关键词: 密度泛函理论计算, CO2还原, 反应路径

Abstract: CO2 reduction on Cu(111) single crystal surfaces was studied using DFT calculations on the reaction energies and the minimum energy paths. The results indicated that the possible reaction paths for CO2 reduction on Cu(111) surface are CO2(g) + H* → COOH* → (CO +OH)*, (CO + H)* → CHO*, CHO + H → CH2O* → (CH2 + O)*, CH2* + 2H* → CH4 or 2CH2* → C2H4. On Cu(111) surface, the reaction rate is controlled by steps of CH2O* → (CH2 + O)*, CO2(g) + H* → COOH → (CO +OH)* and (CO + H)* → CHO*. In addition, the reaction energies for various steps in the electrochemical reduction of CO2 were calculated under different electrode potentials. The results indicated that HCOO- and CO are mainly formed when the potential is more positive than -0.50V (vs. RHE). The hydrogenated dissociation of CO2 to form CO and the subsequent hydrogenation of CO become increasingly exothermic as the potential goes negative, so that hydrocarbons gradually becomes the favored products in the electrochemical reduction. Under electrochemical conditions, the CHO intermediate prefers to dissociate to form CH, rather than to form CH2O intermediate via protonation as does in gas phase reduction.

Key words: Density functional theory calculations, Carbon dioxide reduction, The minimum energy paths