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

Abstract

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.