A review on recent advances in Prussian blue, its analogues, and their derived materials as electrodes for high performance supercapacitors

Supercapacitors (SCs) have gained much attention as an environmentally friendly and efficient energy storage system, especially for high-power applications. Among the various electrode materials, Prussian blue, and its analogues (PB/PBAs) have gained prominence due to their tunable chemical composition and open framework structure. PB/PBAs have been used as an electrode material in their natural state and used to fabricate diverse metal heterostructures for energy storage devices. These materials offer advantages such as simplicity of fabrication, non-toxicity, and cost-effectiveness. Because of their unique compositions, PB/PBAs usually contain two or more kinds of metallic elements, and the synergistic effect between the different metallic elements provides more possibilities for their application in the field of SCs. After easy treatment of PB/PBAs, derived materials, such as transition-metal carbide, transition-metal oxide, transition-metal selenide, transition-metal sulfide, and so forth can be obtained. Due to the particularity of PBA composition, these derived materials are usually bimetallic or polymetallic. These derivatives not only inherit the structural advantages of PB/PBAs, but also usually solve the problem of poor conductivity of PB/PBAs. Therefore, derived materials can show more excellent electrochemical performance. In recent years, the preparation and electrochemical application of PB/PBAs and their derivatives have attracted increased attention. In this article, the synthesis strategies of PB/PBAs and their derived materials are systematically summarized. The applications of related materials in the field of SCs are introduced in detail. And the prospects and challenges are further analyzed.