Crystalline-amorphous WO3 films with slit-shaped mesoporous structure via nanocellulose templating for electrochromic applications

Tungsten oxide (WO 3 )-based electrochromic materials have demonstrated significant potential for utilization in green energy applications, particularly in smart windows for buildings and thermal management in electric vehicles. However, the scalable production of environmentally friendly, low-cost WO 3 films with competitive electrochromic properties remains challenging. In this study, a facile and scalable sol-gel method was developed for the fabrication of Ti-doped WO 3 films with a crystal-amorphous composite structure, using nanocellulose as a bio-template. The introduction of a green renewable nanocellulose template resulted in the concurrent formation of a slit-shaped mesoporous morphology and oxygen vacancies. This process served to enhance the specific surface area and charge carrier concentration. It is noteworthy that the nanocellulose also modulated the film crystallization behavior under identical annealing conditions, generating optimized diffusion channels and abundant active sites. The resulting porous WO 3 films exhibited superior electrochromic performance, which provides viable approaches for pore-engineering strategies and crystallinity control in sol-gel derived porous WO 3 films. This offers practical references for processing methodology and structural design considerations.