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 <i>T</i>₉₀ (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 (<i>E</i>_VO {110} = 4.41 eV), the optimal O₂ adsorption energy (<i>E</i>_ads {110} = -1.88 eV), and toluene adsorption energy (<i>E</i>_ads {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.