The stabilization of Ni(OH)2 by In2O3 rods and the electrochromic performance of Ni(OH)2/In2O3-rod composite porous film

•Electrochromic (EC) Ni(OH)2/In2O3-rods composite porous film was designed and constructed.•Stability of Ni(OH)2 film was obviously improved by the introduction of In2O3 rod array layer.•Improvement in film/substrate connection and EC performance was discussed and explained.•Effect of EC cycling on the microstructure and performance of composite film was analyzed. In this paper, a Ni(OH)2/In2O3-rod composite film with a porous structure was prepared by hydrothermal and solvothermal techniques using fluorine-doped tin oxide conductive glass as a substrate to improve the film/substrate connection and the cycle stability of the Ni(OH)2 film. A blank Ni(OH)2 film was also prepared for comparison purposes. The morphology, microstructure, and components of the films were characterized through X-ray photoelectron spectroscope, scanning electron microscope, and X-ray diffractometer. The electrochromic performance of the films including transmittance, cyclic voltammetry, cycle stability, electrochemical impedance, and switch speed was examined. The energy level positions and band gaps of the fluorine-doped tin oxide conductive glass and In2O3 layers were calculated based on their Mott–Schottky plots and ultraviolet-visible diffuse reflectance spectra. The results show that the In2O3 rods are approximately perpendicular to the substrate. The introduction of the In2O3 rod array transition layer enhanced the film/substrate connection in addition to providing favorable conditions for the nucleation and growth of Ni(OH)2, resulting in the improved Ni(OH)2 stability and porous structure as well as electrochromic performance. The mechanism of the improvement is explained in this paper.