Theoretical Study On The Electrochemical CO₂ Reduction Reaction On Bimetallic M@Cu?211? Single Atom Surface Alloys

At present,the Paris Agreement to curb greenhouse gas emissions such as carbon dioxide?CO₂?has entered into the implementation stage,but the global climate is still facing major challenges.In the process of CO₂ electrochemical reduction reaction?CO₂RR?,high potential is needed to overcome the reaction energy barrier,and the existence of highly competitive hydrogen evolution reaction?HER?on the cathode electrode is considered,which results in low conversion efficiency and poor product selectivity of CO₂RR.In recent decades,the design and development of efficient electrocatalyst that can reduce CO₂ to high value-added fuel has always been a leading research direction in the world.In this dissertation,the first principle density functional theory?DFT?is used to simulate the adsorption of intermediates formed by protonation and reduction of transition metal monoatomic surface alloy M@Cu?211?as model catalyst?M=Y,Fe,Co,Ni,Zn,Ru,Rh,Ag,Au,Pd and Pt?in the process of CO₂ RR.Besides,the reaction mechanism of CO₂RR is deeply explored through the analysis of geometric and electronic effects,and combined with microkinetic modeling,which established a new research idea for the design and selection of high efficiency electrocatalyst.According to the research:?1?M-modified Cu?211?step edge site can be used as the active site of O=C=O inert bond activation,and the calculation results show that M-Cu bimetallic bond has a good adsorption and activation effect on CO₂,which is also consistent with the experimental bimetallic site is the reactive active site.In addition,the calculated dissociation potential shows that the single atom surface alloy M@Cu?211??except M=Y?has a high stability in the strong acid medium with p H=0,and the highly efficient catalysts Ru@Cu?211?and Fe@Cu?211?which produce methane have a high thermal stability under the AIMD condition of 500K.?2?The thermodynamic data show that the main reaction path of the single atom surface alloy CO₂ RR process is determined as*COOH?*CO?*CHO,and the reaction rate control steps are generally*CO+H⁺+e^-?*CHO,so the deep hydrogenation product methane or methanol can be generated under more negative applied voltage.In particular,Fe@Cu?211?and Ru@Cu?211?are considered to be the most effective electrocatalysts for the conversion of CO₂ to CH₄ because they break the internal linear proportion relationship between the key intermediates,and the limit potentials of methane generation are 0.65 e V and 0.44 e V,respectively.In addition,in order to screen out high-efficiency catalysts more efficiently,the binding energy of*CO and*OH is used as descriptors in this dissertation,and conclude that the second metal with both moderate oxophilic and carbophilic is preferred.?3?Five H₂O molecules were embedded on the surface of Cu?211?to form an explicit water model.It was found that the model had excellent adsorption and activation effect on CO₂,which indicated that the model was very close to the real scenario of electrochemical reduction of CO₂.In addition,the results of micro dynamics simulation show that the order of the initial potential of methane formation is Cu?211?<Fe@Cu?211?<Ru@Cu?211?.The results are consistent with those predicted by thermodynamics.Moreover,the initial potential of methane formation on Cu?211?is lower than that from polycrystalline copper electrode,which is also consistent with the result that Cu?211?facet is the active surface of electrocatalytic reduction of CO₂ to methane.