Comparison of the lithium storage performance and electrochromic behavior of Prussian blue and its analogues

Nanosized Prussian blue (FeHCF), cobalt hexacyanoferrate (CoHCF), nickel hexacyanoferrate (NiHCF), copper hexacyanoferrate (CuHCF), and zinc hexacyanoferrate (ZnHCF) particles are prepared by facile chemical co-precipitation method. The microstructure of the samples is characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and N2 adsorption measurements. The lithium storage behavior and electrochromic performance of the five samples are systematically studied and compared. Among them, FeHCF presents two pairs of distinct charge/discharge plateaus; the other four samples exhibit one pair of charge/discharge plateaus, and plateau potential varies with the change of metal centers. During discharge and charge processes, the color of FeHCF can be reversibly switched in three colors (blue ↔ white ↔ green); while the CoHCF, NiHCF, CuHCF, and ZnHCF can be reversibly switched in two different colors corresponding to green ↔ red, yellow ↔ colorless, yellow brown ↔ dark red, and light yellow ↔ colorless, respectively. The results reported in this work could be helpful for rational design and performance regulation of Prussian blue analogues as electrochemical energy storage and electrochromic bifunctional materials.