yet, the mechanism by which molten alkali metal nitrates promote the carbonation of MgO (CO2 capture reaction) remains debated and poorly understood. Here, we utilize 18O isotope labeling experiments to provide new insights into the carbonation mechanism of NaNO3-promoted MgO sorbents, a system in which the promoter is molten under operation conditions and hence inherently challenging to characterize. To conduct the 18O isotope labeling experiments, we report a facile and large-scale synthesis procedure to obtain labeled MgO with a high 18O isotope content. We use Raman spectroscopy and in situ thermogravimetric analysis in combination with mass spectrometry to track the 18O label in the solid (MgCO3), molten (NaNO3), and gas (CO2) phases during the CO2 capture (carbonation) and regeneration (decarbonation) reactions. We discovered a rapid oxygen exchange between CO2 and MgO through the reversible formation of surface carbonates, independent of the presence of the promoter NaNO3. On the other hand, no oxygen exchange was observed between NaNO3 and CO2 or NaNO3 and MgO. Combining the results of the 18O labeling experiments, with insights gained from atomistic calculations, we propose a carbonation mechanism that, in the first stage, proceeds through a fast, surface-limited carbonation of MgO. These surface carbonates are subsequently dissolved as [Mg2+···CO3 2–] ionic pairs in the molten NaNO3 promoter. Upon reaching the solubility limit, MgCO3 crystallizes at the MgO/NaNO3 interface.

show abstract

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Uncovering the CO₂ Capture Mechanism of NaNO₃-Promoted MgO by ¹⁸O Isotope Labeling

Landuyt

Kumar

Yuwono

et al. 2022

JACS Au

Self Cite

View full text Add to dashboard Cite

show abstract

“…The mechanism through which molten alkali nitrates (or mixtures thereof ) promote the carbonation of MgO is currently debated and intensively studied through both experimental and theoretical approaches (12,(20)(21)(22)(23)(24)(25). For example, it has been proposed by Zhang et al (12) that MgO is partially dissolved in the molten salt, yielding [Mg 2+ …O 2− ] ionic pairs that react with CO 2 , generating in turn [Mg 2+ …CO 3…”

Section: Introductionmentioning

confidence: 99%

Deciphering the structural dynamics in molten salt–promoted MgO-based CO ₂ sorbents and their role in the CO ₂ uptake

Rekhtina

Krödel

et al. 2023

Sci. Adv.

Self Cite

View full text Add to dashboard Cite

The development of effective CO 2 sorbents is vital to achieving net-zero CO 2 emission targets. MgO promoted with molten salts is an emerging class of CO 2 sorbents. However, the structural features that govern their performance remain elusive. Using in situ time-resolved powder x-ray diffraction, we follow the structural dynamics of a model NaNO 3 -promoted, MgO-based CO 2 sorbent. During the first few cycles of CO 2 capture and release, the sorbent deactivates owing to an increase in the sizes of the MgO crystallites, reducing in turn the abundance of available nucleation points, i.e., MgO surface defects, for MgCO 3 growth. After the third cycle, the sorbent shows a continuous reactivation, which is linked to the in situ formation of Na 2 Mg(CO 3 ) 2 crystallites that act effectively as seeds for MgCO 3 nucleation and growth. Na 2 Mg(CO 3 ) 2 forms due to the partial decomposition of NaNO 3 during regeneration at T ≥ 450°C followed by carbonation in CO 2 .

show abstract

“…There have been a series of studies that have explored the role and functioning of promoters on the CO 2 uptake of MgO-based CO 2 absorbents. ,− It has been proposed that MgO dissolves in the molten AMS promoter as [Mg 2+ ···O 2– ] ionic pairs. − , Zhang et al hypothesized that CO 2 is adsorbed at the triple phase boundary (TPB) between solid MgO, liquid AMS, and gaseous CO 2 . The adsorbed CO 2 then reacts with [Mg 2+ ···O 2– ] ionic pairs to form [Mg 2+ ···CO 3 2– ] ionic pairs at the TPB .…”

Section: Introductionmentioning

confidence: 99%

Probing the Local Structure of Na in NaNO₃-Promoted, MgO-Based CO₂ Sorbents via X-ray Absorption Spectroscopy

Rekhtina,

Bugaev,

Dunstan

et al. 2023

Chem. Mater.

Self Cite

View full text Add to dashboard Cite

This work provides insight into the local structure of Na in MgO-based CO 2 sorbents that are promoted with NaNO 3 . To this end, we use X-ray absorption spectroscopy (XAS) at the Na K-edge to interrogate the local structure of Na during the CO 2 capture (MgO + CO 2 ↔ MgCO 3 ). The analysis of Na K-edge XAS data shows that the local environment of Na is altered upon MgO carbonation when compared to that of NaNO 3 in the as-prepared sorbent. We attribute the changes observed in the carbonated sorbent to an alteration in the local structure of Na at the NaNO 3 /MgCO 3 interfaces and/or in the vicinity of [Mg 2+ ···CO 3 2– ] ionic pairs that are trapped in the cooled NaNO 3 melt. The changes observed are reversible, i.e., the local environment of NaNO 3 was restored after a regeneration treatment to decompose MgCO 3 to MgO. The ex situ Na K-edge XAS experiments were complemented by ex situ magic-angle spinning 23 Na nuclear magnetic resonance (MAS 23 Na NMR), Mg K-edge XAS and X-ray powder diffraction (XRD). These additional experiments support our interpretation of the Na K-edge XAS data. Furthermore, we develop in situ Na (and Mg) K-edge XAS experiments during the carbonation of the sorbent (NaNO 3 is molten under the conditions of the in situ experiments). These in situ Na K-edge XANES spectra of molten NaNO 3 open new opportunities to investigate the atomic scale structure of CO 2 sorbents modified with Na-based molten salts by using XAS.

show abstract

Model structures of molten salt-promoted MgO to probe the mechanism of MgCO₃ formation during CO₂ capture at a solid–liquid interface

Abstract: MgO is a promising solid oxide-based sorbent to capture anthropogenic CO2 emissions due to its high theoretical gravimetric CO2 uptake and its abundance. When MgO is coated with alkali metal...

Cited by 13 publications

References 34 publications

Uncovering the CO₂ Capture Mechanism of NaNO₃-Promoted MgO by ¹⁸O Isotope Labeling

Uncovering the CO₂ Capture Mechanism of NaNO₃-Promoted MgO by ¹⁸O Isotope Labeling

Deciphering the structural dynamics in molten salt–promoted MgO-based CO ₂ sorbents and their role in the CO ₂ uptake

Probing the Local Structure of Na in NaNO₃-Promoted, MgO-Based CO₂ Sorbents via X-ray Absorption Spectroscopy

Contact Info

Product

Resources

About

Model structures of molten salt-promoted MgO to probe the mechanism of MgCO3 formation during CO2 capture at a solid–liquid interface

Abstract: MgO is a promising solid oxide-based sorbent to capture anthropogenic CO2 emissions due to its high theoretical gravimetric CO2 uptake and its abundance. When MgO is coated with alkali metal...

Cited by 13 publications

References 34 publications

Uncovering the CO2 Capture Mechanism of NaNO3-Promoted MgO by 18O Isotope Labeling

Uncovering the CO2 Capture Mechanism of NaNO3-Promoted MgO by 18O Isotope Labeling

Deciphering the structural dynamics in molten salt–promoted MgO-based CO 2 sorbents and their role in the CO 2 uptake

Probing the Local Structure of Na in NaNO3-Promoted, MgO-Based CO2 Sorbents via X-ray Absorption Spectroscopy

Contact Info

Product

Resources

About

Model structures of molten salt-promoted MgO to probe the mechanism of MgCO₃ formation during CO₂ capture at a solid–liquid interface

Uncovering the CO₂ Capture Mechanism of NaNO₃-Promoted MgO by ¹⁸O Isotope Labeling

Uncovering the CO₂ Capture Mechanism of NaNO₃-Promoted MgO by ¹⁸O Isotope Labeling

Deciphering the structural dynamics in molten salt–promoted MgO-based CO ₂ sorbents and their role in the CO ₂ uptake

Probing the Local Structure of Na in NaNO₃-Promoted, MgO-Based CO₂ Sorbents via X-ray Absorption Spectroscopy