Proton and Redox Couple Synergized Strategy for Aqueous Low Voltage-Driven WO3 Electrochromic Devices

Aqueous electrolytes possess non-combustibleand eco-friendly featurescompared to organic electrolytes, leading them to be more suitablefor application in smart windows for daily use. However, limited bythe narrow electrochemical window of water (1.23 V), its use in conventionalelectrochromic devices (ECDs) would result in irreversible performanceloss, which arises from decomposition caused by high voltage. Here,we propose a synergistic scheme combining a redox couple-catalyticcounter electrode (RC-CCE) strategy with protons as guest ions. Withthe help of the intelligent matching of the reaction potentials ofthe RC and amorphous WO3 electrochromic electrodes andthe highly active and fast kinetic features of protons, it successfullyreduces the working voltage range of the device to 1.1 V. The assembledHClO(4)-ECD can possess an overall modulation rate (350-1200nm) of 0.43 and 0.94 at -0.1 and -0.7 V, respectively,and a modulation of 66.8% at 600 nm at -0.7 V. Moreover, comparedwith other guest ions, the proton-based ECD exhibits higher colorationefficiency, a broader color modulation capability, and better stability.In addition, the house model equipped with the proton-based ECD effectivelyblocks solar radiation, which provides a potential solution for thedesign of aqueous smart windows.

Automated summary

Compared to organic electrolytes, aqueous electrolytes are non-combustible and eco-friendly, making them more suitable for daily use in smart windows. However, their use in conventional electrochromic devices is limited by the narrow electrochemical window of water, resulting in irreversible performance losses. This study proposes a synergistic scheme using a redox couple-catalytic counter electrode strategy with protons as guest ions to reduce the working voltage range of the device. The proton-based electrochromic device exhibits higher coloration efficiency, broader color modulation capability, and better stability compared to other guest ions.