Preparation and electrochromic performance of NiO/TiO2 nanorod composite film

NiO/TiO2 composite film with a novel structure and electrochromic properties was prepared by combining the solvothermal and hydrothermal techniques. In order to verify the performance of the NiO/TiO2 film, a pure NiO film was prepared by the solvothermal technique for comparison. Fluorine doped tin oxide (F:SnO2; FTO) coated glass was used as substrate. The component, morphology and microstructure of the films were characterized by an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). The cyclic voltammetry (CV), cycle life, response time as well as transmittance of the films were investigated. The TiO2 film presents a tetragonal nanorod nature, while the NiO film grown on it is of a tremella-like porous structure, which is different with that of the pure NiO film. The nanorod structure of TiO2 film offered a three-dimensional frame for the growth of NiO film, forming an interpenetrating structure composed of TiO2 nanorods and NiO nanoparticles, and led to a good interface bonding with the FTO and NiO films. This special structure was proved to be beneficial to the optical modulation and coloration efficiency of the NiO film. Compared with the pure NiO film, the NiO/TiO2 film exhibits better reversible color change between transparency and dark brown, larger optical modulation, higher coloration efficiency, smaller attenuation and better cycling performance. (C) 2017 Elsevier B.V. All rights reserved.