Multicolor reversible prussian white film with application in self-powered electrochromic device

Abstract

Prussian blue (PB) is considered a potential electrochromic material owing to its open structure, simple synthesis and reversible conversion of multicolor, and studies are focused on its color change of transparent ↔ blue. However, the multicolor conversion of transparent ↔ blue ↔ green ↔ yellow has rarely been reported because the alkali metal ion in the existing PB film is lower in concentration than its standard chemical formula, which makes the complete oxidation from PB to Prussian yellow (PY) unachievable. Herein, the Na-rich rhombic Prussian white (PW) is synthesized via the hydrothermal method, and its mechanism of multicolor conversion is studied. Benefitting from the adequate sodium, the PW film exhibits outstanding electrochromic performance with the reversible multicolor change of transparent ↔ blue ↔ green ↔ yellow and excellent cycling stability (52.1% of capacity retention after 300 cycles). Simultaneously, the long cycling stability and high coloration efficiency of the PW film are also revealed in the process of PW ↔ PB. In addition, the self-powered electrochromic device with the system of Zn||PW||Pt@CC is constructed, and it realizes fast coloring response time (26.3 s) and high reversibility. The reversible multicolor conversion and excellent cycling stability of the PW film make it a promising candidate for applications such as camouflage and high-performance smart windows.