Properties and Applications of Maze-Like Macroporous Mn<sub>3</sub>O<sub>4</sub> Microspheres Synthesized by Heating in Water Vapor

The thermal decomposition of inorganic salts, including carbonates and oxalates, produces porous oxides while maintaining the particle shape. However, the formed pore size is limited to nanopores smaller than 50 nm. This paper shows that Mn3O4 microspheres consisting of open macropores exceeding 50 nm can be synthesized through the thermal decomposition of MnCO3 microspheres in water vapor. Water vapor promotes the decomposition reaction and particle growth at low temperatures, resulting in the spontaneous formation of maze-like open macropores. Single-particle measurements of macroporous Mn3O4 microspheres reveal intrinsic compressive relaxation properties and electrochemical performance. In addition, the maze-like pore structure enables the collection of fine particles, which can be applied to fabricating functional composite materials. Thermal decomposition in water vapor will be a simple method of synthesizing macroporous particles without using pore-forming agents and templates.