Tuning oxygen vacancies in cu, Mn, Ni-substituted Co3O4 spinel catalysts for enhanced catalytic oxidation of toluene

Developing transition metal oxide-based catalysts with both high thermal stability and catalytic activity for the effective volatile organic compounds (VOCs) removal remains a major challenge in heterogeneous catalysis. In this work, a series of Cu, Mn, Co and Ni substituted Co 3 O 4 spinel catalysts with a large number of oxygen vacancies were produced as extremely stable and active substances for the oxidation of toluene. The CuCo 2 O 4 catalyst, prepared through transition metal substitution, demonstrated exceptional performance with T 50 , T 90 , and complete conversion temperatures of 204 °C, 220 °C, and 228 °C, respectively. Furthermore, the CuCo 2 O 4 catalyst displayed markedly enhanced thermal stability compared to other catalysts, which was crucial for practical implementation. Its superior catalytic activity originated from electron transfer between Co and Cu cations, facilitated by lattice oxygen, which increased the Co 3+ /Co 2+ ratio. This structural modification strengthened oxygen migration and reducibility within the spinel framework, facilitating efficient regeneration of lattice oxygen and rapid activation of adsorbed oxygen species. Kinetic analyses corroborated these findings, revealing that CuCo 2 O 4 possessed the lowest activation energy ( E a  = 40.40 kJ/mol), thereby reducing the energy barrier for toluene oxidation. These results demonstrate that the CuCo 2 O 4 catalyst represents a promising candidate for practical applications, combining high catalytic activity for toluene oxidation with exceptional operational durability and thermal stability.