Mechanism investigation on the synergistic effect between Fe₅C₂ and Cu in CuFeZn catalysts for the selective hydrogenation of CO₂ to ethanol

As a promising technology, the selective hydrogenation of CO₂ to ethanol using CuFeZn catalysts has attracted significant attention. This study systematically investigates the mechanism of the hydrogenation of CO₂ to ethanol over the CuFeZn model catalyst using periodic density functional theory (DFT), with particular focus on the key steps in CO₂ hydrogenation. The calculations indicate that the formation of the CO* species is crucial for the production of CH₃CH₂OH, which requires overcoming an energy barrier of 1.91 eV. The coupling of CO* with CH₃* is the rate-determining step, which involves overcoming an energy barrier of 2.77 eV. Further analysis shows that the CuFeZn catalyst's synergistic effect significantly influences CO₂ activation and the coupling reaction between CO* and CH₃*, thereby enhancing CH₃CH₂OH formation. The high catalytic performance of the CuFeZn catalyst is attributed to the synergistic interactions between the active Fe₅C₂ and Cu. Density of States (DOS) and Electronic Localization Function (ELF) analyses show that the elevated Cu d-band center and the high electronic localization of Fe_Ⅳ in Fe₅C₂ enhance the formation of CO* species, thus promoting ethanol synthesis. In summary, by utilizing multiple active components to modulate the generation of CO* species and their activation barriers for coupling with CH₃*, the selective production of ethanol can be significantly improved. This study underscores the crucial role of the CuFeZn catalyst for CO₂ hydrogenation to ethanol, providing valuable theoretical insights for future catalyst design and optimization.