Optimized methane combustion behavior by engineering dual oxygen defect structures between Co3O4 and MOF-derived Ce1-xLaxO2-δ solid solution

Abstract

Herein, Co3O4/Ce1-xLaxO2-δ nanocatalysts were established for methane combustion, integrating the sacrificial MOF-template method and deposition-precipitation technique. A favored La-insertion into CeO2 matrix created smaller-sized Ce1-xLaxO2-δ sosoloid with more defective structure due to the enhanced transformation of Ce4+ to Ce3+, helping in the intimate contact with Co3O4. This lessened the particle sizes of Co3O4 and alleviated the hybridization strength of Co3+ 3d and O 2p orbitals, which optimized the mobility of surface lattice oxygen and reducibility of Co3O4, and enriched Co3+ species to attack C–H bonds. Moreover, the transmission of gaseous oxygen and/or activated oxygen of Ce1-xLaxO2-δ to Co3O4 was expedited, availing the compensation of oxygen vacancies on reduced Co3O4 to regain dissociation centers for methane. Expectedly, the combined function of Co3+/Co2+, Ce4+/Ce3+ and O/OV redox couples allowed Co3O4/Ce0.6La0.4O2-δ with preferable methane removal efficiency to its counterparts, accompanied with desirable recyclability and long-term stability.