DFT Study On The Performance And Mechanism Of Copper-Based Catalysts To Catalyze CO₂ To Methanol

The promise of CO₂ hydrogenation to synthesize methanol（CH₃OH）could reduce the greenhouse effect and alleviate the energy crisis.Cu group and its oxide catalyst are the most widely used catalysts in methanol production.Metal Pd is often doped with Cu group catalyst to improve reaction efficiency.However,due to limitations of conventional experiments,the researchers were not able to fully verify the hydrogenation mechanism for the synthesis of CH₃OH.Simulations based on density functional theory（DFT）are currently one of the main methods for studying the mechanism of the CO₂hydrogenation of CH₃OH.In this paper,Reverse water gas transformation（RWGS）mechanism of CO₂ hydrogenation on Cu-based catalyst for methanol is studied by DFT.By calculating the surface energy of several commonly used Cu catalysts,the most stable Cu（111）surface was selected for the energy optimization of the constructed reactive intermediates.The energy of the optimized intermediates was significantly reduced and the structure stabilized.On this basis,the surface catalytic models of Cu（111）and CuO（111）were constructed to determine the stable adsorption configuration,adsorption position and adsorption energy of the related intermediates on both surfaces.The reaction energy and the barrier of the reaction of each substrate under the RWGS pathway were calculated,and the velocity limit analysis of the total synthesis pathway map was performed.The results show that on the surface of Cu（111）and CuO（111）,most of the intermediates show the law of adsorption energy Cu（111）>CuO（111）,and the activation barrier of CuO（111）is relatively higher than that of Cu（111）,and the surface of Cu（111）has better catalytic performance.The surface models of Cu₆Pd₃（111）,Cu₃Pd₆（111）and Cu Pd WL（111）（whole layer doping）were constructed by doping metal Pd on the surface of Cu（111）,respectively,and the catalytic properties and reaction mechanism of the reactive species in the Cu-Pd bimetallic catalyst were further explored.The results show that the doping of Pd atoms changes the adsorption configuration,adsorption site and corresponding adsorption energy of intermediate molecules,and for intermediates such as COOH*,CO*,HCO*,H₂CO*,CH₃OH*,H*,H₂O*,the adsorption energy increases with the increase of Pd doping ratio,showing the adsorption effect of Cu Pd WL（111）>Cu₃Pd₆（111）>Cu₆Pd₃（111）,of which the adsorption effect on the surface of Cu Pd WL（111）is the most stable.In the synthesis reactions such as CO₂*dissociation,H₂O formation,CO*hydrogenation to HCO*,HCO*to H₂CO*,and H₃CO to methanol,the addition of Pd reduced the activation barrier of the reaction,of which the effect on the surface of Cu Pd WL（111）is the most obvious,and the complete reaction path of CH₃OH synthesis is easier to achieve,which is consistent with the literature showing that Cu-Pd bimetallic catalyst has a strong synergistic effect on CO₂ hydrogenation to CH₃OH.