Effect of surface oxygen vacancy sites on ethanol synthesis from acetic acid hydrogenation on a defective In₂O₃(110) surface

Abstract

Developing a new type of low-cost and high-efficiency non-noble metal catalyst is beneficial for industrially massive synthesis of alcohols from carboxylic acids which can be obtained from renewable biomass. In this work, the effect of active oxygen vacancies on ethanol synthesis from acetic acid hydrogenation over defective In₂O₃(110) surfaces has been studied using periodic density functional theory (DFT) calculations. The relative stabilities of six surface oxygen vacancies from O_v1 to O_v6 on the In₂O₃(110) surface were compared. D1 and D4 surfaces with respective O_v1 and O_v4 oxygen vacancies were chosen to map out the reaction paths from acetic acid to ethanol. A reaction cycle mechanism between the perfect and defective states of the In₂O₃ surface was found to catalyze the formation of ethanol from acetic acid hydrogenation. By H₂ reduction the oxygen vacancies on the In₂O₃ surface play key roles in promoting CH₃COO* hydrogenation and C-O bond breaking in acetic acid hydrogenation. The acetic acid, in turn, benefits the creation of oxygen vacancies, while the C-O bond breaking of acetic acid refills the oxygen vacancy and, thereby, sustains the catalytic cycle. The In₂O₃ based catalysts were shown to be advantageous over traditional noble metal catalysts in this paper by theoretical analysis.