Controllable Synthesis Of NiO Based Nanoporous Films And Their Electrochromic Properties

With the growing of the world population, environment pollution and energy shortage have become the biggest challenges which human being is faced currently. Electrochromic (EC) material has the characteristics of low cost, high efficiency, environmental friendly and intelligent, and it is a new kind of intelligent material that can alter the way of using solar energy. With adjusting and controlling the transmittance and heat radiation, electrochromic smart window can make full use of the solar energy, control the energy exchange for the interior of the buildings effectively, reduce power consumption and reduce the cost of lighting and temperature control. Electrochromic smart window can be widely used in intelligent building, automobile and aerospace fields. Among the numerous EC materials materials, NiO is a potential anodic EC material due to its large dynamic range, high electrochromic efficiency and low material cost. However, the slow switching speed, poor memory effect and low cycling durability have limited the commercial exploitation of NiO electrochromic film. The main objective in this research is to develop methods for enhancing electrochemical reaction kinetics of the EC films. We have developed methods such as chemical bath deposition and hydrothermal synthesis to fabricate NiO based porous structures films on FTO and investigated their electrochromic performance.Co-doped NiO electrochromic nanoflake array films grown on FTO with antireflection ability have been synthesized by low-temperature chemical bath deposition. Co doping has an influence on the growth and electrochromic properties of NiO nanoflake arrays. Noticeably, all the films show a very high transmittance at the bleached state in the region of visible light. Compared to the undoped NiO, the 1% Co-doped NiO nanoflake array film exhibits an outstanding electrochromism, including large transmittance modulation (88.3%), high coloration efficiency (47.7 cm2 C-1), fast switching speed (3.4 s and 5.4 s), excellent reversibility and cycling durability at a wavelength of 550 nm. The enhanced electrochromic performances can be attributed to the synergetic effect contribution from low crystallization, oblique nanoflake array configuration and improved p-type conductivity by appropriate Co doping.Hierarchical SnO2@NiO core/shell nanoflake array on FTO-coated glass has been synthesized by a facile two-step solution method toward energy-saving electrochromism. Noticeably, the SnO2@NiO core/shell nanoflake array film shows a sustained memory effect, which is conducive to saving energy in commercial application. The SnO2@NiO film exhibits an outstanding electrochromism, including large transmittance modulation (85.3%), fast switching speed (1.7 s and 2.4 s), high coloration efficiency (43.8 cm2 C-1), excellent reversibility and cycling durability at 550 nm. The enhanced electrochromic performances can be attributed to the unique core/shell architecture, which provides large amounts of active sites for electrochemical reactions, fast ion and electron transfer channels and good strain accommodation ability.