First-Principles Study Of Electrocatalytic NO And CO Reduction Based On MoSi₂N₄ Monolayer

Using clean electric energy to drive the electrochemical reduction reaction of NO and CO to produce various valuable fuels can optimize the energy consumption structure.Finding suitable electrocatalyst is the key to improve the rate of NO/CO electrochemical reduction.Single-atom catalysts（SACs）have been attracted widespread attention owing to their high atomic utilization.However,the isolated metal atoms on the substrate are inclined to assemble owing to their high surface energy,resulting in low activity or even inactivation.Therefore,it is of great significance to search for an appropriate substrate to strengthen the interaction between TM and the substrate.Recently,MoSi₂N₄（labelled as MSN）,a novel two-dimensional semiconductor material,has been synthesized through the chemical vapor deposition（CVD）method and exhibits superior carrier mobility,mechanical strength and thermal stability over MoS2,which is suitable for the substrate of SACs and expected to have a broad application prospect in the field of electrocatalysis.Therefore,herein,NO/CO electrocatalytic reduction performance of SACs based on MSN monolayer（labelled as TM-MSN）was studied via firstprinciples calculation.The main research contents and results are as follows:（1）The catalytic performances of NO electrochemical reduction reaction（NOER）of TMMSN monolayers were investigated.Firstly,the binding energy,cohesion energy,dissolution potential and kinetic simulation and density of states were utilizied to evaluate the stability and electronic properties of TM-MSN in order to selected the optimal system with high stability and good conductivity.Then,catalysts with high activity were selected according to the Gibbs free energy barrier of NOER.Finally,the selectivity of the selected catalysts was evaluated by analyzing the competitive reaction of NOER.These results clearly indicate that all considered TM-MSN monolayers have excellent electrochemical and kinetic stabilities.In addition,the introduction of TM reduces the band gap,which enhances relatively the electrical conductivity.The introduction of Zr,Pd,Pt,Mn,Au or Mo can greatly improve the NOER catalytic performance of MSN.Among them,Zr-MSN and Pt-MSN showed the best NOER catalytic performance at low concentration of NO with limiting potentials of 0 V and-0.10 V,respectively.（2）The catalytic performance of CO electrochemical reduction reaction（CORR）of CuMSN was investigated.According to the study of（1）,the introduction of Cu atom can activate adjacent three nearby N atomic sites,and these activated N sites are very likely to adsorb multiple CO molecules at the same time,which is conducive to the C-C coupling and electrochemical reduction of CO into valuable C2+ products.Therefore,we continued to explore the CORR performance of Cu-MSN.Firstly,the adsorption capacity of CO and the possibility of C-C coupling were evaluated.Then,the catalytic activity and selectivity of Cu-MSN to CORR were investigated according to the Gibbs free energy barrier.These calculated results show that the three active N sites near the Cu atom can effectively promote the C-C coupling,two CO molecules can be directly coupled after adsorption,and the coupling energy barrier of three CO molecules is only 0.04 e V.According to the Gibbs free energy,the main products of CO reduction are CH4,C2H4,C2H6,C2H5 OH and C3H7 OH.The calculated Gibbs free energy barriers are all lower than 0.57 e V,indicating the excellent catalytic activity of Cu-MSN in CORR.In addition,the limiting potential difference UL（CO）-UL（H2）between CORR and HER is close to 1 V,which demonstrats that the Cu-MSN catalyst has a high selectivity for CORR.