Metal-modified CeO2 nanobelts for catalytic oxidation of ethyl acetate: Roles of surface lattice oxygen and hydrolysis behaviors

Based on the comparison of three counterparts [Mg-, Al- and Cu-modified CeO2 nanobelts], it is illustrated that the low-temperature hydrolysis of ethyl acetate (EA) rapidly occurs and the removal of absorbed hydrolyzates (mainly acetates) is considered the rate-determining step. As the temperature increases, the escape of surface lattice oxygen (Os-latt) breaks through the shield of hydrolyzates and promotes the deep oxidation of intermediate products. Additionally, the activated Os-latt also facilitates the C-O bond cleavage in EA by nucleophilic attack. Due to the Os-latt escape, surface metal ions achieve more unsaturated coordinations to absorb the CH3COO– species, leading to competitive adsorption between O2 and hydrolyzates. The Cu modification strengthens the coordination adsorption of CH3COO– species, and the Al modification exhibits a low Os-latt mobility. These factors all contribute to a strong adsorption or accumulation of surface hydrolyzates. Therefore, a favorable ester hydrolysis-oxidation process over CeO2-based catalysts depends not only on excellent Os-latt mobility but also the suitable adsorption capacity of hydrolyzates, such as Mg modification.