Interfacial Engineering of High-Entropy Oxides (FeCoNiCrMn)3O4@N-Doped Carbon for Boosting Aerobic C−H Bond Oxidation of Toluene

The selective C−H bond oxidation of toluene to benzaldehyde using molecular O2 with non-noble metal catalysts is challenging but desirable. Herein, a series of high-entropy oxides (FeCoNiCrMn)3O4 supported on mesoporous N-doped carbon was fabricated via a reverse impregnation and calcination method (denoted as HEOs@NC). It was found that high-entropy oxides (FeCoNiCrMn)3O4 nanoparticles were distributed well onto the surface of N-doped carbon, and a distinct interface between them was observed, contributing to the formation of metal-support electronic interaction. XPS and Bader charge results verified that an electron was transferred from (FeCoNiCrMn)3O4 to N-doped carbon. Under the optimized reaction conditions, 12.2% of toluene conversion and 2.0 ×10−4 mmol mg−1cat. h−1 of benzaldehyde formation rate could be obtained with 1.5HEOs@NC catalyst. Moreover, DFT calculations revealed that the supported (FeCoNiCrMn)3O4 displayed stronger adsorption ability toward N-hydroxyphthalimide, and the formation of *PhCH2OH was determined as the rate-determining step. A lower energy barrier was achieved over the supported HEOs owing to the interfacial interaction between (FeCoNiCrMn)3O4 and N-doped carbon. This work developed a supported high-entropy oxides catalyst by rational design of interfacial engineering for the aerobic C−H bond oxidation of toluene.