DFT study of CO₂ activation on pristine and vacancy-containing 2D-GeC monolayers

Abstract

Designing a highly reactive adsorbent material for the catalytic conversion of carbon dioxide (CO₂) into valuable products to help ameliorate climate change and address the decreasing availability of fossil fuels is a widely explored application of two-dimensional (2D) nanomaterials. Herein, we present a 2D graphene-like monolayer (ML) of germanium (Ge) and carbon (C) atoms (2D GeC ML) for highly efficient CO₂ adsorption and activation. We have employed first-principles calculations based on the density functional theory (DFT) to investigate the adsorption behavior of CO₂ molecules at pristine GeC MLs and MLs containing defects/vacancies (C-vacancy V_C, Ge-vacancy V_Ge, and combined Ge- and C-vacancies V_Ge/C). We present a detailed description of the nature of the interaction and the mechanism of CO₂ conversion via in-depth projected densities of states, electronic band structures, charge density analysis, and Bader charge transfer analysis. The results show that CO₂ molecule weakly binds with the 2D GeC ML, with an adsorption energy (E_ads) of only −0.13 eV, rendering 2D GeC ML unsuitable for the reduction of CO₂. In contrast, CO₂ gas molecules show strong chemisorption on vacancy-defected GeC MLs with significant Bader charge transfer. The CO₂@GeC_V_Ge ML system displays a maximum E_ads of −4.46 eV, geometrical deformation, and a Bader charge transfer of −1.44 e⁻ to the CO₂ molecule. Thus, V_Ge is the most promising candidate among all considered GeC systems to enable the electrochemical CO₂ reduction reaction.

Keywords

2D GeC / DFT / CO₂ adsorption / Electrocatalysis / Defects

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

CRediT authorship contribution statement

Kamal Kumar: Writing - original draft, Investigation, Validation, Conceptualization, Visualization, Formal analysis. Abhishek Dhasmana: Formal analysis, Investigation. Nora H. de Leeuw: Resources, Software, Writing - review & editing. Jost Adam: Resources, Software, Writing - review & editing. Abhishek K. Mishra: Writing - review & editing, Software, Methodology, Conceptualization, Supervision, Project administration, Funding acquisition, Validation, Resources, Investigation.

Acknowledgements

Prof. Abhishek K. Mishra (AKM) acknowledges the Science and Engineering Research Board (SERB) for a state university research excellence (SURE) grant (SUR/2022/004935). Via our membership of the UK’s HEC Materials Chemistry Consortium, which is funded by EPSRC (EP/X035859), we also acknowledge the use of the ARCHER2 UK National Supercomputing Service (https://www.archer2.ac.uk). This research work was conducted with the financial support, provided by UPES, Dehradun, India.

Supplementary materials

Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.chphma.2025.06.002.

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