Multi-metal-doped transition metal compounds for high-performance asymmetric capacitive deionization

To address the limited ion adsorption capacity of carbon-based capacitive deionization (CDI) which primarily relies on double-layer mechanism, recent efforts have focused on the rational design and development of efficient Faradaic materials for CDI applications. In this study, we synthesized and applied Co- and Mn-doped transition metal compounds (Cu₂O@MCF) as the electrodes for asymmetric CDI using a simple hydrothermal method. The synthesized electrodes were analyzed using various characterization techniques, to confirm the successful doping and structural integrity. Electrochemical performance assessments revealed significant improvements in ion-capture capacity and overall desalination efficiency. Specifically, the optimized asymmetric CDI cell configuration, consisting of Cu₂O@MCF(Cl) as an anode and Cu₂O@MCF(Na) as a cathode, led to a significant increase in salt adsorption capacity (27.42 mg/g) over conventional symmetric carbon electrode (11.22 mg/g), an increase of over 2.4 times. Furthermore, the synthesized electrodes demonstrated effective phosphate ion removal, highlighting their potential applicability in wastewater treatment. The findings suggest that multi-metal doping significantly enhances electrode performance by synergistically combining electric double-layer capacitance and pseudocapacitance effects, due to their unique morphological and electrochemical properties. These results contribute to sustainable water treatment and resource recovery efforts, showcasing the effectiveness of the materials in improving CDI performance and opening new avenues for their application in environmental cleanup and resource management.