Highly surface-active Ca(OH)$_2$ monolayer as a CO$_2$ capture material

TL;DR

This paper introduces portlandene, a stable, defect-engineered monolayer material derived from bulk portlandite, which effectively captures CO$_2$ and can be regenerated with mild electric fields, offering a promising solution for greenhouse gas mitigation.

Contribution

The study demonstrates the creation of a stable, highly CO$_2$-adsorbing monolayer material with defect engineering and reveals its efficient, reversible capture mechanism using electric fields, unlike traditional methods.

Findings

Portlandene is a stable monolayer derived from bulk portlandite.

Defect engineering enhances the chemical activity of portlandene.

Portlandene can selectively capture CO$_2$ and release it with mild electric fields.

Abstract

Greenhouse gas emissions originating from fossil fuel combustion contribute significantly to global warming, and therefore the design of novel materials that efficiently capture CO$_2$ can play a crucial role in solving this challenge. Here, we show that reducing the dimensionality of bulk crystalline portlandite results in a stable monolayer material, named portlandene, that is highly effective at capturing CO$_2$. Based on theoretical analysis comprised of ab-initio quantum mechanical calculations and force-field molecular dynamics simulations, we show that this single-layer phase is robust and maintains its stability even at high temperatures. The chemical activity of portlandene is seen to further increase upon defect engineering of its surface using vacancy sites. Defect-containing portlandene is capable of separating CO and CO$_2$ from a syngas (CO/CO$_2$/H$_2$) stream, yet is inert to water vapor. This selective behavior and the associated mechanisms have been elucidated by examining the electronic structure, local charge distribution and bonding orbitals of portlandene. Additionally, unlike conventional CO$_2$ capturing technologies, the regeneration process of portlandene does not require high temperature heat treatment since it can release the captured CO$_2$ by application of a mild external electric field, making portlandene an ideal CO$_2$ capturing material for both pre- and post-combustion processes.