MnO2 nanostructures with three-dimensional (3D) morphology replicated from diatoms for high-performance supercapacitors

Herein, we demonstrate the synthesis of size- and shape-controlled MnO2 nanostructures by replica molding from diatom silica structures for high-performance supercapacitors. Three types of hierarchical hollow MnO2 patterns with different three-dimensional (3D) structures, shapes and large surface areas were successfully prepared from three diatom species by a template-assisted hydrothermal process. The extraordinary precision and nano-scale resolution of 3D replications of complex biological architecture from diatoms to artificial MnO2 structures are confirmed. Detailed electrochemical measurements reveal that the Melosira-type MnO2 pattern exhibits not only a high specific capacitance of 371.2 F g(-1) at a scan rate of 0.5 A g(-1), but also relatively good cycle stability (93.1% capacitance retention after 2000 cycles at a scan rate of 5 A g(-1)), demonstrating a promising application as supercapacitor electrode materials.