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

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous electrolytes offer non-combustible and eco-friendly advantages over organic electrolytes for smart windows.
• The narrow electrochemical window of water (1.23 V) limits the performance of conventional electrochromic devices (ECDs) due to high-voltage-induced decomposition.

Purpose of the Study:

• To overcome the limitations of aqueous electrolytes in electrochromic devices.
• To develop a high-performance, stable, and safe aqueous smart window technology.

Main Methods:

• Proposed a synergistic scheme combining a redox couple-catalytic counter electrode (RC-CCE) strategy with protons as guest ions.
• Intelligently matched the reaction potentials of the RC and amorphous WO₃ electrochromic electrodes.
• Utilized the high activity and fast kinetics of protons.

Main Results:

• Successfully reduced the working voltage range of the device to 1.1 V, preventing water decomposition.
• The assembled HClO₄-ECD demonstrated significant optical modulation rates (0.43-0.94 across 350-1200 nm) and high modulation (66.8% at 600 nm).
• Proton-based ECDs exhibited superior coloration efficiency, broader color modulation, and enhanced stability compared to devices with other guest ions.

Conclusions:

• The developed proton-based ECD strategy effectively addresses the electrochemical window limitation of aqueous electrolytes.
• The proton-based smart window shows potential for practical applications, including effective solar radiation blocking in a house model.
• This work provides a viable solution for designing advanced aqueous smart windows.