Preparation And Capacitive Desalination Performance Grapheme-based Carbon Material

As a serious global problem, the shortage of freshwater poses one of the greatest threats to humanity, due to the increasing demand for drinking water caused by the growing population. Capacitive deionization(CDI) was the least energy consuming and the most reversible deionization technology. Nowadays CDI attracts great interest, because no chemicals are neede d and no contaminants are produced during the environmentally-friendly process. With high electrical conductivity and large accessible surface area, carbon-based materials had been considered as the favoured electrode materials for CDI, such as activated carbon, carbon aerogels, carbon nanotubes, porous carbon and graphene.So our research commite to prepare porous carbon-based material with high graphitization, large specific surface area and superior desalination performance. We have synthesized graphene-like carbon nanosheets(GCNS), two-dimensional Nitrogen-doped Porous Carbon/Graphene(NPCG) nanosheet and three-dimensional graphene coated mesoporous carbon sphere(3DG@OMCS) composite material via a simple method. The main rearch contents are listed as followed:1) we developed a facile method of fabricating graphene-like carbon nanosheets(GCNS) by a Fe-catalyzed glucose-blowing approach. Glucose is used as carbon precursors, NH4 Cl as blowing agents and Fe species as graphitization catalyst. GCNS possesses a similar height with few-layered grapheme, the thickness of GCNS is appr oximately 2.4 nm which means seven graphitic layers. For comparison, the carbon material with few nanosheet was produced in the same procedure without Fe(NO3)3?9H2O, which was denoted as C-1. The product of direct annealing glucose without NH4 Cl and Fe(NO3)3?9H2O was denoted as C-2. The electrosorption behaviour was carried out by the CV measurement indicates that the GCNS electrode show evidently the largest specific capacitance. The galvanostatic charge/discharge measurements demonstrated that, compared to C-1and C-2, the GCNS electrode exhibits an excellent cyclic performance and good reversibility.The CDI performance, adsorption kinetics and electrosorption isotherms of the electrodes are evaluated by a batch mode electrosorptive experiment.It is shown that the electrosorptive capacity of GCNS is 38.62 μmol/L, much higher than that of C-1 and C-2. The good electrical conductivity owing to the high graphitization degree of GCNS and the ultrathin graphene-like nanosheets could provide more active site for CDI application. In addition, a comparative study was carried out to explore the electrosorption behavior of GCNS from a point view of adsorption kinetics and thermodynamics. The result indicates that the GCNS electrode not only own the maximum adsorption capacity, but also it is the monolayer adsorption.2) Employing an appropriate graphene/silica nanosheet template, we have developed a novel Nitrogen-doped Porous Carbon/Graphene(NPCG) composite. The template is built up by the direct growth of the electrostatic assembly of colloidal silica nanoparticles(NPs) on a graphene oxide(GO) surface. The NPCG shows a close relationship between the electrochemical performance and content of GE. The transmission electron microscopy, scanning e lectron microscope and nitrogen adsorption/desorption analysis indicated that uniform mesoporous structures were well retained and the composite revealed improved specific surface area. The CV and galvanostatic charge/discharge measurements were employed to investigate the electrosorption performance of NPCG composites and GR. Noteworthy, the NPCG composite electrode with the Nitrogen-doped Porous Carbon content of 72%(NPCG-72) showed the highest specific capacitance. In addition, the desalination behaviour, adsorption kinetics and electrosorption isotherms of the fabricated electrodes evaluated by a batch mode electrosorptive experiment. The results indicated that the NPCG-72 electrode displayed much higher desalination capacity and deionization efficiency. The excellent deionization performance of the NPCG-28 is attributed to its large specific surface area and high conductivity, which not only provide more active sites for CDI application, but also decreased the inner resistance cost. In addition, a comparative study was carried out to explore the electrosorption behavior of NPCG-28 from a point view of adsorption kinetics and thermodynamics. The result indicates that the NPCG-28 electrode not only own the maximum adsorption capacity, but also it is the monolayer adsorption.3) A three-dimensional graphene coated mesoporous carbon sphere(3DG@OMCS) composites have been prepared via a simple template-directed method using OMCS@Si O2 as hard templates. The structural properties indicates that the mosoporous carbon sphere can be inserted into the cavity of the three-dimensional graphene. The mesoporous carbon sphere can efficiently prevent the aggregation of graphene. The electrochemical performance shown that the 3DG@OMCS electrode displayed higher capacitance than that of pure OMCS or 3DG. Also, compared to OMCS and 3DG, the 3DG@OMCS electrode exhibit excellent charge/discharge stability and reversibility. Moreover, the desalination behaviour,adsorption kinetics and electrosorption isotherms of the fabricated electrodes investigated by the batch-mode apparatus demonstrates that the 3DG@OMCS electrode has a higher deionization capacity and efficient than the pure OMCS or 3DG. In addition, a comparative study was carried out to explore the electrosorption behavior of 3DG@OMCS from a point view of adsorption kinetics and thermodynamics. The result indicates that the 3DG@OMCS electrode not only own the maximum adsorption capacity, but also it is the monolayer adsorption.