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

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.

SUBMITTER: Weber J

PROVIDER: S-EPMC10569045 | biostudies-literature | 2023 Oct

REPOSITORIES: biostudies-literature

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Armoring of MgO by a Passivation Layer Impedes Direct Air Capture of CO<sub>2</sub>.

Weber Juliane J Starchenko Vitalii V Yuan Ke K Anovitz Lawrence M LM Ievlev Anton V AV Unocic Raymond R RR Borisevich Albina Y AY Boebinger Matthew G MG Stack Andrew G AG

Environmental science & technology 20230922 40

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 hydrox ...[more]

PMID: 37737106

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

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Armoring of MgO by a Passivation Layer Impedes Direct Air Capture of CO<sub>2</sub>.

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

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Armoring of MgO by a Passivation Layer Impedes Direct Air Capture of CO<sub>2</sub>.

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OmicsDI is part of the ELIXIR infrastructure

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