Keggin-type polyoxometalate–PW12 regulates the localized surface plasmon resonance effect of W18O49 to enhance electrochromic performance

As a tungsten oxide with a unique stoichiometric ratio, W 18 O 49 exhibits localized surface plasmon resonance (LSPR) effects that significantly enhance its electrochromic (EC) properties; however, the modulation mechanism of this enhancement remains underexplored. In this study, we use Keggin-type H 3 PW 12 O 40 (PW 12 ) and W 18 O 49 to successfully fabricate a film (W 18 O 49 /PW 12 ) with high transmittance via the Layer-by-Layer (LbL) method. The films exhibit coloration efficiencies of 91.65 and 156.58 cm 2 /C at 650 and 1100 nm, respectively, and a specific capacitance of 14.34 mF/cm 2 . Although the EC performance of PW 12 is negligible, its multi-electron structure and interactions with W 18 O 49 increase the concentration of oxygen vacancies in the W 18 O 49 /PW 12 film, thereby enhancing the LSPR effect. The bandgap of the W 18 O 49 /PW 12 film decreases, resulting in superior EC ability and energy storage activity, while achieving a thermal blocking efficiency of 54.94 %. The W 18 O 49 /PW 12 film combined with NiO is assembled into electrochromic devices (ECDs) that achieve a thermal blocking efficiency of 79.12 % at −2.3 V. This study is pivotal for elucidating the mechanism by which polyoxometalates regulate the LSPR effect of W 18 O 49 and offers new insights into the development of multifunctional ECDs that integrate light and thermal modulation, as well as energy storage.