Copper Prussian Blue Nanoparticles with Varying Amounts of [Fe(CN)6] Defects as Supercapacitor Materials

Construction of the defect structure is a significant approach to optimize the electronic structure and promote the reaction kinetics. However, excessive defects will destroy the structure stability and further inhibit the performance of the electrode material. Herein, a series of copper Prussian blue (CuFe-PBA) nanomaterials with different contents of [Fe(CN)6] defects are synthesized by a simple chemical coprecipitation method using sodium citrate as a chelating agent and adjusting its ratio with copper ion. The effect of defect regulation on the crystal structure and the difference in the electrochemical properties of CuFe-PBA nanoparticles with different defect contents are studied. The experimental results indicate that reducing the defect content can significantly enhance the energy storage performances of PBAs. CuFe-PBA-2 has the maximum lattice parameters in all samples, ensuring rapid ion migration and electrochemical reaction kinetics, achieving a high specific capacitance of 220 F g–1 at 1 A g–1 and a superior rate capability with 86.4% of the initial specific capacity at 10 A g–1. Furthermore, the minimum [Fe(CN)6] vacancies increase the load-bearing capacity while guaranteeing the framework's flexibility, thereby enhancing structural stability and ensuring that CuFe-PBA-2 can provide an ultralong cycle life of 107.4% in 10,000 cycles. The hybrid device (CuFe-PBA-2//CNT) receives an energy density of 7.1 Wh kg–1 at a power density of 1.0 kW kg–1 and an energy density of 5.6 Wh kg–1 at a high power density of 7.0 kW kg–1. This work offers a method for regulating defects in CuFe-PBA nanoparticles and provides insight into the relationship between defects and electrochemical performances.