Accelerating the decomposition of KMnO4 by photolysis and auto-catalysis: a green approach to synthesize a layered birnessite-type MnO2 assembled hierarchical nanostructure

Abstract

In this work, we developed a facile, green and low-cost strategy for the controllable synthesis of birnessite-type MnO₂ (Bir-MnO₂) nanosheets assembled in a “desert rose”-like 3D hierarchical nanostructure and proposed a two-step growth route, namely photolysis and followed by auto-catalytic decomposition of KMnO₄. Bir-MnO₂ nanosheets were first obtained under the irradiation of a light source and acted as seeds for further decomposition of the excess MnO₄⁻ in the dark. The sizes of the Bir-MnO₂ 3D hierarchical nanostructures could be readily controlled by varying the concentration of KMnO₄, the light source and the pH value. Furthermore, Bir-MnO₂ nanosheets on CNTs were successfully fabricated utilizing the same strategy without the addition of any surfactants or organic templates. It is anticipated that the fabrication of Bir-MnO₂ based nanostructures and composites could be beneficial from this universal method.