Improved capacitive deionization by using 3D intercalated graphene sheet–sphere nanocomposite architectures

Capacitive deionization (CDI) is an alternative water purification technology offering a suitable way to obtain drinkable water. Electrode materials are quite crucial for the deionization efficiency. Here, for the first time, a straightforward and cost-effective approach is developed to prepare 3D intercalated graphene sheet–sphere nanocomposite architectures as high-performance CDI electrodes by using graphene oxide and [Ni₂(EDTA)] as precursors. 3D graphene nanospheres between graphene sheets inhibit the restacking of graphene layers. Significantly, the as-prepared 3D mesoporous graphene sheet–sphere nanocomposite architectures possess high specific surface area and suitable pore size distribution. By using 3D mesoporous graphene sheet–sphere nanocomposite architectures as an electrode, an ultrahigh electrosorptive capacity of 22.09 mg g⁻¹ is achieved in a 500 mg L⁻¹ NaCl solution at 1.2 V, and the salt removal percentage of the obtained electrodes is around 90%. Furthermore, the electrodes present good deionization stability and regeneration performance. This work also offers a promising solution to develop highly effective electrode materials in the CDI process for brackish and sea water desalination.