High-Performance and Stability Electrochromic Devices with a Water Isotopologue

In this report, an ammonium metatungstate (AMT) and ferrous chloride [Fe(II)Cl₂] electrochromic liquid (ECL) was synthesized using a hydrothermal method, with D₂O used as the solvent instead of H₂O. The results show that the use of D₂O 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/cm². Hydrogen bonds in D₂O solutions are expected to exhibit stronger forces compared to those in regular H₂O solutions. Therefore, we hypothesize that enhancing the strength of hydrogen bonds in H₂O solutions is an effective approach for improving the performance and stability of electrochromic solutions.