Synergizing Color Modulation with Energy Storage Capabilities through MXene Doping: Hybrid Electrochromic Supercapacitor and the Mechanism Therein

The rapid progress in fundamental technologies has sparked significant interest in multifunctional electronic gadgets with flexible and wearable capabilities, driving intense research into high-performance multifunctional devices. Here, a 2-fold approach is employed to design a multifunctional Ti₃C₂ MXene-doped methyl viologen (MV) and Prussian blue (PB)-based electrochromic energy storage device (Ti₃C₂-ECESD). First, role-specific components have been identified to achieve targeted functionality, and second, a density functional theory-based simulation in combination with experimental in situ voltage-dependent Raman measurements has been utilized to establish the working mechanism. The 2D material (Ti₃C₂ MXene), when used as a dopant, enhances the electrochromic properties and enables energy storage. Notably, an improved electrochromic property has also been achieved as the necessary prebleaching step was carried out in the device state configuration to avoid degradation due to side reactions in liquid solutions. The inclusion of Ti₃C₂ MXene in the device achieves a high color contrast of 84% with impressive coloration efficiency (506 cm²/C), durable stability over 1400 s, and a fast switching speed of ∼1.4 s. In conjunction with its improved electrochromic performance, the device exhibits good charge storage properties, characterized by fast charging and slow discharging, with a maximum specific capacitance of 33.4 mF/cm² at a current density of 0.4 mA/cm². To extend its on-site application, a flexible device has also been fabricated that can be easily bent or twisted, making it a promising candidate for real-life multifunctional applications in wearable electronic gadgets.