Morphology dependence of Nb2O5-supported cobalt oxide in catalytic toluene oxidation†

Abstract

This research describes the preparation of cobalt-based catalysts supported on Nb₂O₅ substrates of various forms: rods (Nb₂O₅-R), grids (Nb₂O₅-G), and spherical structures (Nb₂O₅-S). These catalysts demonstrated diverse reactivity in toluene oxidation, which correlated with their individual physical and chemical traits and the interfacial interaction between cobalt oxide and the Nb₂O₅ support. Notably, the catalyst with a spherical Nb₂O₅ support (CoO_x/Nb₂O₅-S) outperformed the catalysts with other supports and showed the best activity in oxidizing toluene. The investigation underscored the role of the unique features of the Nb₂O₅ substrate in augmenting the catalyst's efficacy in toluene adsorption and activation. Density functional theory (DFT) revealed more facile toluene adsorption on CoO_x/Nb₂O₅-S (−0.65 eV) and reduced energy requirements for oxygen vacancy creation and adsorption. This suggested that the CoO_x/Nb₂O₅-S catalyst enhanced surface oxygen mobility and boosted catalytic efficiency.