Study Of Ambient Stability And Electrocatalytic Properties Based On The Electronic State Regulation Of Two-dimensional Black Phosphorus

Two-dimensional?2D?black phosphorus?BP?is currently,besides graphene and antimonene,the only single-element 2D material that can be obtained by mechanical stripping.Since 2014,when it was first stripped from its bulk materials,it has attracted widespread attention.As a p-type semiconductor,the unique anisotropy,adjustable direct bandgap structure and high carrier mobility of black phosphorus make it stand out from the other 2D materials.However,the stability of few-layered black phosphorus is quite bad due to the existence of active lone-pairs of phosphorus atoms,and the severe degradation under environmental condition seriously hindered its further development and research in practical application.Therefore,the key to the stabilization of black phosphorus is to understand the nature of its degradation and put forward the protection method from the perspective of degradation mechanism.In addition,current research on the nature of black phosphorus degradation is based on how to inhibit the activity of the active lone-pairs,and little work has been done on how to use these lone-pairs to regulate the electronic structure of black phosphorus.This thesis mainly focused on the active lone-pairs of phosphorus atoms.Firstly,from the perspective of inorganic chemistry,it was devoted to improving the stability of few-layered black phosphorus under environmental conditions.Secondly,by regulating the electronic state and energy band structure of black phosphorus matrix composites,the structure-activity relationship between these factors and the electro-catalytic performance was explored,and the following research achievements have been made:1.A strategy of surface functionalization to protect 2D black phosphorus material was developed with inorganic small molecule H₃BO₃ by simple mechanical ball milling.XPS characterization confirmed that the electron deficiency of H₃BO₃molecular can coordinate with the active lone-pairs of phosphorus atoms,resulting in the formation of P-O?B.The coordination bond of P-O?B can effectively avoid the hydrogen-bond interaction between the bonded O and water molecules,thus inhibiting water molecules to draw the P atoms from the surface of black phosphorus and ultimately protect the top layer of black phosphorus from degradation,which improved the environmental stability of black phosphorus.Taking the degradation mechanism into consideration,we revealed the formation mechanism of P-O?B coordination bond,and found that H₃BO₃ small molecules on the surface of black phosphorus would not damage its original crystal structure,so as to maintain its unique properties.In this part,from the perspective of inorganic chemistry,this strategy to improve the environmental stability of black phosphorus materials is realized in essence,and we hope this can provide reference to enrich the choice of the chemical surface functionalization for black phosphorus.2.On the basis of 2D black phosphorus nanosheets,metal cobalt nanoparticles were in situ grown on its surface by solven thermal reduction,and the nanocomposite Co/BP was obtained.Moreover,a metal-semiconductor schottky junction was constructed,and the energy band and electronic state structure of the composite are regulated by the difference of different constituents'work functions.Ultraviolet photoelectron spectroscopy?UPS?tests showed that the Fermi level of black phosphorus nanosheets is higher than that of cobalt nanoparticles.In order to achieve the balance of Fermi level,electrons would migrate from black phosphorus to metal cobalt nanoparticles.On the one hand,the electrons migration would change the energy band and electronic structure of composite materials,and thus promoting their catalytic performance as an oxygen evolution reaction?OER?catalyst.On the other hand,the effective migration of electrons from black phosphorus would inhibit its degradation,thereby achieving stable electrocatalytic activity and thus demonstrating excellent OER activity and good stability,which is comparable to that of commercial IrO₂.In this part,the metal-semiconductor schottky junction was skillfully constructed in Co/BP composite,and the structure-activity relationship between electronic structure and catalytic performance was revealed.3.High performance composite catalyst with electronic state regulation was designed based on the unique electronic structure of 2D black phosphorus.Co₃O₄with mixed valence state(Co²⁺and Co³⁺)was selected,and a black phosphorus modified Co₃O₄ composite material Co₃O₄@BP was synthesized by simple ultrasonic treatment.The relative content ratio of Co²⁺and Co³⁺(Co²⁺/Co³⁺)in Co₃O₄@BP was compared with that in ultrasonic treated pure Co₃O₄,and the electronic structure of the composite Co₃O₄@BP and the single phase including black phosphorus nanosheets and Co₃O₄ nanoparticles was also explored.It was found that although the active lone pairs are a fatal shortcoming for the stability of the pure 2D black phosphorus as an electrocatalyst,the unique electronic structure of black phosphorus can be fully utilized in the composite Co₃O₄@BP to achieve the regulation of the whole electronic state of the composite.The regulation of electronic state in Co₃O₄@BP could not only improve the relative proportion of Co²⁺/Co³⁺,producing a large number of active sites with Co²⁺to improve OER performance,but also effectively inhibit the degradation of black phosphorus.The composite in this part complemented the advantages of the two constituents and innovated their electronic structure,which can provide a new perspective for the design of efficient OER electrocatalysts.In this paper,mechanical ball milling,solvent thermal reduction and ultrasonic assisted synthesis were used.By making full use of the active lone pairs which are the fatal defect of 2D black phosphorus,the environmental stability of black phosphorus was significantly improved.The black phosphorus matrix composites were constructed,and the relationship between the electronic structure and the electrocatalytic performance of the composite materials was deeply explored,so as to provide some experience for the efficient use of the unique electronic structure of 2D black phosphorus in the future.