Synthesis and application of NiO-ZrO₂@g-C₃N₄ nanocomposite for high-performance hybrid capacitive deionisation

The desalination of saline water from the ocean and estuaries provides about 65 % of the global freshwater supply. Desalination technology development is dependent on a reliable and cost-effective electrode material. This research is focused on the synthesis and application of NiO-ZrO₂@g-C₃N₄ nanocomposite for the desalination of saline water by the hybrid capacitive method. NiO-ZrO₂@g-C₃N₄ was synthesized by a solid-state reaction. It was then used to modify the activated carbon electrode. This was applied as an electrode in a CDI cell for the desalination of saline water. The highest ion adsorption capacity recorded is 24.45 mg/g at 1.2 V applied voltage and an electrolyte concentration of 800 mg/L, while the optimum salt recovery efficiency was recorded at 42.7 % with the 300mb/L solution. The specific capacitance of the NiO-ZrO₂@g-C₃N₄ composite is 550F/g at a scan rate of 10 mV/s in a 1.0 M KCl solution, and that of g-C₃N₄ is 300F/g at a scan rate of 10 mV/s, in a 1.0 M KCl solution. The NiO-ZrO₂@g-C₃N₄ composite also displayed excellent electrochemical stability after nine cycles of adsorption/desorption measurements. The result implies that NiO-ZrO₂@g-C₃N₄ is an ideal electrode material for application in desalination by the hybrid capacitive deionisation method.