2D Single And Double Atom Catalysts For Nitrogen Reduction Reaction: A DFT Perspective

Ammonia（NH₃）is a very important chemical product in industrial production.At present,the industrial synthesis of NH₃ needs to consume a lot of fossil energy,which not only aggravates the global energy shortage,but also brings serious environmental pollution problems.In contrast,electrochemical nitrogen reduction（NRR）is a quite promising strategy for NH₃ synthesis.NRR can be carried out within mild condition and simple reactor,and the appropriate catalyst can further reduce the energy consumption.NRR electrocatalyst with higher catalytic activity and better catalytic selectivity can reduce the reliance on fossil energy on the NH₃ synthesis process.Therefore,the development of efficient NRR electrocatalyst has become one of the most important research directions in the field of catalysis.Two dimensional materials are materials with a dimension at the nanometer level.Affected by the quantum size effect,two dimensional materials exhibit unique electronic,optical,and magnetic properties,which often makes them have good performance in the field of catalysis.For example,graphene,molybdenum disulfide（MoS₂）,g-C₃N₄ and other two-dimensional materials show good performance in many electrocatalytic reactions.However,when most two dimensional materials are used as NRR catalysts,solving the catalytic activity and selectivity of the catalysts is still a significant challenge.In order to solve the above problems,the NRR catalytic performance of single transition metal atom catalysts anchored by blue phosphorus and double Fe atom catalysts supported by transition metal sulfides have been explored in this article.Calculation reveals that the two catalysts both have excellent catalytic activity and high selectivity.The main content of this article can be divided into the following two parts:（1）Using density functional theory（DFT）calculations,this work systematically screened the capacity of representative transition metal-N₃（TM-N₃,TM=Sc-Zn,Mo,Ru,Rh,Pd,Ag,and W）centers supported on blue phosphorus（TM-N₃@β-P）as NRR catalysts.The calculation results show that W-N₃ center supported on blue phosphorus（W-N₃@β-P）exhibits excellent catalytic performance with an ultra-low limiting potential of-0.02 V,while the competitive hydrogen evolution reaction（HER）is able to be suppressed on this catalyst.The excellent performance is chiefly caused by the fact that the active sites of the catalyst exhibit a good hybrid with nitrogen when nitrogen is adsorbed in catalyst,and each part of the catalytic system has excellent charge transfer ability in the catalytic process.（2）Based on DFT calculation,the double Fe atom catalysts supported on transition metal sulfides were systematically studied（2Fe@MS₂,M=V,Nb,Ta,Cr,Mo,and W）.The calculation results show that 2Fe@NbS₂ has the best NRR catalytic performance because it has the lowest limit potential（-0.38 V）.By comparing the free energy of adsorbed N₂ molecules and H atom and the potential between NRR and HER,it can be seen that 2Fe@NbS₂,2Fe@WS₂,and 2Fe@CrS₂ have high NRR selectivity.This work shows that double Fe atom supported on transition metal sulfides has excellent NRR catalytic performance.