Hollow bipyramid β-MnO2: Pore size controllable synthesis and degradation activities

•Hollow bipyramid β-MnO2 was prepared by hydrothermal method.•The pore size of the β-MnO2 can be precisely controlled by the concentration of HNO3.•β-MnO2 evolved from a nucleation–dissolution–recrystallization–etching process.

Hollow structured materials have found wide application in chemical catalysis and energy storage. Hollow bipyramid β-MnO2 was synthesized by the redox reaction between Mn2+ and ClO3− with concentrated nitric acid under hydrothermal conditions. The hollow pore size was precisely controlled by the concentration of HNO3 introduced to the reaction system. Generally, the more concentrated nitric acid was added, the larger pore size could form. The formation mechanism of such hollow structure was studied by time-dependent experiment using XRD and SEM characterizations. We also explored its degradation performance for methylene blue dye (MB) in the presence of hydrogen peroxide. The highest degradation efficiency could be obtained over the bipyramid β-MnO2 with the largest pore size of ca. 500 nm.

Graphical abstractHollow bipyramid β-MnO2 is prepared by hydrothermal method. The pore size of the β-MnO2 can be precisely controlled by the concentration of HNO3 introduced to the Mn2+ and ClO3− reaction system.Figure optionsDownload full-size imageDownload as PowerPoint slide