Diatom-Derived SiO2/N-Doped C Nanocomposite for Electrochemical Capacitors

Microalgae present a massive and untapped natural source of biomass for various applications. The fresh-water microalgae biomass was collected from Lake Uluabat in Turkey. Diatoms, which contain large amounts of SiO(2)in the form of cell walls, constituted 60%wt. of the biomass. SiO2/N-doped carbon nanocomposite (SiO2/NC) was obtained by an efficient MgO templating of the biomass conducted through hydrothermal carbonization and successive calcination. Despite its moderate specific surface area (250 m(2)g(-1)) and low C content (18%wt.), theSiO(2)/NCelectrode achieved a high specific capacitance (300 F g(-1)at 0.3 A g(-1), in 1 M H2SO4) due to pseudocapacitive contribution from heteroatoms (2%wt. N and 19% wt. O) and electric double layer contribution from interfaces expanded by SiO2. Interconnected network of micro- and meso- pores reinforced by SiO(2)provided enhanced rate capability and cycling stability (100% capacitance retention after 1500 cycles at 2 A g(-1)).