Synthesis of nanocrystalline manganese oxide powders: Influence of hydrogen peroxide on particle characteristics

Abstract

Nanocrystalline manganese oxide powders have been prepared at 25 °C by precipitation from Mn(NO3)2 aqueous solution. The presence and addition sequence of H2O2 significantly influence particle characteristics of the resulting manganese oxides, including crystal structure, particle size and morphology, and surface area, depending upon molar ratio of H2O2 with respect to Mn. The precipitation from preoxidized manganese solution by H2O2 results in flakelike-shaped amorphous hydrous manganese oxide (MnO2xH2O). In the absence of H2O2, on the other hand, amorphous Mn(OH)2 is obtained, and a part of Mn(OH)2 subsequently transforms into crystalline Mn3O4 by oxidation in air. Relative population of amorphous Mn(OH)2 decreases by dissolution when post-treated with H2O2. At Mn:H2O2 = 1:4, the well-defined 16-nm-sized nanocrystalline Mn3O4 with homogenous particle morphology is prepared. The treatment with excess H2O2, however, destroys crystalline Mn3O4 and leads to further oxidation of the aqueous manganese species. Under these conditions, a mixture of needlelike Mn2O3 and cubelike Mn3O4, including amorphous MnO2xH2O, is obtained.

Manganese oxide films for electrochemical supercapacitors

“…The reduction in sample weight below ∼600 • C can be mainly attributed to deposit dehydration. At temperatures exceeding 500 • C the weight loss can be also attributed to reduction of Mn 4+ species [25,26]. The weight loss at ∼900 • C can be related to the formation of Mn 3 O 4 [25,26].…”

Electrophoretic deposition of manganese dioxide–carbon nanotube composites

“…3) and corresponding endotherms (Fig. 4) can be attributed to the reduction of manganese dioxide and formation of Mn 3 O 4 at temperatures exceeding 1000 • C (Moon et al, 1999).…”

Sonochemical synthesis and chracterization of Mn3O4 nanoparticles

“…The oxygen octahedral is tetragonally distorted due to Jahn-Teller effect on Mn 3+ ions [6]. Various methods including high temperature sol-gel [7], sonochemical [8], co-precipitation [9], solvothermal [10], hydrothermal [11], chemical bath deposition [12], oxidation [13,14], microwave irradiation [15] and surfactant-assisted methods [16] have been reported for its synthesis.…”