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

Regulating the oxygen vacancy concentration and active sites of Co 3 O 4 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 Co 3 O 4 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 Co 3 O 4 –S achieved a T 90 (temperature for 90% toluene conversion) of 259 °C, with the activity order being dodecahedron Co 3 O 4 –S {110} > flower-like Co 3 O 4 –H {011} > disciform Co 3 O 4 –Y {111} > cube-type Co 3 O 4 -L {001}. The superior catalytic activity of Co 3 O 4 –S is attributed to its exposed {110} crystal facets, which feature abundant oxygen vacancies, a higher concentration of Co 3+ active sites, and a larger specific surface area. Density functional theory (DFT) calculations reveal that the {110} crystal plane of Co 3 O 4 –S features the lowest oxygen vacancy formation energy ( E VO {110} = 4.41 eV), the optimal O 2 adsorption energy ( E ads {110} = −1.88 eV), and toluene adsorption energy ( E 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.