Study On The Preparation Of Copper-based Porous Nanocomposite And Its CO₂ Electro-reduction Performance

The intensification of human activities and the excessive use of fossil energy have led to increasing CO₂ concentrations.By 2019,CO₂ concentration in the atmosphere has reached around 411 ppm,resulting in many environmental problems,such as rising sea levels,greenhouse effect,tsunamis,as well as increasing land desertification.In order to alleviate or even solve those environmental problems caused by high level of CO₂,researchers have explored many methods including electrochemical methods,photochemical methods,and photoelectron-chemical methods to convert CO₂ into high value-added carbon-containing products.It is worth noting that electrochemical methods are the widely used methods due to its advantages of simple device and easy operation,environmentally friendly method and the feasible combination with other clean energy sources,such as wind energy,solar energy and tidal energy.Electrocatalytic CO₂ reduction?ECR?is currently the effective and ideal method to solve the problems caused by high CO₂ concentration.The inherent stability of CO₂ makes its activation difficult,and there is a strong competitive reaction?hydrogen evolution reaction?for ECR.Therefore,it brings great challenges for using electrochemical methods to convert CO₂ into valuable products.Metals,metal oxides,metal sulfides,and porous materials are explored to be able to improve the performance of ECR.The main product is the product that has a low electron transfer number,and Cu is a material capable of generating various multi-electron transfer products.In order to ECR to be applied in practice,it is important to obtain a material that produces a product with high energy density and is catalytically stable.The difficulty in achieving this goal lies in the only metal Cu that can produce a multi-electron transfer product.There are many types and low selectivity to a single product,which not only causes a great waste of resources,but also brings great difficulties to subsequent separation and purification.Therefore,the rational design of Cu and its derivatives has reached the goals of high selectivity,good catalytic stability and activity,which has great significance.In this paper,the preparation of copper-based porous nanocomposites and the study of its ECR performance are the main lines,and the following researches are carried out from the aspects of performance preset structure,material design,and material structure,combined with various advanced characterization techniques:1.A series of different transition metal supported porous organic polymer?COP?electrocatalysts were synthesized by aldol condensation reaction using metal phthalocyanine?M-TAPP?and terephthalaldehyde?BDA?,and their ECR performance was studied.Among electrocatalysts with different metal coordination,cobalt-phthalocyanine nitrogen?Co-PBCOP?shows good reduction performance.At-0.9 V,CO₂ can be selectively reduced to CO with a selectivity of 99.2%.In addition,based on Co-PBCOP materials,?-OH?or?-F?electron-withdrawing groups are introduced into the skeleton.It is found that Co-PBCOP-F?electron-withdrawing groups?greatly reduces electricity.Meanwhile,Co-PBCOP-OH?electron-donating group?retains the basis of the original catalytic performance,and improves the electrocatalytic performance of CO₂ at a lower potential?-0.6 to-0.7 V?,effectively improving the selectivity of CO.2.Using aniline to regulate the morphology of covalent organic framework materials?COF,COF-366-Cu?constructed by copper porphyrin and BDA,the microcrystalline COF was controlled to hollow spheres in situ,and more active sites were exposed,facilitating the mass transfer process of CO₂.The study found that the amount of aniline added will affect the morphology of COF,and the morphology has a certain degree of influence on the selectivity of the product of ECR.When the amount of aniline added is 5?l,the more uniform hollow spheres of COF-336-Cu-1 had excellent selectivity for CH4(-1.1 V,FE_CH4=64.8%).3.The use of soluble copper and carboxyl oxygen-coordinated metal organic polyhedron?MOP?and porous graphite carbon to further carbonize the copper and porous carbon substrate composite material to study the CO₂ electroreduction performance.It was found that loading a suitable amount of copper?Cu@C-glucose?1:1??on porous carbon improves the catalytic selectivity to CH₄(-1.1,FE_CH4=73.5%)and has good stability.