Rich Oxygen Vacancies in Bimetallic MnCo2O4.5 Spheres for Enhancing Lean Methane Catalytic Oxidation.

Methane is the second most prevalent greenhouse gas after carbon dioxide in global climate change, and catalytic oxidation technology is a very effective way to eliminate methane. However, the high reaction temperature of methane catalytic oxidation is an urgent problem that needs to be solved. In this work, a series of MnCo2O4.5 catalysts were prepared using carbon spheres as templates, combined with metal ion adsorption and calcination processes. Excitingly, the catalytic oxidation activity of MnCo2O4.5 spherical catalyst with irregular nanoparticles on the surface for lean methane (T90 = 395 °C) is higher than that of pure phase Co3O4 (T90 = 538 °C) and Mo3O4 (T90 = 581 °C) spherical catalysts and even surpasses most precious metal catalysts. The main reasons are as follows: (1) The spherical core with irregular nanoparticle morphology significantly increases the specific surface area, creating abundant active sites; (2) through the optimized distribution of oxygen vacancies, rapid oxygen migration through this structure can quickly enter the catalytic zone; (3) the hierarchical wall structure expands the interface and provides spatial accommodation for the catalytic process. Meanwhile, the structure of the ball wall further expands the reaction interface, providing sufficient space for the occurrence of reactions. Rich and highly active oxygen vacancies are evenly distributed on the surface and inside of the ball. The extraordinary performance of low-temperature methane combustion catalysts has opened a promising new path, which is expected to inject strong impetus into the global energy transition and environmental protection.