Study On The Electroreduction Of Carbon Dioxide To Hydrocarbons By Regulation Of Copper-based Catalysts

Global unlimited carbon dioxide(CO₂)emissions have caused serious environmental pollution and climate change.The electrochemical reduction of CO₂ is favored by scholars at home and abroad because of its higher reduction efficiency and relatively simple experimental environment so as to realize the real carbon cycle.Copper based materials are the most likely catalysts for the efficient conversion of CO₂ to hydrocarbons,but they also face the problems of poor product selectivity and stability.In this paper,a series of copper based materials were designed and synthesized to explore the factors influencing the catalytic performance and selectivity of CO₂ electrochemical reduction,as well as the research of catalytic mechanism,so as to obtain copper based catalysts with high efficiency of catalyzing CO₂ toward hydrocarbons.The main contents of this paper are as follows:1.Metal organic framework(MOFs)has the characteristics of porous and adjustable structure,based on the solubility difference of reactants in mixture solvents,Cu adenine MOFs(Cu-ade MOFs)with different morphologies were synthesized.The cathodized Cu-ade MOFs nanosheets demonstrate excellent catalytic performance for the CO₂ conversion into valuable hydrocarbon with a total hydrocarbon Faradaic efficiency(FE)of over 73%.Mainly,ethylene(C₂H₄)with a maximum FE of 45%is produced at-1.4 V vs.RHE with a current density of8.5 m A cm^-2,while methane(CH₄)demonstrates FE of 50%and current density of?15 m A cm^-2 at-1.6 V vs.RHE.These investigations reveal that the reconstruction of cathodized Cu^II/ade-MOF and the formed Cu nanoparticles functionalized by the nitrogen-containing ligands contribute to the excellent CO₂ conversion performance.2.The MOFs materials are unstable in the process of electrocatalysis,so the nanowires of Cu-ASP MOFs prepared by liquid-liquid interface method are used as the precursor.By adjusting the annealing conditions,the crystal state and surface structure of the materials are regulated,and combined with the strategy of in-situ reduction to form oxide derived copper materials,the high selective reduction of CO₂ to C2 products(C₂H₄ and C₃CH₂OH)is realized,the highest C2 product FE is about 70%at-1.3 V vs.RHE.The excellent activity and selectivity of cupric oxide nanowires is mainly relative to the unique porous structure with abundant interface.Moreover,the in-situ Raman spectra indicate that the metallic copper would be the real active sites for the CO₂ electrolysis.3.Various copper oxide with different oxidation states(Cu⁰?Cu⁺)was prepared via liquid phase reduction method,the effect of Cu catalysts with different oxidation states on the activity and selectivity of electrocatalytic reduction of CO₂ was investigated.For Cu₂O with high oxidation degree,with the decrease of voltage,the FE of C₂H₄ decreases and the FE of CH₄ increases.With the decrease of oxidation degree on Cu catalysts,CH₄ is largely suppressed and C₂H₄ definitely dominates at a wide potential window.Thus,the optimal oxidation state of copper can obtain high efficiency of C2 hydrocarbons(C₂H₄ and CH₃CH₂OH).The highest FE of C2 hydrocarbons is 74%and the FE of C₂H₄ is about 53%.4.The CuI catalyst was synthesized using Cu₂O nanoparticles precursor by ion exchange method.The effect of anions on the activity and selectivity of electrocatalytic CO₂ reduction was investigated.Compared with Cu₂O,CuI has high current density and tend to produce C2(C₂H₄ and CH₃CH₂OH)products under the whole applied potential.The FE of C2 products is about 53%at-1.3 V vs.RHE.Because I ion in CuI catalyst helps to form and stabilize the intermediate of C2 species,thus effectively converting CO₂ into hydrocarbons.