Application Of Two-dimensional Materials Such As Graphene And Phosphorene In The Field Of Energy Conversion

With the development of human society,energy and environment are facing a double cri-sis.Energy is the guarantee of the further development of human society,and environment is the foundation of human survival.Therefore,the key to solve the current energy and environ-mental problems is to find clean energy and change the way of energy use.Fuel cell is a clean and pollution-free energy conversion equipment with high energy conversion efficiency.The cathode materials of traditional fuel cells are all Pt based precious metals.Because Pt based precious metals are expensive and scarce in resources,and their durability is poor,finding new electrode materials of fuel cells is the key to solve the current dilemma of fuel cells.Recent experimental and theoretical studies have shown that the noble metal atom loaded on a new two-dimensional material as the electrode material of fuel cell has very good performance.In this paper,the performance of black phosphorus as cathode material of fuel cell and the relationship between the activity of oxygen molecules on Pt doped graphene and the applied electric field are studied based on density functional theory.The research results are as follows:1.The adsorption characteristics of intermediate products on the surface of black phospho-rus and several oxidation-reduction mechanisms on black phosphorus were studied.The results show that the adsorption of H on black phosphorus surface is easier than that of O₂on black phosphorus surface,and ooh is formed spontaneously by the adsorbed h and O₂.Further hydro-genation of OOH to hooh may lead to the formation of OH and H₂O,and further hydrogenation of Oh may lead to the formation of a second H₂O.The speed limit step of the whole reaction is1.02 e V.In addition,the proposed kinetic process is confirmed by Gibbs free energy calculation and thermodynamic simulation.These results indicate that as one of the new two-dimensional materials,phosphine may be a promising nonmetal cathode material for PEMFC.2.The interaction between oxygen molecules and graphite based nanomaterials plays an important role in gas storage,sensors,catalysts and other fields.We studied the effect of external electric field on the interaction between O₂and Pt doped graphene(Pt/graphene)substrate by DFT calculation.It is found that under the action of positive electric field,O₂moves over Pt atom,the adsorption energy of O₂on Pt/raphene substrate increases,and the bond length of O₂becomes longer.Under the action of negative electric field,this phenomenon is opposite.Next,we study the cause of this effect from the electronic structure level,and find that the applied electric field can adjust the amount of charge transferred to O₂,and the amount of charge transferred to O₂mainly occupies the initial vacancy of O₂?p*orbital,and the amount of charge on the anti bond orbital of oxygen molecule can affect the activity of O₂.3.As new clean energy will eventually be converted into electric energy,lithium-ion battery as a storage device for electric energy has been developed quite mature,but due to the lack of lithium resources,it will seriously hinder the storage and use of electric energy.In the last part of this paper,sodium ion battery as a substitute of lithium-ion battery is discussed through cooperation with experiments.In addition,the properties of p-doped double-layer graphene and n-doped graphene and MoS₂ as electrodes of sodium ion batteries were studied.