Liquid-Phase Exfoliation Of Zirconium Disulfide Nanosheets And Its Electrocatalytic Performance

Transition metal disulfides have attracted much attention due to their excellent physical and chemical properties.Zirconium disulfide(ZrS₂),one of TMDs in?B group,which owns higher carrier mobility than molybdenum(Mo S₂)at room temperature,has been widely applied in the fabrication of the field effect transistors,sensors and laser fiber.However,the large-scale applications of ZrS₂ have been hindered by the lack of a simple and efficient preparation method for mass production of single or few-layer ZrS₂ nanosheets.Liquid phase exfoliation is considered to be a simple,low cost,large-scale and high yield method to prepare two-dimensional materials.While,there are few studies on the liquid-phase exfoliation of ZrS₂.And in a literaure,the laterial size of ZrS₂nanosheets is small and the preparation process of precursor is very complex.Therefore,it is particularly important to develop a low cost,and green liquid phase exfoliation method with high yield,high quality to preparation ZrS₂ nanosheets.In view of this,three different exfoliating systems,aliphatic amine-N-methylpyrrolidone(NMP),imidimine-ethanol and inmidazolium ionic liquid aqueous solution,were developed to exfoliate ZrS₂ via liquid phase exfoliation,and the single or few-layer ZrS₂ nanosheets with high yield and quality were obtained.The main research contents are as follows:1.Fifteen kinds of aliphatic amines were used as intercalators for the liquid phase exfoliation of ZrS₂ in NMP.The results show that the single or few-layer ZrS₂ nanosheets were successfully prepared and the yield is as high as 27.3%.The thickness of nanosheets was mainly1-2 nm and the laterial size is at micron level.The addition of aliphatic amines had significantly improved the yield of ZrS₂ nanosheets,and the molecular size and intensity of alkalive of the amines have played important roles in the exfoliation of ZrS₂.The study on the exfoliation mechanism shows that the acid-base interaction between the amino group of aliphatic amine and Zr of ZrS₂ promotes the amino group to enter the interlamination of ZrS₂crystal,and expands its interlayer spacing under the action of ultrasonic wave,thus resulting in the stripping of ZrS₂nanosheets.The as-prepared ZrS₂ nanosheets were used in electrocatalytic N₂-to-NH₃ fixation by electrocatalytic nitrogen reduction,and the yield of ammonia was three times higher than that of bulk ZrS₂.2.Using phthalimide as intercalator,few-layer ZrS₂ nanosheets with a high yield of 43.1%were successfully prepared by liquid phase exfoliation in green and low-cost ethanol solvent.It is found that the addition of methyl,hydroxyl and amino groups on phthalimide is not conductive to the exfoliation of ZrS₂ nanosheets.The exfoliating mechanism shows that the interaction between the imide group of phthalimide and ZrS₂ is the main drivig force for the exfoliation of ZrS₂ nanosheets.The system has been applied to the liquid pahse exfoliation of other transition metal disulfides(molybdenum disulfide(Mo S₂),titanium disulfide(Ti S2),tungaten disulfide(WS₂),tantalum disulfide(Ta S₂),molybdenum selenide(Mo Se₂),and tungsten selenide(WSe₂)).The monolayer or few-layer nanosheets with high yield and quality have also been successfully prepared.This suggests that our method has a good universality for the preparation of TMDS nanosheets.3.Six kinds of functionalized ionic liquids were designed and synthesized,such as, 1-tetradecyl-3-methylimidazole-5-methylsalicylic([C₁₄Mim][C₈H₆O₃]),1-tetradecyl-3-methyl imidazolium([C₁₄Mim][CHN₄]),1-tetradecyl-3-methylimidazole hexahydrophthalimide([C₁₄Mim][C₈H₁₀NO₄]),1-tetradecyl-3-methylimidazole-1,2,4-triazole([C₁₄Mim][C₂H₂N₃]),1-tetradecyl-3-methylimidazole benzoic acid([C₁₄Mim][C₇H₅O₂])and 1-tetradecyl-3-methyl imidazole-1H-benzotriazole([C₁₄mim][C₆H₄N₃])and their aqueous solutions were used in the liquid phase exfoliation of ZrS₂.For the first time,ZrS₂ nanosheets with high yield(82.85%)and high quality were prepared in ionic liquid aqueous solution.The basic and molecular size of the anions in ionic liquids had important effects on the exfoliated yield of ZrS₂ nanosheets during this process.Additionally,the Zeta potential of ZrS₂ nanosheets dispersions were all above 30 m V,which present good stability.The prepared ZrS₂ nanosheets had been used in the electrocatalytic hydrogen evolution reaction.Compared with that of the bulk materials,ZrS₂ nanosheets show higher electrocatalytic performance.