Cooperative CO$_2$ capture via oxalate formation on metal-decorated graphene

TL;DR

This study uses computational methods to explore how CO₂ interacts with metal-decorated graphene, revealing that certain metals facilitate strong chemisorption and oxalate formation, which could improve CO₂ storage strategies.

Contribution

It provides a detailed molecular-level understanding of CO₂ adsorption and oxalate formation on metal-decorated graphene surfaces using density functional theory.

Findings

Enhanced CO₂ adsorption on decorated graphene surfaces.

Strong chemisorption of CO₂ as oxalate or bent anion on specific metals.

Charge transfer from metal adatoms to CO₂ molecules.

Abstract

CO$_2$ capture using carbon-based materials, particularly graphene and graphene-like materials, is a promising strategy to deal with CO$_2$ emissions. However, significant gaps remain in our understanding of the molecular-level interaction between CO$_2$ molecules and graphene, particularly, in terms of chemical bonding and electron transfer. In this work, we employ random structure search and density functional theory to understand the adsorption of CO$_2$ molecules on Ca, Sr, Na, K, and Ti decorated graphene surfaces. Compared to the pristine material, we observe enhanced CO$_2$ adsorption on the decorated graphene surfaces. Particularly on group 2 metals and titanium decorated graphene, CO$_2$ can be strongly chemisorbed as a bent CO$_2$ anion or as an oxalate, depending on the number of CO$_2$ molecules. Electronic structure analysis reveals the adsorption mechanism to involve an ionic charge transfer from the metal adatom to the adsorbed CO$_2$. Overall, this study suggests that reducing CO$_2$ to oxalate on group 2 metals and titanium metal-decorated graphene surfaces is a potential strategy for CO$_2$ storage.