Novel synthesis and formation process of uniform Mn2O3 cubes

Abstract

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.