Capacitive deionization (CDI) has been used to describe electrosorption with carbon electrodes by the mechanism of the electrical double layer (EDL) formation. Many studies have been conducted regarding new carbon materials that are also based on the same EDL mechanism to remove salt ions. It is considered mostly as physical sorption that occurs on the surface of the electrode, such electrodes that have limited adsorption capacity and has not yet achieved the breakthrough in capacitive performance for the commercial application. However, other mechanisms, such as pseudocapacitive behavior that result from either superficial or multi-electron transfer Faradaic reactions with fast electrosorption/desorption properties, have merged as a new front for investigation of better electrode materials. these classes of materials can offer greater capacity than EDL and with fast electrosorption/desorption properties as well.
Until now, this type of behavior can only occur in thin film electrodes with nanometer thickness and are not yet suitable for practical application. In this proposal, we address this pertinent issue by designing and synthesis the architectures that provide enhanced access of the metal centers not only by conductive graphene sheets that are in close contacting with the mixed spinel oxides, but also by the many openings offered via nanopores that are randomly distributed across the material structure. A two-step strategy is proposed: 1) synthesize the mixed spinel oxides in uniform nano-sized particles; and 2) use a 3D nanoporous graphene framework as the conductive scaffold for the electrochemically active materials. This morphology provides the anticipated synergistic effect between the pseudocapacitive electrosorption by mixed spinel metal oxides and the EDL by graphene. These architectures offer great potential that can remove the limitation of redox charge transfer of the hybrid electrodes, and result in high performance in removal of ions from water solution.