Armoring of MgO by a Passivation Layer Impedes Direct Air Capture of CO2

Juliane Weber; Vitalii Starchenko; Ke Yuan; Lawrence M. Anovitz; Anton V. Ievlev; Raymond R. Unocic; Albina Y. Borisevich; Matthew G. Boebinger; Andrew G. Stack

doi:10.1021/acs.est.3c04690

Armoring of MgO by a Passivation Layer Impedes Direct Air Capture of CO₂

Juliane Weber, Vitalii Starchenko, Ke Yuan, Lawrence M. Anovitz, Anton V. Ievlev, Raymond R. Unocic, Albina Y. Borisevich, Matthew G. Boebinger, Andrew G. Stack

Research output: Contribution to journal › Article › peer-review

7 Scopus citations

Abstract

It has been proposed to use magnesium oxide (MgO) to separate carbon dioxide directly from the atmosphere at the gigaton level. We show experimental results on MgO single crystals reacting with the atmosphere for longer (decades) and shorter (days to months) periods with the goal of gauging reaction rates. Here, we find a substantial slowdown of an initially fast reaction as a result of mineral armoring by reaction products (surface passivation). In short-term experiments, we observe fast hydroxylation, carbonation, and formation of amorphous hydrated magnesium carbonate at early stages, leading to the formation of crystalline hydrated Mg carbonates. The preferential location of Mg carbonates along the atomic steps on the crystal surface of MgO indicates the importance of the reactive site density for carbonation kinetics. The analysis of 27-year-old single-crystal MgO samples demonstrates that the thickness of the reacted layer is limited to ∼1.5 μm on average, which is thinner than expected and indicates surface passivation. Thus, if MgO is to be employed for direct air capture of CO₂, surface passivation must be circumvented.

Original language	English
Pages (from-to)	14929-14937
Number of pages	9
Journal	Environmental Science and Technology
Volume	57
Issue number	40
DOIs	https://doi.org/10.1021/acs.est.3c04690
State	Published - Oct 10 2023

Funding

This work was mainly supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division. A minor part of this research (ToF-SIMS characterization and preliminary TEM characterization) was funded by an ORNL Internal Laboratory Directed Research & Development (LDRD) project. AFM-ToF-SIMS and TEM characterization were conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility at ORNL and using instrumentation within ORNL’s Materials Characterization Core provided by UT-Battelle, LLC under Contract DE-AC05-00OR22725 with the U.S. Department of Energy. The authors thank James Kolopus for providing the MgO samples used in this study. Andrew Miskowiec is acknowledged for access to the Raman instrument. This manuscript has been co-authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so for U.S. government purposes. The U.S. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). This work was mainly supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division. A minor part of this research (ToF-SIMS characterization and preliminary TEM characterization) was funded by an ORNL Internal Laboratory Directed Research & Development (LDRD) project. AFM–ToF-SIMS and TEM characterization were conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility at ORNL and using instrumentation within ORNL’s Materials Characterization Core provided by UT-Battelle, LLC under Contract DE-AC05-00OR22725 with the U.S. Department of Energy. The authors thank James Kolopus for providing the MgO samples used in this study. Andrew Miskowiec is acknowledged for access to the Raman instrument. This manuscript has been co-authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so for U.S. government purposes. The U.S. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).

Funders	Funder number
DOE Public Access Plan
ORNL Laboratory Research and Development Program
U.S. Government
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Oak Ridge National Laboratory	DE-AC05-00OR22725
Laboratory Directed Research and Development
Division of Materials Sciences and Engineering

Keywords

MgO
carbon capture
decarbonization
direct air capture
separation

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1021/acs.est.3c04690

Cite this

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abstract = "It has been proposed to use magnesium oxide (MgO) to separate carbon dioxide directly from the atmosphere at the gigaton level. We show experimental results on MgO single crystals reacting with the atmosphere for longer (decades) and shorter (days to months) periods with the goal of gauging reaction rates. Here, we find a substantial slowdown of an initially fast reaction as a result of mineral armoring by reaction products (surface passivation). In short-term experiments, we observe fast hydroxylation, carbonation, and formation of amorphous hydrated magnesium carbonate at early stages, leading to the formation of crystalline hydrated Mg carbonates. The preferential location of Mg carbonates along the atomic steps on the crystal surface of MgO indicates the importance of the reactive site density for carbonation kinetics. The analysis of 27-year-old single-crystal MgO samples demonstrates that the thickness of the reacted layer is limited to ∼1.5 μm on average, which is thinner than expected and indicates surface passivation. Thus, if MgO is to be employed for direct air capture of CO2, surface passivation must be circumvented.",

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AB - It has been proposed to use magnesium oxide (MgO) to separate carbon dioxide directly from the atmosphere at the gigaton level. We show experimental results on MgO single crystals reacting with the atmosphere for longer (decades) and shorter (days to months) periods with the goal of gauging reaction rates. Here, we find a substantial slowdown of an initially fast reaction as a result of mineral armoring by reaction products (surface passivation). In short-term experiments, we observe fast hydroxylation, carbonation, and formation of amorphous hydrated magnesium carbonate at early stages, leading to the formation of crystalline hydrated Mg carbonates. The preferential location of Mg carbonates along the atomic steps on the crystal surface of MgO indicates the importance of the reactive site density for carbonation kinetics. The analysis of 27-year-old single-crystal MgO samples demonstrates that the thickness of the reacted layer is limited to ∼1.5 μm on average, which is thinner than expected and indicates surface passivation. Thus, if MgO is to be employed for direct air capture of CO2, surface passivation must be circumvented.

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