Abstract
In order to achieve optimal desalination during capacitive deionization (CDI), CDI electrodes should possess high electrical conductivity, large surface area, good wettability to water, narrow pore size distribution and efficient pathways for ion and electron transportation. In this work, we fabricated a novel CDI electrode based on a three-dimensional graphene (3DG) architecture by constructing interconnected graphene sheets with in-plane nanopores (NP-3DG). As compared to 3DG, NP-3DG features a larger specific surface area of 445 m2 g−1 and therefore the higher specific capacitance. The ultrahigh electrosorptive capacity of NP-3DG predicted from Langmuir isotherm is 17.1 mg g−1 at a cell potential of 1.6 V. This can be attributed to the interconnected macropores within the graphene networks and nanopores on graphene sheets. Both of macropores and nanopores are favorable for enhancing CDI peroformance by buffering ions to reduce the diffusion distances from the external electrolyte to the interior surfaces and enlarging the surface area.
Highlights
The concept of capacitive deionization (CDI) follows the working principle of an electrical double-layer capacitor (EDLC)
The reduction process can cause graphene oxide (GO) sheets to agglomerate due to their strong π –π interactions and this leads to uncontrollable pore size distribution and low accessible surface areas, which significantly limit their practical usage in CDI applications[27,28]
NP-3DG was prepared by a facile hydrothermal process, in which GO sheets were converted to reduced GO and assembled into a three-dimensional architecture (See Materials Synthesis Section)
Summary
The concept of CDI follows the working principle of an electrical double-layer capacitor (EDLC). The nanopores on graphene sheets can further enlarge the surface area and improve both electrosorption capacity and ion transport (see Fig. 1). An ultrahigh electrosorptive capacity of 17.1 mg g−1 was achieved at a cell potential of 1.6 V, which is among the best performance of previous reported graphene-based electrodes for CDI.
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