Synthesis and Crystal Structure Control of Nano-Sized Mno2 Particles Using Various Mn Source Materials by Hydrothermal Process

Single phase of nano-sized α-, β- and γ-MnO2 particles with a high crystallinity were successfully synthesized by a hydrothermal process using different Mn source materials such as Mn(OAc)2, MnSO4, MnCl2 and Mn(NO3)2. By changing the Mn source materials, the crystal structure and particle morphology of the MnO2 could be effectively controlled. The samples with Mn(OAc)2 and MnSO4 showed α- and β-MnO2 having rod shape, and those with MnCl2 and Mn(NO3)2 showed the γ-MnO2 having the aggregated angular nanoparticles. From the XPS analysis, β-MnO2 sample showed a high ratio of Mn4+ and Olett on the surface, while α- and γ-MnO2 samples showed a lower valence of Mn such as Mn3+ and Mn2+ on the surface and the ratio of Olett is also low.