1D Cu-based Nano-catalyst For Electrocatalytic CO₂ Reduction

Since industrialization,large-scale consumption of fossil fuels has led to unprecedented CO₂ emissions,which has led to a rapid increase in the greenhouse effect.To solve this problem,the fixation and conversion of CO₂ gas has become critical to achieving energy and environmental sustainability.The electrochemical reduction method can convert CO₂ into high value-added fuels and chemicals at room temperature,which provides an ideal solution for the carbon cycle.However,the strong chemical stability of CO₂ results in slow electrochemical kinetics and low product selectivity,which greatly limits its industrial application.Therefore,designing effective catalysts is particularly important for electrochemical reduction of carbon dioxide.It is worth noting that copper-based catalysts are considered to be very desirable electrocatalysts for electrochemical reduction of CO₂ due to their high activity and selectivity to hydrocarbon products.In addition,the large specific surface area and fast electron conduction rate of the one-dimensional nano-catalyst can greatly improve the catalytic performance of the catalyst.Based on the above reasons,this thesis will focus on the electrochemical CO₂ reduction performance of one-dimensional copper-based nanomaterials.The main research contents of this thesis are as follows:(1)One-dimensional Cu_1.8Se nanowires were successfully prepared by simple chemical oxidation and high temperature selenization methods.The morphological and structure characterizations revealed that Cu_1.8Se nanowires have a curved shape and a rough surface,which facilitated the full exposure of active sites.The results of electrocatalytic CO₂ reduction show that Cu_1.8Se nanowires can achieve the highest C2product selectivity at-1.1 V vs.RHE under the CO₂ pressure of 10 atm,and its Faraday efficiency is as high as 79%.Among the C2 products,the Faraday efficiency of C₂H₄and C₂H₅OH is 55%and 24%,respectively.Under the CO₂ pressure of 1 atm,the highest Faraday efficiency of C2 products obtained on Cu_1.8Se nanowires is only 59%,which indicates that the high CO₂ pressure is beneficial to the production of C2 products.In addition,Cu_1.8Se nanowires also exhibit excellent catalytic stability.During the continuous electrolysis for 25 hours,the current density of Cu_1.8Se nanowires and the Faraday efficiency of C2 products did not significantly decreased.(2)Cu₃N nanowires were synthesized by high temperature nitridation,and the nanowires were converted into Cu nanowires by in-situ electrochemical reduction.Spherical aberration corrected electron microscopy confirmed that Cu nanowires formed abundant grain boundaries during in situ electrochemical reduction.The appearance of a large number of grain boundaries makes Cu nanowires rich in catalytic sites,thereby improving their electrochemical performance.The results of the electrocatalytic CO₂ reduction test show that Cu nanowires exhibits the highest C1/C2product selectivity,and the Faraday efficiency of the C2 products is as high as 86%at-1.0 V vs.RHE.Similarly,during 28 hours of stability testing,the current density of the Cu nanowires and the corresponding Faraday efficiency of the C2 product did not decrease significantly,proving its excellent electrocatalytic CO₂ reduction stability.