Amine-assisted Exfoliation Of Metal Phosphorus Trichalcogenides And Their Application For Electrocatalysis

The preparation and structure engineering of two-dimensional(2D)materials have been the focus of nanomaterial research recently.Two-dimensional materials are kinds of materials which are thinned down to the atomic limit.At the present day,it is known to us that there are tremendous types of 2D materials including graphen,black phosphorus,transition metal dichalcogenides(TMDs),metal phosphorus trichalcogenides(MPX3)and so on.Many universal methods are proposed for preparation of these 2D materials like mechanical exfoliation,lithium intercalation,liquid sonication exfoliation,chemical vapor deposition(CVD)methods and so on.However,due to the distinction between various materials,the result of one method applied to different materials could vary a lot.Different methods also have certain scope of application,so trying different methods for various materials is conducive to the development of new and efficient preparation methods.Two-dimensional materials usually exhibit different physical and chemical properties compared with their bulk counterparts because such materials in a certain dimension is reduced to the atomic limit and electrons are confined to two dimensions,making them promising for a wide range of unique applications including catalysis,electronics and optoelectronics,sensors,energy storage and conversion and so on.In addition,The high specific surface area of two-dimensional materials with more exposed active sites and surface atoms makes their surface highly controllable,so they are very suitable to be used as templates for structural engineering to explore and optimize their unique properties.In this dissertation,FePS3,a typical material from a new kind of layered material MPX3,is chosen as the research object to develop a novel method of amine-assisted liquid phase exfoliation to obtain FePS3 nanosheets,at the same time to achieve directional structure engineering,finally to realize the performance optimization toward electrocatalytic hydrogen evolution reaction.The main contents of this dissertation include the following two points:(1)A new method of amine-assisted exfoliation was developed to exfoliate FePS3.N-propylamine was successfully intercalated into the interlayer of FePS3 by just stirring the mixture at room temperature.Meanwhile,the level of amine intercalation can be regulated by the reaction time.Then ultrasonic exfoliation was conducted to obtain few-layer FePS3 nanosheets with the size of about 1 to 4 pm and the thickness of about 6 nm.The size of part of the nanosheets is over 10 ?m.This method can also be applied to other similar materials like MnPS3.(2)By changing the reaction temperature of the amine intercalation,directional regulation of the metal valance,chemical component and crystallinity of the FePS3 nanosheets can be achieved.With the reaction temperature increasing,the ratio of Fe3+/Fe2+ increased,more sulfur atoms lost,and these nanosheets became more amorphous.It is the combined effect of these factors that regulate the intrinsic electrical conductivity,thus modulating the electrocatalytic hydrogen evolution reaction performance of FePS3 nanosheets.An decrement of overpotential at-10 mA/cm2 of 147 mV and a drop of Tafel slope from 139 mV dec-1 to 94 mV dec-1 were achieved in these nanosheets.