Manganese ferrite decorated N-doped polyacrylonitrile-based carbon nanofiber for the enhanced capacitive deionization

In this study, the manganese ferrite was decorated onto 1-dimensional based activated carbon fiber (MnFe₂O₄/N-ACF) by precipitation method for capacitive deionization (CDI) application. Polyacrylonitrile (PAN) and 2-methylimidazole (2MI) were used as the carbon precursor and nitrogen dopant for the fabrication of 200 nm N-doped ACF (N-ACF). After the deposition of 5–15 wt% MnFe₂O₄ nanoparticles, the diameter of MnFe₂O₄/N-ACF increases to 300–400 nm, and the addition of 10 wt% MnFe₂O₄ can well deposits onto the surface of N-ACF to decrease the impedance to accelerate the electron transfer as well as to enhance the specific capacitance up to 422 F g⁻¹ at 5 mV s⁻¹. Furthermore, the CDI Ragone plots indicate that the specific electrosorption capacity (SEC) of NaCl by 10 wt% MnFe₂O₄/N-ACF is in the range of 23.4–41.2 mg g⁻¹, which is a function of applied voltage, NaCl concentration, and flow rate. A SEC of 41.2 mg g⁻¹ in the presence of 500 mg L⁻¹ can be achieved when the flow rate and applied voltage are 10 mL min⁻¹ and 1.4 V, respectively. Moreover, the as-prepared electrode materials can be recycled for at least 50 cycles and the SEC can be maintained over 93% of the original activity after 50 cycles, indicating the excellent cycling stability of MnFe₂O₄/N-ACF electrode. Results obtained in this study signify that the 1-D MnFe₂O₄/N-ACF is a promising CDI electrode material, which can provide a productive solution for elevating the platform with low cost and high efficiency for CDI technology.