Preparation Of Copper-based Bimetallic Catalysts For Electrocatalytic Reduction Of CO₂

The massive consumption of fossil fuels has led to a rapid rise of the concentration of carbon dioxide in the atmosphere.People are eager to find a clean and efficient carbon dioxide conversion technology to reduce carbon dioxide emissions and develop value-added products.Among various carbon dioxide conversion technologies,the electrochemical carbon dioxide reduction reaction（CO₂RR）driven by renewable electricity can convert CO₂ into value-added chemicals and fuels,which is promising in future.Despite the obvious advantages of this strategy,there are still problems such as low CO₂ solubility and inevitable hydrogen evolution reactions in aqueous electrolyte system,and inefficient CO₂RR catalysts to be solved.Therefore,the exploration of catalysts with high activity,selectivity and stability is the key for the development of electrocatalytic CO₂ reduction.It is well known that metal copper（Cu）can reduce CO₂ to a variety of hydrocarbons and oxygen-containing compounds,including carbon monoxide,methane,ethylene,ethanol,etc.,which has attracted the most attention among various electrocatalysts.However,slow reaction kinetics,low product selectivity,and poor stability are the main drawbacks of single metal copper-based catalysts.Copper-based bimetallic catalysts exhibit great potential due to their unique electronic structure and synergistic interaction.Thus,this thesis aims to improve the performance of copper-based catalysts by introducing a second metal into copper.The main content includes the following two parts:1.CuSn bimetals used for electrocatalytic reduction of CO₂ to CO.In this work,nanowire structured CuSn bimetallic catalysts were prepared using wet chemical oxidation and electrochemical deposition methods.The relationship between the content of Sn atoms on the surface of the catalysts and their catalytic activity was studied.The results show that CuSn bimetallic catalysts can efficiently catalyze the reduction of CO₂ to CO,exhibiting superior CO₂ reduction activity.When the Sn deposition time is 60 s,the correspondingly prepared CuSn-60 sample exhibits the best catalytic performance.The Faradaic efficiency of CO is as high as 94.5%at a potential of-1.0 V（vs.RHE）,close to six times that of pure Cunanowires.In addition,the hydrogen evolution reaction（HER）was effectively inhibited so that the sample maintain stability for more than 20 hours.Electrochemical tests showed that Sn deposition on Cunanowires can provide more active sites for the reaction.The introduction of metal Sn may promote the desorption of the intermediate *CO and improves the selectivity of CO.2.CuAg bimetals used for electrocatalytic reduction of CO2 to C2H4.In this work,Cu（NO3）2 and Ag NO3 were used as precursors to prepare CuAg bimetallic composites with cluster structures comsisting of nanoparticles using Na BH4.The content of Ag is adjusted by the concentration of the precursor Ag NO3.The results show that pure metal Ag leads to a large amount of CO evolution within a wide potential range.After adding a small amount of Ag to Cu,the selectivity to C2H4 of CuAg bimetal is significantly improved compared to that of pure Cu.When the content of Ag is 2.98%,the sample has the best catalytic performance with the Faradaic efficiency of C2H4 close to 30.4% at-1.4 V（vs.RHE）.In addition,the hydrogen evolution reaction was effectively inhibited so that the sample maintain stability for more than 12 hours.Electrochemical tests show that the electrochemical active surface area of the electrode increases significantly after the composite of Cuand Ag.The introduction of Ag might provide a large number of *CO intermediates,which was conducive to promoting C-C bond coupling at Cusites and improving C₂H₄ selectivity.