Study on the CO2 activation pathways over MxOy/Cu inverse catalysts

This work systematically investigates the role of inverse oxide-metal interfaces in regulating CO 2 activation during hydrogenation to methanol on Cu(111) surfaces, using density functional theory (DFT) calculations. Three representative inverse catalysts, Ce 4 O 8 /Cu(111), Mg 4 O 4 /Cu(111), and Zn 6 O 6 /Cu(111), were constructed to elucidate the effects of oxide clusters on interfacial electronic structure, CO 2 adsorption, and activation pathways. The results demonstrate that: (1) The introduction of oxide clusters significantly modulates the local geometric structure and electronic properties of the Cu(111) surface, thereby affecting CO 2 adsorption and activation. Among the systems studied, Ce 4 O 8 /Cu(111) exhibits the strongest adsorption capability (E ads = −0.623 eV), accompanied by pronounced molecular bending, indicating a high degree of activation. Moreover, both physical adsorption and chemical adsorption of CO 2 are observed at the Ce 4 O 8 /Cu(111) and Zn 6 O 6 /Cu(111) interfaces, while Mg 4 O 4 /Cu(111) mainly exhibits physical adsorption. (2) Among the investigated initial CO 2 activation pathways, the HCOO pathway exhibits the lowest energy barrier for all three systems, although their relative activation capabilities are different. (3) Charge density difference and charge population analyses reveal significant electron transfer induced by the oxide-metal interfaces, with Ce 4 O 8 /Cu(111) exhibiting the strongest interfacial electronic coupling, facilitating CO 2 activation. (4) The calculated reaction energetics indicate that Ce 4 O 8 /Cu(111) exhibits the most favorable CO 2 activation behavior among the three inverse catalyst systems, owing to its lower energy barriers and stronger interfacial electronic coupling. This work reveals, at the atomic scale, the critical role of inverse oxide-metal interfaces in regulating CO 2 activation behavior and provides theoretical insights into the interfacial mechanisms governing CO 2 activation in Cu-based inverse catalysts. The conclusions of this work are limited to the initial CO 2 activation stage and do not represent the overall catalytic performance for methanol synthesis.