First Principle Study On The Mechanism Of Bilayer Tetragonal AlN Electrochemical Energy Storage

In the field of electrocatalysis,electrode materials should have the following characteristics.Firstly,high conductivity,because the reaction process requires an electric field to affect the energy of lithium or hydrogen.The electric field and electrons will not be effectively transferred if the conductivity of the materials is low.Second,high specific surface area,only materials with a high specific surface area can expose more attachment sites,and can better attach molecules such as lithium,oxygen,hydrogen,organic molecules,carbon dioxide to participate in the reaction.The last is high void fraction,this characteristic helps to successfully penetrate small molecules such as oxygen and carbon dioxide into the materials to participate the reaction.If there are not enough voids,small molecules will not penetrate the material in contact with the electrolyte and thus hinder the reaction.Two dimensional materials possess the advantages of high specific surface area,high porosity and conducive to ion attachment and oxygen transport.Carbon-based materials,represented by graphene,when used as a positive electrode catalyst,although having good catalytic effect,is prone to undergo unwanted side reactions with electrolyte or oxygen,leading to unstable properties.Therefore,carbon based two-dimensional materials are not good catalysts.In this paper,we proposed bilayered tetragonal AlN as an alternative to carbon based two-dimensional materials,as this material belongs to group III-V materials and has similar properties to group IV C.Also,the nitrogen and aluminum elements are relatively close to the carbon elements in the periodic table.In this paper,AlN is simulated using First Principal Density Functional Theory(DFT),and a solution using bilayer tetragonal AlN as catalyst is presented.Lithium-air batteries store and release energy through the reaction between lithium and oxygen.The discharge behavior induced by the dissociation of O and the absorption of lithium is studied as well.The intermediate products of LiO or 2(LiO)and their nucleation paths are calculated,and a free energy diagram is further generated to predict the discharge products stimulated by LiO.Finally,the expected discharge overpotential is 0.57 V and the charged overpotential is 0.21 V.The activation barrier for LiO catalytic decomposition during charging is then predicted to be 1.45 e V.Based on the above results and combined with electronic analysis,it is known that bilayer tetragonal AlN is a promising catalyst for lithium air batteries.Subsequently,the effect of AlN on catalyzing the generation of organic compounds from CO was predicted.It is found that the hydrogen evolution reaction on AlN requires an additional energy of 1.83 e V,which can effectively inhibit the generation of hydrogen,also AlN can absorb and activate CO.We found that CH OH is formed during CRR at an external voltage of 1.59 to 1.70 V.When the external voltage is 1.70～1.83 V,the CRR process will not only form CH OH,but also CH.Although CRR on AlN requires a higher voltage,the lower price and the larger voltage range still indicate that AlN is an effective catalyst for the electrocatalytic reduction of carbon dioxide.