Georgies, Alene (PhD)Nigussie, Birhanu2021-02-232023-11-282021-02-232023-11-282020-10http://etd.aau.edu.et/handle/12345678/25198Electrochemical carbon dioxide reduction reaction (ECR) on surface CuS (001) is one of the most capable approaches to convert CO2 gases to formic acid and carbon monoxide products. Geometry optimization and Gibbs free energy calculation were carried out using density functional theory with general gradient approximation of Perdew–Burke–Ernzerhof (PBE) as implemented in quantum ESPRESSO and VASP software package with computational hydrogen electrode (CHE) approaches. In this work the bulk CuS, CuS (001) surface and adsorbate configuration structures of intermediate species (*H, *OCHO, *COOH, and *CO) and reduction mechanisms were optimized geometry structure and calculated Gibbs free energy. Herein, the two elementary reaction paths are proposed * + CO2  *OCHO  HCOOH, and * + CO2  *COOH  *CO + H2O CO for the formation of formic acid and carbon monoxide and their activation barrier energy for intermediate *OCHO, *COOH_Cu, *COOH_S, *CO_Cu, and *CO_S are -0.03eV, +0.74 eV, +1.47 eV, -0.32 eV, and -1.05 eV respectively at 0V vs RHE. Intermediate *OCHO and *COOH_Cu have smallest activation barrier energy than the others. This study revealed that easier reaction would be occurred on *OCHO and *COOH_Cu intermediate. So that CuS (001) surface has highly selective catalyst and favourable to the formation of formic acid and good selective to carbon monoxide through *OCHO and *COOH-Cu intermediate, respectively.en-USDensity functional theoryElectrocatalystsElectrochemical reduction of CO2 reactionselectivityThesis