Novel synthesis and formation process of uniform Mn2O3 cubes

Uniform Mn2O3 cube with an average particle size of 4 μm is synthesized via a hydrothermal treatment of H-type layered manganese oxide in tetramethylammonium hydroxide (TMAOH) solution at 180 °C for 24 h. The as-prepared materials are characterized by XRD, SEM, TEM, XPS, TG-DTA, and IR and the formation process of Mn2O3 cubes is also investigated. TMA+ ions play an important role for the formation of Mn2O3 with good crystallinity and regular cubic morphology. The intercalation of TMA+ ions into the layered manganese oxide firstly causes a short-range swelling expansion of the interlayer, and the swelled layered manganese oxide is exfoliated into their elementary host sheets by a hydrothermal treatment. Some Mn(III) probably migrates into the solution and Mn(IV) is reduced by methanol decomposed by TMAOH in the hydrothermal system, and forms Mn2O3 crystal nuclei under suitable hydrothermal condition. TMA+ ions in the solution are selectively adsorbed on the (100) planes of Mn2O3 crystal nucleus, and finally generates Mn2O3 particles with cubic morphology.