Ligand-Mediated Cobalt Oxide Nanocatalysts Unlocking Efficient Toluene Oxidation: Facet Engineering and Morphology Control

Regulating the oxygen vacancy concentration and active sites of Co3O4 through crystal facet engineering and morphological modulation can significantly optimize its catalytic performance. In this study, a ligand-mediated synergistic strategy for crystal facet and morphology regulation was employed to construct Co3O4 catalysts exposing distinct facets, including {001}, {011}, {111}, and {110}, and the catalytic activity of these catalysts was evaluated for the oxidation of toluene. Catalytic tests revealed that Co3O4–S achieved a T90 (temperature for 90% toluene conversion) of 259 °C, with the activity order being dodecahedron Co3O4–S {110} > flower-like Co3O4–H {011} > disciform Co3O4–Y {111} > cube-type Co3O4-L {001}. The superior catalytic activity of Co3O4–S is attributed to its exposed {110} crystal facets, which feature abundant oxygen vacancies, a higher concentration of Co3+ active sites, and a larger specific surface area. Density functional theory (DFT) calculations reveal that the {110} crystal plane of Co3O4–S features the lowest oxygen vacancy formation energy (EVO {110} = 4.41 eV), the optimal O2 adsorption energy (Eads {110} = −1.88 eV), and toluene adsorption energy (Eads {110} = −2.38 eV), indicating strong ability for oxygen activation. This study clarifies the mechanism of the ligand-mediated facet-morphology synergistic regulation strategy, establishes a complete structure–activity chain of “facet/morphology → oxygen vacancy → adsorption energy → catalytic activity” for toluene oxidation, and provides key theoretical support and technical references for the rational design of high-efficiency non-noble metal catalysts for toluene oxidation.