Computational Design of Electro-Organocatalysts and Transition Metal Sulfides for the Electrochemical Reduction of CO2

Author

Foroogh KhezeliFollow

Degree

Doctor of Philosophy (PhD)

Department

Chemical Engineering

Document Type

Dissertation

Abstract

Abstract

Electrochemical CO₂ reduction (ECO₂RR) has emerged as a promising approach for generating carbon-neutral liquid fuels by utilizing excess renewable electricity to convert CO₂. This thesis aims to employ atomistic simulations by using Density Functional Theory (DFT) to investigate the mechanistic details of how transition metal sulfides and electro-organocatalysts can enhance the activity and selectivity towards desired products, including those containing C-H bonds and molecules with C-C bonds. For this project, three different electrocatalysts were designed computationally.

Firstly, MoS₂ was chosen as a transition metal sulfide catalyst with the objective of understanding the kinetics involved in the reduction of CO₂ to CO at a low overpotential of -0.5 V vs. RHE and pH of 4. The aim was to identify the rate-limiting step with an energy barrier as low as 0.74 eV. Secondly, 1,3-dimethyl-4-imidazoline electro-organocatalyst was utilized to explore CO₂ reduction beyond CO production. Under specific conditions of pH 7.85, an electrode potential of -0.85 V vs. RHE, and a temperature of 80 ℃, this organomolecule demonstrated the capability of reducing CO₂ to formaldehyde. The reaction proceeded through a series of steps, including CO₂ activation, Proton-Coupled Electron Transfer (PCET), Tautomerization, dehydration, and elimination, ultimately resulting in the formation of products with C-H bonds.

The same electro-organocatalyst, 1,3-dimethyl-4-imidazoline, was investigated for its potential to form long-chain aldehydes through reductive aldol condensation. This process involved the incremental growth of an alkyl chain by one carbon atom at a time. By performing reductive addition of formaldehyde to a second aldehyde, an extended product aldehyde was generated. Under specific conditions of an electrode potential of -0.88 V vs. RHE, a formaldehyde

concentration of 8.71×10^-3 mol/L (log[CH₂O]=-2.06), and a pH of 6.63, this molecule successfully reduced CO₂ to acetaldehyde.

Date

7-11-2023

Recommended Citation

Khezeli, Foroogh, "Computational Design of Electro-Organocatalysts and Transition Metal Sulfides for the Electrochemical Reduction of CO2" (2023). LSU Doctoral Dissertations. 6240.
https://repository.lsu.edu/gradschool_dissertations/6240

Committee Chair

Plaisance, Craig