Designing TiO2/Au/Prussian blue heterostructures nanorod arrays for ultra-stable cycle and ultra-fast response electrochromism

Prussian blue (PB) is an anodic coloring candidate in the wide area of electrochromic (EC) applications. However, the co-influence of weak adhesion and low electrical conductivity leads to the poor stability and slow switching speed. To tackle this bottleneck, a novel TiO2/Au/PB nanorod array is designed through hydrothermal and electrodeposition approaches on fluorine-doped tin oxide (FTO) glass. Such a designed ternary array structure could not only increase reactive site and conductivity, but also improve ion storage capacity and promote charge transfer, attributed to the synergistic effect of TiO2/Au/PB core—shell heterostructure and the localized surface plasmon resonance (LSPR) effect of Au nanoparticles. Besides, density functional theory (DFT) calculation confirms the strong interaction between rutile TiO2 and FTO substrate, which contributes to the improvement of EC cycle stability. Benefiting from these effects, the TiO2/Au/PB film shows a fast coloration/bleaching response of 1.08/2.01 s (2.17/4.48 s, PB film) and ultra-stable EC performance of 86.8% after 20,000 cycles (50% after 600 cycles, PB film). Furthermore, the high-intensity light source can be shot clearly by the designed and assembled EC iris device (ECID) with TiO2/Au/PB film as an EC layer, while the photograph without an ECID is blurry, confirming the feasibility of the material in portable digital products.