Constructing Reversible Zn/MnO2 Dual-Electrodeposition-Based Smart Window with Wide Modulation Range by an Iodide Mediator in Near-Neutral Electrolyte

Abstract

Conventional reversible manganese dioxide (MnO₂) electrodeposition-based smart windows typically endure the constraints of narrow light modulation range, non-neutral color, and highly acidic electrolytes. Herein, novel Zn/MnO₂ dual-electrodeposition-based smart windows are constructed utilizing near-neutral electrolytes (pH = 5.74). The devices broaden the light modulation range of MnO₂ by reversible Zn electrodeposition, achieving a remarkable color change between transparent and neutral dark brown (chroma C^* = 9.48). Furthermore, an iodide (I⁻) as a redox mediator is used to significantly prolong the devices’ cycling durability by promoting the dissolution of MnO₂ and Zn. I⁻ chemically reduces MnO₂ to form Mn²⁺ and is oxidized to triiodide (I₃⁻), I₃⁻ then spontaneously oxidizes Zn to form Zn²⁺ and is reduced back to I⁻, thus completing one mediator cycle. Consequently, the devices with the I⁻ mediator exhibit impressive cycling durability (1,000 vs 60 cycles). Finally, the significant potential difference between the Zn and MnO₂ electrodes endows the devices with excellent energy storage performance. The study offers a line of thought for developing novel multifunctional devices.