Efficient search for acetic acid synthesis pathway based on the bond disconnection process on Rh surface and Rh/metal oxide interface

Abstract

The interfacial structure between Rh and the metal oxide support (or promoter) is thought to play an essential role in the synthesis of C2-oxygenated compounds such as acetic acid (CH3COOH). However, due to the complexity of the interface structure, the CH3COOH synthesis pathway has yet to be explored theoretically at the metal/metal oxide interface. In this study, we examined the CH3COOH synthesis pathway at the Rh surface and Rh/metal oxide interface based on the systematic investigation of bond disconnection of the CH3COOH molecule. First, CH3COOH synthesis pathways that include small activation energy Ea(c) were explored on the Rh(111) and it was shown that the reaction pathways CH + CO(H) → CHCO(H) → CH2CO(H) → CH3COH → CH3COOH were found [the rate-limiting step (RLS) is the C=O bond connection with Ea(c) = 1.41 eV]. After that, the CH3COOH synthesis pathway at the Rh/ZrO2 interface was investigated, and it was found that the CH3COOH synthesis pathway via the acetyl (CH3CO) generated from Rh–CH3 and Rh–CO with an oxygen atom in Rh–CO interacted with Zr cation (the RLS was the C–C bond connection with Ea(c) = 0.73 eV). This study provides guidelines for the design of a rational active metal/metal oxide interface for C2 oxygenates synthesis.