WO3 nanorods supported W18O49 nest-like composite film for enhanced electrochromic properties

WO 3 /W 18 O 49 composite film was synthesized by two-step hydrothermal reaction. • WO 3 improves structural stability and electrochemical reversibility of W 18 O 49 . • The composite film exhibits large optical modulation and high coloration efficiency. • Nest-like structure facilitates ion transport kinetics in electrochromic switching. • WO 3 nanorod skeleton boosts composite's stability: 86.5% retention after 500 cycles. W 18 O 49 with rich oxygen vacancies exhibits excellent interfacial contact as well as high electrical conductivity, which is a promising electrochromic material. However, the poor cycle stability limits its further practical application. In this work, hexagonal WO 3 was used as the growth skeleton of W 18 O 49 , and nest-like WO 3 /W 18 O 49 composite film was synthesized by two-step hydrothermal reaction, favoring the enhancement of optical modulation and cycle stability. The porous WO 3 /W 18 O 49 composite film exhibits an optical modulation of 56.9% at 633 nm, fast response time (colored/bleached time = 8.1/2.4 s), good coloration efficiency of 93.2 cm 2  C −1 . Moreover, the optical modulation of the composite film can maintain 85.6% of the initial modulation after 500 cycles. This work provides a feasible and effective two-step hydrothermal synthesis route to enhance the cycle stability of W 18 O 49 -based electrochromic materials.