The Performance Of Controlled Synthesis Of Specific Crysral Planes And Carbon Dioxide Reduction Of Copper Metal Catalysts

The electrocatalytic CO2 reduction reaction is a method of converting CO2 into high value-added chemicals.Among them,the hydrocarbons prepared from electrocatalytic CO2 has attracted widespread attention due to its high energy density and market price.However,under high current density,the low selectivity and instability of multi-carbon products limit its practical application prospects.Therefore,the development of catalysts with high selectivity to multi-carbon products has very important research value.This thesis carried out a series of research work on the design and synthesis of copper catalysts.By precisely controlling the structure of the catalyst to improve the selectivity to multi-carbon products,an efficient CO2 reduction electrocatalyst was prepared,and the intrinsic relationship between the dominant crystal face and the catalytic performance was discussed.The following research results have been achieved.1.Through in-situ potentiostatic electrodeposition of copper in different atmospheres,the specific adsorption of gases(such as CO2,CO,N2)and crystal planes is used to synthesize a series of copper metal catalysts that expose different crystal planes.And discussed its growth regular pattern and mechanism.Among them,the catalyst prepared under CO2 atmosphere(Cu-CO2)is rich in Cu(100)crystal planes,and the exposure of this crystal plane is conducive to the formation of C2H4 products.After the characterization of SEM,HR-TEM,XRD,OHadsorption and other technical means,it is found that the specific induction of Cu(100)crystal plane is achieved due to the selective adsorption of CO2 gas during the crystal growth process.This makes the ratio of the dominant crystal face area to the total area reach 56%,which is significantly higher than other copper catalysts.The catalyst Cu-CO2 is applied to the CO2 electrocatalytic reduction reaction.Under the condition of-1.4 V(vs.RHE),the current density of Cu-CO2 can be as high as 80 mA·cm-2,and the Faraday efficiency of C2H4 can reach 55%.The Faraday efficiency of C2+ reaches 69%.Through the comparison of the morphology,structure,crystal plane and catalytic performance of the synthesized catalyst under various gases,the catalytic mechanism of the highefficiency electrocatalyst Cu-CO2 was revealed,and the inducing effect of CO2 gas on the Cu(100)crystal plane was confirmed.2.By adjusting the pressure of CO2 gas atmosphere,the copper metal catalysts with different Cu(100)crystal face contents were synthesized by galvanostatic electrodeposition under different high pressure environments,And successfully proved the correctness and wider applicability of this strategy of using CO2 atmosphere to influence the surface characteristics of the catalyst.By studying the relationship between Cu(100)crystal plane content and catalytic performance,and optimizing the experimental conditions,the optimal CO2 atmosphere pressure was found to be 0.8 MPa.Compared with the catalyst synthesized under normal pressure(Cu-0 MPa),the copper catalyst prepared under the optimal conditions(Cu-0.8 MPa)has a Faraday efficiency(FE)growth for C2H4 from 31%to 50%in the electrocatalytic CO2 reduction reaction,the FE for C2+increased from 40%to 65%,and the corresponding OH-adsorbed charge of the Cu(100)crystal plane also increased from 5.9 μC ·cm-2 to 10.8 μC·cm-2.The study found that the content of Cu(100)surface crystal planes of all copper catalysts is positively correlated with the Faraday efficiency of C2H4,which proves the correlation between the selectivity of C2H4 and C2+and Cu(100)crystal planes.This paper not only provides a basis for the crystal growth regular pattern,but also provides a new idea for the rational design and preparation of highefficiency electrocatalytic carbon dioxide reduction catalysts.