Engineering of three dimensional (3-D) diatom@TiO2@MnO2 composites with enhanced supercapacitor performance

This work demonstrates a new and simple approach for fabrication a complex three-dimensional (3-D) composite for supercapacitor based on hollow diatom silica structures combined with interconnected coatings of TiO2 nanospheres and MnO2 mesoporous nanosheets (diatomite@TiO2@MnO2). The coating process is based on hydrolysis and metathetic reaction of TiF4 precursor followed by the reaction with KMnO4, which allows the coating of internal and external surface of diatom hollow structure with TiO2 and MnO2 layers. It was demonstrated that the introduction of anatase TiO2 layer on the 3-D diatomite@TiO2@Mn-2 electrodes provides a superior performance in terms of the specific capacitance, rate capability and resistance, showing critical role of an additional conductive layer on diatom surface. Moreover, by virtue of the unique 3-D structure, diatomite@TiO2@MnO2 electrode also displays a long cyclic stability (retain 94.1% after 2000 cycling) and a high coulombic efficiency (retain 98.2%-99.6% during 2000 cycling). The presented results show an enhanced supercapacitor behavior of the diatomite@TiO2@MnO2 electrodes prepared using a low-cost natural diatomite material and simple scalable process and confirm their evident potential for energy storage/conversion applications. (C) 2015 Elsevier Ltd. All rights reserved.