High-Performance and Stability Electrochromic Devices with a Water Isotopologue.

In this report, an ammonium metatungstate (AMT) and ferrous chloride [Fe(II)Cl 2 ] electrochromic liquid (ECL) was synthesized using a hydrothermal method, with D 2 O used as the solvent instead of H 2 O. The results show that the use of D 2 O can improve the stability and performance of ECLs. The hydrogen evolution process in electrochromic devices (ECDs) filled with ECL becomes more difficult, while the material exchange process becomes easier. The ECD exhibits a color modulation amplitude of 58%@680 nm at 2 V. After 500 cycles, the device's performance remains above 95% at a current density of 1.5 mA/cm 2 . Hydrogen bonds in D 2 O solutions are expected to exhibit stronger forces compared to those in regular H 2 O solutions. Therefore, we hypothesize that enhancing the strength of hydrogen bonds in H 2 O solutions is an effective approach for improving the performance and stability of electrochromic solutions.