Synthesis of zinc oxide based nitrogen doped graphene oxide with polyaniline (ZnO/N-GO/PANI) flow electrode for desalination application using flow capacitive deionization

This work reported the synthesis of zinc oxide (ZnO) based nitrogen doped graphene oxide (N-GO) with polyaniline (PANI) composite (ZnO/N-GO/PANI) as a potential flow electrode for flow capacitive deionization (FCDI). The prepared ZnO/N-GO/PANI composite was characterized for its structural property, stability, thermal decomposition and surface area analysis using X-ray diffractometer (XRD), scanning electron microscope (SEM), thermo-gravimetric analyzer (TGA) and Brunauer–Emmett–Teller (BET) respectively. Electrochemical studies were performed for the ZnO/N-GO/PANI composite using an electrochemical workstation with a three-electrode setup. SEM analysis revealed that the ZnO/N-GO/PANI composite architectures are made up of spherical and flake-like particles with an average particle size of ~ 32 nm. XRD results confirmed the crystalline nature of the ZnO/N-GO/PANI composite with sharp and intense peaks. BET analysis revealed that ZnO/N-GO/PANI composite has a greater surface area and pore size of 31.65 m² g⁻¹ and 66.981 nm respectively than ZnO/N-GO composite of 15.98 m² g⁻¹ and 42.09 nm. The prepared ZnO/N-GO/PANI composite exhibited a higher specific capacitance of 628.4 F g⁻¹ in 0.1 M KCl electrolyte solution determined using cyclic voltammetry (CV) studies. The proposed ZnO/N-GO/PANI composite was identified to be a favourable electrode for flow capacitive deionization (FCDI) technique. The FCDI results revealed that ZnO/N-GO/PANI flow electrode has a high electrosorption capacity (288 mg g⁻¹) and desalinating efficiency (38.1%) under a 1000 mg L⁻¹ of sodium chloride (NaCl) solution at 1.2 V. Therefore, the proposed ZnO/N-GO/PANI composite was identified to be a promising electrode material for FCDI operation.