Theoretical Study On The Electrocatalytic Performance Of Two-dimensional Porous Materials For Carbon Dioxide Reduction And Nitrogen Reduction

In recent years,due to the excessive combustion of fossil fuels,the greenhouse gas carbon dioxide content in the air has gradually increased,causing global warming.Therefore,electrochemical reduction of carbon dioxide into high value-added products has been a hot topic in recent years.At the same time,nitrogen is extremely important for the protein synthesis of humans,animals and plants.Nitrogen reduction can convert the abundant nitrogen（N₂）in the air into ammonia（NH₃）.For the two electrocatalytic reactions,whether it is carbon dioxide or nitrogen,the chemical stability of the two is very stable.Therefore,it is very important to seek efficient,clean,high-stability,and selective catalysts.In this article,we are mainly based on two-dimensional porous materials.Research on two kinds of reactions as catalysts.（1）Electrochemical reduction of carbon dioxide（CO₂ER）to highenergy-density multicarbon products is a quite promising technique for large-scale renewable energy storage,for which searching for stable,inexpensive,and efficient catalysts is a key scientific issue.In this work,the potential of an experimentally available single iron（Fe）atom supported on graphdiyne（Fe/GDY）as the CO₂ER catalyst was explored by means of density functional theory（DFT）computations.Our results revealed that Fe/GDY exhibits high stability due to the strong hybridization between the Fe 3d orbitals and the C 2p orbitals of GDY.Interestingly,due to the small limiting potential of-0.43 V,the anchored Fe atom can effectively reduce CO₂to CH₄along the following pathway:CO₂→HCOO^*→HCOOH^*→HCO^*→H₂CO^*→H₃CO^*→O^*+CH₄→OH^*→H₂O,in which the hydrogenation of HCOOH^*to HCO^*is the potential-determining step.Furthermore,the unsaturated HCO^*species on Fe/GDY can provide an active site for further coupling with CO to generate C₂H₅OH with a small activation energy for C-C coupling.Our theoretical results not only propose a new approach to CO₂ER to C₂products on a single-site catalyst but also further widen the potential applications of GDY.（2）The electrochemical reduction of nitrogen（NRR）at ambient conditions is an appealing alternative to the industrial method for ammonia synthesis that requires high temperature and pressure,but its efficiency is greatly dependent on stable and efficient electrocatalysts.Hence,by means of comprehensive density functional theory（DFT）computations,we investigated the potential of a new class of metal-organic frameworks（MOFs）-based catalyst for the NRR,namely,the synthesizedπ-conjugated metal bis（dithiolene）nanosheet（MC₄S₄,M=Fe,Co,Ni,Ru,Rh,Pd,Pt,Os,and Ir）.Our results demonstrated that the NRR catalytic activity of MC₄S₄is highly dependent on the central metal atom.Due to the low overpotential（0.31 V）,the Os C₄S₄nanosheet is predicted to exhibit outstanding NRR catalytic activity through the distal mechanism,in which the hydrogenation of the activated N₂molecule to the N₂H^*species is identified as the potential-determining step.Our work is the first report of 2D MOFs-based electrocatalyst for N₂reduction,opening a new avenue for advancing sustainable NH₃synthesis under ambient conditions.