Enhanced electrochromic properties of inorganic–organic tungsten oxide and Prussian blue core–shell film

Prussian blue (Fe 4 [Fe(CN) 6 ] 3 , PB) has become a widely studied anodic electrochromic material due to its advantages such as large optical modulation range, fast response speed and low voltage demand. Tungsten oxide (WO 3 ) as a cathode electrochromic materials, have various advantages, while their low color rendering efficiency and poor cycling stability limit their applications. To this end, the following solution was proposed for the first time in this study: the hydrothermal method was adopted to prepare tungsten oxide nanorods and then coat Prussian blue on the rod-shaped tungsten oxide to form an inorganic–organic core–shell structure (WO 3 /PB) to improve electrochromic performance. Through comparative experiments, the effects of WO 3 /PB core–shell structure for the electrochromic properties of films and its mechanism were explored. The Li + diffusion coefficient of WO 3 /PB core–shell structure films is 35% and 720% higher than that of single WO 3 and PB, respectively. At the same time, compared with the single PB and WO 3 films, the electrochromic response speed of the WO 3 /PB film is fast, and the light transmittance after coloring is low, with good optical properties. Relevant experimental data displayed that WO 3 is wrapped by PB to form a core–shell structure, which makes the film have high electrochromic properties. The reasons are the formation of electron pair donor–acceptor system in the film and the formation of double electrochromic effect. WO 3 /PB forms a rod-like nano core–shell structure, which increases the surface area for the reaction and facilitates the transfer of ions and electrons into and out of the film. This method of combining anodic electrochromic materials and cathodic electrochromic materials to form a core–shell structure to improve electrochromic performance provides a new direction for future electrochromic research.