Theoretical Study Of CO₂ Hydrogenation On Cu Surfaces

With the development of modern society and industry,the carbon dioxide content in the atmosphere continues to rise,and the greenhouse effect is more serious.The importance of the reduction reaction of carbon dioxide has begun to pay attention to.The reaction has two most important advantages:the reduction reaction of carbon dioxide can significantly reduce the content of carbon dioxide in the atmosphere to improve the increasingly serious greenhouse effect;Free carbon in the atmosphere is fixed so that carbon can be fully industrially recycled and the industrial utilization of carbon can be improved.Therefore,the reduction reaction of carbon dioxide has received a lot of attention in chemical engineering and green chemistry.For carbon dioxide reduction reactions,common catalysts include many types,such as:transition metals?Cu,Ni,etc.?,metal oxides?Zn O,Al₂O₃,etc.?,alloys?Cu Zn,etc.?etc..Among them,metal copper,as an important industrial catalyst,has been widely studied for its low price and high catalytic efficiency.However,most of the previous studies focused on the thermodynamically stable Cu?111?surface,while the research on other low-index surfaces involves less.Therefore,this work uses density functional theory to simulate the reaction process of carbon dioxide hydrogenation reduction on three low-index copper surfaces.This work mainly studies the production of C1 product methanol and possible by-product methane by hydrogenation of CO₂.In this work,all possible reactants,intermediates and products Cu?111?,Cu?100?,and Cu?110?for the production of methanol and methane from carbon dioxide were simulated,and most intermediate products were found.The adsorption performance on Cu?100?and Cu?110?surfaces is better than that of intermediates on Cu?111?surface.In addition,all possible reaction paths for the formation of methanol and methane on different copper surfaces are discussed in detail in this paper based on the adsorption energy of all reactants,intermediates and products.The results show that the reaction of CO₂hydrogenation to methanol preferentially adopts the formate path containing the intermediate HCOOH*on the three low-index surfaces of copper,while the carboxylate path requires the most heat and is not conducive to the reaction.In addition,the methanol formation reaction has lower endothermic energy on the Cu?100?and Cu?110?surfaces than the Cu?111?surface,and has better catalytic activity.On the copper surface,the reaction of CO₂reduction to produce methane as a by-product preferentially chooses the reverse water gas and carbon monoxide hydrogenation reaction path,followed by the formate path.The carboxylate path has a higher endothermic reaction energy,which is not conducive to the reduction reaction.The reaction of carbon dioxide reduction to form methane requires less thermal energy provided by the environment on the Cu?100?and Cu?110?surfaces,and the ability to catalyze methane production is better.