A MOF-derived Zn-TiO2 electrochromic supercapacitor

Abstract

Electrochromic supercapacitors caused widespread concern due to their ability to exhibit color changes to monitor the charging and discharging states. However, the unsatisfactory energy storage and electrochemical durability seriously hinder their practical applications, especially for titanium dioxide (TiO2) electrochromic supercapacitors. To address the above issues, a strategy for designing the novel bi-functional Zn-TiO2 film derived from the metal-organic framework (MOF)-based material is proposed for the first time. The ZnO@zeolitic imidazolate framework-8 (ZIF-8) acts as the self-sacrificial template, beneficial from the diverse porous structure of ZIF-8 and the core-shell structured of ZnO@ZIF-8, the obtained Zn-TiO2 film inherits the large pore volume and specific surface area, facilitating ion/electron intercalation/deintercalation and transport, presenting good electrochemical performance, large specific capacitance, and good constant current charging and discharging stability. In addition, the persistent deintercalation of the embedded Zn2+ in the TiO2 lattice continuously generates new available sites for Li+ intercalation, and the highly porous structure of Zn-TiO2 provides sufficient space to cope with the volume expansion during the electrochemical cycling, leading to the superior durability of the film. Finally, an asymmetric electrochromic supercapacitor using the Zn-TiO2 electrode is constructed and investigated. This study promotes the exploration for designing and fabricating the high-performance electrochromic supercapacitors towards intelligent technology applications.