Benzidine And Protonated Carbon Nitride Organic Functionalized Graphene-based Electrode With High Adsorption Performance For Capacitive Deionization Devices

Capacitive deionization?CDI?is an emerging desalination technology that removes charged ions from aqueous solution based on the principle of an electric double-layer?EDL?,and which have the advantages of low cost,low voltages?<2 V?,no secondary pollution,and environmental friendliness.Electrode materials are critical to the performance of CDI technology.As a robust two-dimensional material,graphene,a honeycomb crystal lattice that is arranged by one-atom-thick sheets of sp²-bonded carbon atoms,has many fascinating chemical and physical properties,such as excellent electrical conductivity?⁷200 S/m?,large specific surface area?theoretical value 2630 m²/g?and high adsorption capacity.During its preparation process,graphene-based materials tend to reformulate agglomerates and micropores because of the?-?interactions between graphene sheets.This makes it difficult for salt ions to obtain access to the inner layers of stacked graphene to form an EDL or leads to the overlapping of the EDL in micropores.To inhibit the aggregation of graphene,many researchers use small molecules to open agglomerated graphene.In this paper,graphene oxide composites were synthesized using organic synthesis techniques.First,the optimum temperature for the reaction of benzidine?DAB?and p-phenylenediamine?PDA?with GO was investigated.Secondly,the optimal ratio of carbon monoxide?C₃N₄?to GO is studied.The results show that:?1?The optimum temperature for the reaction between DAB and GO is 130°C,and the optimum temperature for the reaction between PDA and GO is 100°C.The specific capacitance of DAB-mGO₁₃₀ is larger than that of PDA-mGO₁₀₀.The adsorption capacity of DAB-mGO₁₃₀ symmetric electrodes in Ca²⁺,Mg²⁺,Na⁺solution is 13.55,8.02,7.88 mg/g,respectively,which were 1.3,1.3 and 1.6 times higher than adsorption capacity of AC symmetric electrodes.?2?The optimum ratio of C₃N₄to GO reaction is 1:8.The H-C₃N₄-mGO_1/8 has a larger specific capacitance than g-C₃N₄-mGO_1/8.Due to the excessive lone pair of electrons at the exposed portion of H-C₃N₄,it is repulsive with the negative ions in the solution,thus forming an asymmetric CDI electrode with AC.The adsorption capacity of the asymmetric electrode in NaNO₂ solution was 12.71mg/g.