Self-rising approach to synthesize hierarchically porous metal oxides

Hierarchically porous metal oxides are prepared using a novel self-rising approach. The method is ‘hard-template’ free and relatively easy to perform, utilizes inexpensive precursors and processing conditions, and is versatile, thus offering tremendous opportunities with a wide variety of conditions to explore to synthesize single or mixed metal oxides with hierarchically porous structures. Fe2O3, Sm0.2Ce0.8O1.9, LaFeO3, LaCoO3, and La0.5Sr0.5Co0.5Fe0.5O3 have been successfully synthesized while Fe2O3 and La0.5Sr0.5Co0.5Fe0.5O3 as examples for single and mixed metal oxides have been studied in detail. Sm0.2Ce0.8O1.9 has been applied as electrolyte for solid oxide fuel cells, showing good sinterability and high conductivity. A tentative scheme is provided to illustrate the pore formation mechanism using the self-rising approach.