Capacitive deionization performance of asymmetric nanoengineered CoFe₂O₄ carbon nanomaterials composite

Capacitive deionization (CDI) is a relatively new technique that uses electric double layer (EDL) effects, high-affinity chemical groups, redox-active materials, and membrane capacitive electrosorption principle for the desalination. In this paper, hydrothermal synthesis of cobalt ferric oxide (CFO) metal oxide nanoparticles (NPs) coupled with the vacuum filtration method, or the freeze-drying method is used to fabricate high-performance nanocomposites: CFO-graphene, CFO-CNTs, and CFO-3DrGO. Two times of hydrothermal reaction methods were conducted to fabricate the CFO-3DrGO nanoengineered as a pseudocapacitive/EDL electrode. The results have demonstrated that the SAC of CFO-3DrGO/CFO (64.5 mg g^-1) is greater than that of the CFO-graphene/CFO (55.16 mg g^-1) and CFO-CNTs/CFO (21.5 mg g^-1) due to the better surface area of the CFO-3DrGO nanocomposite (330 m² g^-1). The higher surface area of the CFO-3DrGO is due to the porous and interconnected 3D structure of the 3DrGO, and it provides a larger surface area to form EDL capacitance. In addition, the added porous 3DrGO entangled with the spinel crystals (CoFe₂O₄) in the composite allowed for a quick ion diffusion across the interconnected open macroporous structures.