Preparation,stability And Applications Of Two-Dimensional Black Phosphorus

In recent years,two-dimensional materials have attracted widespread attention and research,and play a huge role in various fields of application.Among them,due to unique two-dimensional fold plane structure,adjustable energy band structure(0.32.0 eV),carrier mobility up to 1000 cm2 v-1 s-1 and anisotropy,black phosphorus has been extensively and deeply studied by researchers in recent years,and has been applied in field effect transistors,photoelectric conversion devices,energy storage,and photocatalysis,and has shown broad application prospects.However,to achieve a wider and more advantageous application,efficient and scalable preparation of black phosphorus nanosheet is essential.At the same time,the chemical stability of black phosphorus is poor,it is also important to study the chemical process of black phosphorus degradation in depth and propose the means to stabilize black phosphorus from the perspective of degradation mechanism.In addition,it has not been long’(5 years)to deeply study black phosphorus,and application of black phosphorus in other aspects is worth further study and exploration.This paper mainly focuses on the preparation,basic property research and application exploration of black phosphorus,and includes the following aspects:(1)A method for preparing black phosphorus nanosheet by shear exfoliation in liquids was developed,and stable storage of black phosphorus nanosheet for a long time was realized.Micron-sized black phosphorus nanosheet and black phosphorus nanosheet dispersions were prepared by high-speed shear exfoliation.The shear exfoliation process was studied in three solvents:ethanol,acetone and N,N-dimethylformamide.The influence of the parameters on the concentration of black phosphorus nanosheet was studied,and the relationship between these parameters and concentration of black phosphorus nanosheet was obtained.It was found that the exfoliation efficiency of black phosphorus in acetone was the highest.By tracking the stability of the black phosphorus nanosheet in these three solvents,it was found that the black phosphorus nanosheet could maintain stable for a long time(20 days)when dispersed in acetone in dark.Finally,we prepared a liter of black phosphorus nanosheet dispersion solution in acetone,and achieved the stable preservation of black phosphorus nanosheet in acetone for several months.(2)Revealed the degradation chemical process of black phosphorus in water,and achieved the long-term maintenance of structure and function of black phosphorus nanosheet in water.By tracking the changes of black phosphorus and ions in water,the degradation products of black phosphorus were determined,mainly as PO23-,PO33-and PO43-.Combined with theoretical calculations,oxygen is the key factor for the degradation of black phosphorus.The morphological changes of black phosphorus nanosheet in water were traced during its degradation,and it was found that the degradation of black phosphorus in water occurred preferentially at the edge P atoms.By further analyzing the degradation products of black phosphorus,it is determined that the degradation of black phosphorus in water conforms to the characteristics of quasi-first order parallel reaction,and the reaction kinetic constants of the products PO23-,PO33-and PO43-are 0.019,0.034 and 0.023 day-1,respectively.Finally,the structure of the black phosphorus nanosheet was stable for several months in water by simple deoxygenation treatment.Combined with the highly e:fficient photocatalytic hydrogen production activity of black phosphorus,it was verified that black phosphorus could also maintain its photocatalytic hydrogen production function for a long time without oxygen.(3)Discovered and further explored the performance and advantages of black phosphorus in flame retardant application,and determined that black phosphorus can play an efficient flame retardant effect in polymers with different thermal stability.Through the direct comparison of the improvement of flame retardant properties of cellulose and polyacrylonitrile with black phosphorus,red phosphorus and triphenyl phosphate,it is found that under the same or even lower additive amount,black phosphorus can improve their flame retardant properties more effectively,the efficiency is 2 times and 4.4 times of red phosphorus and triphenyl phosphate respectively.Through the analysis of combustion products and thermal analysis,it is found that the efficient flame retardant of black phosphorus mainly comes from its advantage in the two-dimensional structure during solid phase reaction.It can promote the formation of uniform,continuous and heat stable carbon layer at the interface during the combustion,and block the heat and mass transfer of combustion reaction,thus stopping the combustion.In addition,black phosphorus can improve the flame retardant performance of polyacrylonitrile and enhance its mechanical properties.