Induced Synthesis of KMnF 3 from Wastewater Rich in High Concentration of Potassium Manganese and its Application in Supercapacitors

Abstract The co‐treatment of BRSW and EMAS produces a solution rich in potassium and manganese ions, making their high‐value utilization highly significant. This study developed a cost‐effective method using NaF as a single reagent to synthesize perovskite KMnF 3 material, optimizing the process parameters and ensuring material purity. The transformation mechanisms during precipitation are elucidated using AIMD. The material's phase, morphology, and crystal structure are extensively characterized. The electrochemical performances of KMnF 3 single electrode and supercapacitor assembled with AC are evaluated separately, and both KMnF 3 single electrode and AC//KMnF 3 supercapacitor exhibited superior cycling performance and operating voltage in 1 M Na 2 SO 4 electrolyte. The kinetics of three‐electrode and two‐electrode systems are further discussed, where the KMnF 3 single electrode exhibits diffusion‐controlled battery behavior, which begins to change to charge transfer control when assembled with alternating current into a supercapacitor. This process offers a low‐cost production advantage compared to other methods. According to LCA, this process is carbon emission‐reducing, energy‐efficient, and sustainable. The study provides a practical approach to wastewater resource utilization, offering a low‐cost, precision‐controlled synthesis method for KMnF 3 materials and supporting the development of green energy storage technologies.