Copper complex/polyoxometalate‐based tunable multi‐color film for energy storage

Abstract

Polyoxometalates (POMs) are considered as an attractive option for electrochromic energy storage (EES) system due to their unique electrochemical feature. Herein, a composite film NW/P 2 W 17 /Cu (phen) 2 based on Dawsontype monolacunary POMs K 10 P 2 W 17 O 61 (abbreviated as P 2 W 17 ) and copper complex [Cu II (phen) 2 ](NO 3 ) 2 (abbreviated as Cu (phen) 2 ) formed on TiO 2 nanowire (abbreviated as NW) array substrate was fabricated by hydrothermal process and layer-by-layer self-assembly combination method. This rational designed film NW/P 2 W 17 /Cu (phen) 2 exhibits excellent tunable multicolor electrochromic behavior and improved pseudocapacitive performance with large optical modulation (43.7% at 600 nm), fast switching time (t c = 2.9 s, t b = 9.5 s), and high volumetric capacitance (228.0 F cm À3 at 0.3 mA cm À2 ). In the process of charge and discharge, the composite film can realize the transformation from light green to orange, green, and finally to blue-green color, successfully achieve the bridge between electrochromic behavior and energy storage, and monitor the level of stored energy by color change. This work showed great potential of POMs-based electrode materials for integrated electrochromism and energy storage applications.

Reversible Zn2+/Al3+intercalation in niobium-substituted polyoxometalates and demonstration of energy storage smart windows

“…[7][8][9] Polyoxometalates (POMs) are a class of well-known metal oxide nano-clusters that exhibit excellent stability in reduced and oxidized states and can participate in the reversible electron transfer reaction, accompanied by multi-valence colored state species while retaining their structural integrity. [10][11][12][13] These unique features make POMs promising materials for EESDs, especially due to the diverse structures that can be obtained by substituting some tungsten (W) atoms in the POM molecule with transition metals. [14][15][16] It is worth noting that POM-based electrochromic materials suffer from limited electrolyte choices.…”