Theoretical Study Of Transition Metal Atoms Doped Two-dimensional TAP And EPc Materials For Ammonia Synthesis From Electrocatalytic Nitrogen Reduction

Ammonia（NH₃）synthesis is critical to the stability of the Earth’s ecosystems.Electrocatalytic nitrogen reduction has attractive potential and wide application prospects in the synthesis of ammonia,but there are challenges such as low reaction efficiency and poor selectivity,so it is particularly important to find stable and efficient electrocatalysts.Based on the density functional theory and high-throughput screening,the catalytic performance and structural-activity relationship of two-dimensional single atom catalysts（SACs）TM@TAP and double atom catalysts（DACs）TM₂@EPc in nitrogen reduction reaction（NRR）are systematically investigated in this paper.The main research contents and results are as follows:1.The transition metal（TM）atoms of 3d（Sc–Zn）and 4d（Y–Cd）series are doped into the central vacancy of the chemically modified two-dimensional tetraazaporphyrin（TAP）monolayer material,forming 20 kinds of single atom catalysts（TM@TAP）.The pathway and micro-mechanism of nitrogen reduction reaction under the catalysis of TM@TAP are systematically studied by the density functional theory.The results show that the four kinds of catalysts TM@TAP materials（TMs are Nb,Zr,Ti and Mo,respectively）exhibit good catalytic activity.The side reaction of hydrogen evolution reaction（HER）is calculated and analyzed,we discover that these catalysts show higher selectivity for nitrogen reduction reaction.Among them,the catalytic effect of Nb@TAP material is the best,the nitrogen reduction has the lowest onset potential(|U_onset|)（0.43 V）by enzymatic mechanism.This work provides a good candidate material for electrocatalytic nitrogen reduction reaction,and provides valuable clues and evidence for the design of stable and efficient single atom catalysts.2.The arbitrary combinations（homo-and hetero-）of two transition metals from3d/4d/5d series（totally 30）are doped into the two-dimensional expanded phthalocyanine（EPc）monolayer material to form the double atom catalysts（TM₂@EPc）.Through high-throughput screening step by step,we discover a large class of highly efficient and stable electrocatalysts TM₂@EPc for nitrogen reduction reaction.Among them,there are 32kinds of materials with|U_onset|below 0.4 V.Surprisingly,we find that four nitrogen reduction reaction pathways（（V,Mo）-best pathway-1,（V,Mo）-best pathway-2,（V,W）-best pathway,（Nb,Mo）-best pathway）under the catalysis of three catalysts（（V,Mo）,（V,W）and（Nb,Mo））can be carried out spontaneously.In these four pathways,theΔG of all protonation steps are less than zero and don’t need any energy input,these are rare.And this discovery has important guiding significance for the rational design of high-efficiency nitrogen reduction electrocatalysts.In addition,based on the analysis and summary of a large number of data three simple and effective descriptors(Q_*N2,BOP_*N2and L_*N2)are proposed,which provides the new method and idea for screening electrocatalysts with excellent performance,rapidly and efficiently.