Hydrothermally controlled synthesis of 3D dendrite MnOOH nanorods through self-assembly of MnO2 nanoparticles in acid solution

In this work, we report a novel self-assembly of zero-dimensional (0D) MnO2 nanoparticles into three-dimensional (3D) dendrite MnOOH nanostructures via the hydrothermal method without any template or surfactant. Through characterization techniques including field emission scanning electron microscopy (FESEM) and high-resolution-transmission electron microscopy (HRTEM), we found that the morphologies of obtained 3D dendrite MnOOH nanostructures could be controlled via fine tuning process temperature, amount of MnO2 nanoparticles and solution media. The results also demonstrated that the weak acid hydrothermal solution and high temperature favored the hydrothermal growth of uniform 3D dendrite MnOOH nanostructures. Further evidence of time-dependent experiments revealed that oriented attachment and structure defects played an important role in the formation of such dendrite MnOOH nanorod. In principles, these findings could be useful for other metal oxides to fabricate their novel nanostructures for electrochemical electrodes.