Periodically ordered inverse opal TiO2/polyaniline core/shell design for electrochemical energy storage applications

Abstract

In the present work, a unique core/shell structured TiO2/polyaniline (PANI) nanocomposite is successfully fabricated by chemically depositing PANI nanorods on a periodically arrayed TiO2 inverse opal (IO) structure for energy storage applications. The morphology, composition, and electrochemical behavior of the TiO2/PANI core/shell structure are studied and compared with those of the PANI nanorods on stainless steel substrate. Field emission scanning electron microscopy (FE-SEM) and transmission electron spectroscopy (TEM) studies confirm the formation of a PANI nanorod shell structure on the core of the TiO2 surface. A large specific capacity of 196.59 mA h g(-1) at a scan rate of 5 mV s(-1) is achieved for TiO2/PANI electrode which is comparable to that of TiO2 (2.83 mA h g(-1)) and PANI (95.86 mA h g(-1)) electrodes. Such improvement is ascribed to PANI with a high capacity and excellent conductivity, and the TiO2 IO structure with a large surface area and interconnected macropores, allowing efficient PANI nanorod loading, mass transport, and rapid charge transfer. A symmetric energy storage device is fabricated by assembling the two pieces of TiO2/PANI with a H2SO4 gel electrolyte. The device shows the high energy density of 20.36 Wh kg(-1) at a power density of 500 W kg(-1) with good cycling stability (78% for 1000 cycles).