Electrochemically capacitive deionization of copper (II) using 3D hierarchically reduced graphene oxide architectures

Abstract

Herein, we have developed the simple and novel 3-dimensional reduced graphene oxide (3D rGO) with large specific surface and superior electrochemical performance for capacitive deionization (CDI) of Cu2+ ions. The graphene oxides, produced from graphite powder by the modified Hummers method at pH 5, can be directly reduced into 3D rGO structures through the hydrothermal process at 150 °C for 12 h. The SEM/TEM images clearly indicate that 10–50 μm rGO can constitute the ordered structures with continuously inter-connected in-plane nanopores and micropores in 3D architecture, which can not only increase the surface area to 662 m2 g−1 but also facilitate the rapid transport of electrons and electrolyte ions. The 3D rGO exhibits an excellent electrochemical performance and the specific capacitance of 3D rGO is 508F g−1 at a scan rate of 5 mV s−1. Moreover, the applicability of 3D rGO was examined by CDI for the removal of Cu2+ ions. The electrosorption capacity of 3D rGO toward Cu2+ adsorption is 18.1 mg g−1 at 1.0 V. In addition, the electrosorption of Cu2+ ion follows the pseudo-second-order kinetics. Results of this study clearly demonstrate the excellence of 3D rGO to serve as a superior electrode material for Cu2+ ions removal, which can open a new way to design 3D rGO based composites for a wide variety of applications including water purification, catalysis and energy conversion and storage.