Single-atom Catalyst Supported On Copper Surface For CO₂ Electroreduction:a Computational Study

Due to the global consumption of fossil fuels,man-made CO₂emissions are increasing,which has caused deep concern about global warming.The use of renewable energy,that is,the reduction of CO₂through electrochemistry（EC）,and the conversion of CO₂into high value-added fuels and chemicals,can play an important role in global efforts to meet current energy demand and climate challenges.In the past two decades,various experimental approaches,including photocatalytic,thermocatalytic,and electrocatalytic techniques,have made remarkable achievements in the study of CO₂reduction reaction（CO₂RR）.Among them,electrocatalysis,which can store energy in the form of chemical bonds and convert carbon dioxide into high value-added chemicals and fuels,has attracted much attention.Combining catalyst and electrolyte design and catalytic mechanism to provide scientific insights is the key to promoting this technology to industrial applications.The thermodynamic redox potentials of different products of CO₂RR are close,resulting in poor selectivity for specific products.It is well known that the thermodynamic redox potentials of different CO₂RR products are similar,resulting in poor selectivity of most reported electrocatalysts.Therefore,developing low-energy-consumption,high-selectivity catalysts to reduce CO₂to more attractive C₁and C₂products such as alkanes,alkenes,and alcohols is still a challenging task.Although many electrocatalysts have been reported,copper（Cu）is by far the most promising catalyst for the conversion of CO₂to C₁and C₂products.In the study of CO₂RR.In this paper,the density functional theory（DFT）calculation method was used to explore the reaction mechanism of transition metal supported copper-based single-atom alloys for catalytic reduction of CO₂to C₁and C₂products.It focuses on its electronic structure and optimal reaction path,and explains the detailed process of C-C coupling.The specific research contents include the following two aspects:（1）In current study,11 transition metal-supported single-atom catalysts were selected,and the optimal single-atom catalysts were screened by their CO adsorption energy to achieve the reduction of CO₂to C₁products.In CO₂RR,The step of*CO₂→*COOH→*CO is the key step of the C₁pathway in the current study,so we compared the energy barriers of 9 catalysts in this step,and then screened out two that can reduce CO₂to C₁products,the optimal catalysts Co@Cu（111）and Ir@Cu（111）.The reaction mechanism of CO₂reduction over two catalysts,which reduce CO₂to methane via different pathways,is investigated in detail.We also discussed the relationship between the adsorption energy and the bond length of the single-atom catalyst system,and did a Bader charge analysis of the single-atom doped catalyst system for CO adsorption,and elaborated the relationship between the adsorption energy and the charge transfer.（2）In another study,catalysts with C-C coupling potential were further screened by the adsorption energy of single-atom catalysts for CO₂.The doping of transition metal Os can greatly improve the performance of the catalyst.We studied the adsorption mechanism of CO₂and the adsorption energy and adsorption sites of carbon monoxide molecules on the catalyst surface,focusing on the analysis of the electronic structure,and accurately predicted the adsorption sites by electrostatic potential.The results show that the adsorption of carbon monoxide and carbon dioxide molecules is greatly enhanced on the surface of the Os-doped catalyst.In addition,the doping of Os atoms can significantly promote C-C coupling.We explored an optimal reaction path for C-C coupling,identified the transition state,and proposed three key processes that C-C coupling undergoes.A detailed analysis of the complete reaction pathway for the reduction of carbon dioxide on the catalyst surface to ethylene and ethanol is made.