Density Functional Theory plus U Study of Methanol Adsorption and Decomposition on CuO Surfaces with Oxygen Vacancy

The adsorption and decomposition of methanol (CH3OH) and methoxy radical (CH3O) on CuO(111) were investigated via density functional theory calculations with a Hubbard Ucorrection. The configurations and electronic structures of CH3OH and CH3O adsorbed on CuO(111) surfaces were analyzed. CH3OH molecules were preferentially adsorbed on Cu top sites with O-MeOH atoms and H-O-3C bonds formed simultaneously. Adsorption on Cu-3C sites was more stable than on Cu-4C sites, with higher binding energy and shorter Cu-O-MeOH and H-O-CuO bonds. Stable configurations were also achieved with O-MeOH-H bond scission, which were only found on Cu-3C and O-3C sites. On surfaces with oxygen vacancies, adsorption configurations did not change a lot, while there was increased adsorption energy with shorter bond lengths of Cu-O-MeOH and H-O-CuO and longer bond lengths of H-O-MeOH, indicating the formation of oxygen vacancies enhanced the CH3OH adsorption and H-O-MeOH bond scission, and thus accelerated CH3OH decomposition. The dissociative adsorption configuration MeOH-ov3C5 had the highest adsorption energy, at -0.71 eV, with the H-O-CuO bond length at 1.00 angstrom and H-O-MeOH at 1.70 angstrom. Compared with CH3OH, the adsorption energy of CH3O was much higher and reached -1.52 eV in MeO-3C2. The Cu-O-MeO and C-O-MeO bond distances were 1.80 angstrom and 1.40 angstrom, respectively, which were both shorter than CH3OH adsorption. The formation of oxygen vacancies significantly enhanced CH3O adsorption, as CH3O moved to a vacancy and bound with three Cu atoms by O-MeO, whose adsorption energy increased to -3.19 eV. Other configurations had O-MeO binding with two Cu-3C atoms and formed a bridging bond, with adsorption energies of -2.53 and -2.61 eV.

Automated summary

The adsorption and decomposition of methanol and methoxy radical on CuO(111) surfaces were investigated using density functional theory calculations with a Hubbard U correction. The formation of oxygen vacancies significantly enhanced the adsorption of methanol and methoxy radical, and accelerated the decomposition of methanol.