Bamboo-like MnO⋅CoO: High-performance catalysts for the oxidative removal of toluene.

The manganese-cobalt mixed oxide nanorods were fabricated using a hydrothermal method with different metal precursors (KMnO and MnSO·HO for MnO and Co(NO)⋅6HO and CoCl⋅6HO for CoO). Bamboo-like MnO⋅CoO (B-MnO⋅CoO (S)) was derived from repeated hydrothermal treatments with CoO@MnO and MnSO⋅HO, whereas CoO@MnO nanorods were derived from hydrothermal treatment with CoO nanorods and KMnO. The study shows that manganese oxide was tetragonal, while the cobalt oxide was found to be cubic in the crystalline arrangement. Mn surface ions were present in multiple oxidation states (e.g., Mn and Mn) and surface oxygen deficiencies. The content of adsorbed oxygen species and reducibility at low temperature declined in the sequence of B-MnO⋅CoO (S) > CoO@MnO > MnO > CoO, matching the changing trend in activity. Among all the samples, B-MnO⋅CoO (S) showed the preeminent catalytic performance for the oxidation of toluene (T = 187°C, T = 276°C, and T = 339°C). In addition, the B-MnO⋅CoO (S) sample also exhibited good HO-, CO-, and SO-resistant performance. The good catalytic performance of B-MnO⋅CoO (S) is due to the high concentration of adsorbed oxygen species and good reducibility at low temperature. Toluene oxidation over B-MnO⋅CoO (S) proceeds through the adsorption of O and toluene to form O*, OH*, and HC(CH)* species, which then react to produce benzyl alcohol, benzoic acid, and benzaldehyde, ultimately converting to CO and HO. The findings suggest that B-MnO⋅CoO (S) has promising potential for use as an effective catalyst in practical applications.