The synergistic effects of Cu clusters and In₂O₃ on ethanol synthesis from acetic acid hydrogenation

Abstract

The development of high efficiency catalysts for acetic acid hydrogenation to ethanol could ameliorate the petroleum crisis and acetic acid overproduction. Cu and In₂O₃ catalysts both show catalytic activity for acetic acid hydrogenation. However, monometallic Cu catalysts are less active in the dissociative adsorption of acetic acid through C-O bond breaking, while the H₂ adsorption and dissociation ability of In₂O₃ is weak. In this work, Cu₄/In₂O₃ is designed to enhance the dissociation of both acetic acid and H₂. The detailed mechanism of acetic acid hydrogenation to ethanol on Cu₄/In₂O₃ is explored using periodic density functional theory (DFT). The results show that the H₂ adsorption and dissociation are enhanced by the Cu cluster, while the H atom spillover from Cu to In₂O₃ is favorable on the Cu₄/In₂O₃(110) surface. Additionally, a synergistic effect exists between the Cu cluster and In₂O₃ surface: H₂ adsorbs on the Cu cluster and the dissociated H atoms react with acetic acid activated by the In₂O₃ oxygen vacancy. Finally, compared with a Cu₂In(100) surface, the Cu₄/In₂O₃(110) surface possesses higher catalytic activity owing to the reduced energy barriers of acetic acid dissociation and hydrogenation of the intermediates (CH₃COO*, CH₃CHO*, and CH₃CH₂O*). The Cu₄/In₂O₃ catalyst proposed in this work can provide promising guidance for related catalyst design.