Synthesis of perforated single-crystalline Mn2O3 microcubes for thermocatalytic applications†

Transition metal oxides (TMOs) are increasingly viable choices for catalytic applications because of their tendency to exhibit variable oxidation states depending on the chemical environment and the possibility of enhancing surface activity through morphology control. The development of efficient and cost-effective methods for the synthesis of TMOs with meso-to nanoscale morphologies and improved characteristics remains a significant challenge. Herein, we report a template-free synthesis strategy for the preparation of perforated mesoporous manganese(III) oxide microcubes (PMOM) through a morphology-conserved transformation of the precursor method. The formation of PMOM with cubic structures and pore sizes in the range of 20 nm was confirmed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Mn₂O₃ samples exhibited a Swiss cheese-like porous structure with a particle size of 0.70 to 1.2 μm. Furthermore, the catalytic activity of the synthesized PMOM samples on the thermocatalytic decomposition of ammonium perchlorate (AP), an oxidizer used in solid propellants, was investigated. The transition between Mn³⁺ to Mn²⁺ oxidation states facilitates the transfer of electrons, allowing the metal surface to act as an electron acceptor during the oxidation of water molecules. Due to the oxidation–reduction cycle occurring on the surface, a considerable number of electrons are available for promoting surface reactions. Thus, the (211) surface of PMOM enhanced the thermal decomposition of AP, and a plausible mechanism for this catalytic activity was proposed.