Application Of Polyimide Covalent Organic Frameworks In Electrochemical Carbon Dioxide Reduction Reaction

Over the past half century,rapid population growth has led to a substantial increase in energy demand and CO₂ emissions,causing a series of environmental problems.Electrochemical CO₂ reduction reaction from renewable energy sources provides a practical way to reduce CO₂ concentration in the atmosphere,fuel production and promote natural carbon cycle.At present,the electrode materials with catalytic activity,such as metal-based,non-noble metal-based and molecular catalysts,have made gradual progress,however,there are still some challenges,such as high price,complex synthesis method,low catalytic activity and low stability.Therefore,it is urgent to design and synthesize a cheap,simple,efficient and stable electrochemical CO₂ reduction reaction catalyst.In this paper,the polyimide-based covalent organic frameworks（PI-COF）with good crystal structure were constructed by using cheap and easy-to-obtain organic materials and simple synthesis method,the design and synthesis of self-supported non-metallic catalysts and highly dispersed copper catalysts with electrochemical CO₂ reduction reaction performance were realized.The specific research contents and results are as follows:1.The synthesis methods of different PI-COF materials were investigated,and the self-supporting PI-COF-CP catalysts with electrochemical CO₂ reduction reaction activity were successfully prepared by in-situ growth technique.Through the characterization of materials science,we found that the two-dimensional PI-COF nanosheets were stacked along the carbon paper fibers to form microspheres,which can efficiently reduce CO₂ to CO under electrochemical conditions,Under the conditions of-0.6 V vs RHE potential,Faraday efficiency can reach 93.1%,which is much higher than that of polymer materials obtained from other synthesis methods.In addition,the self-supporting electrocatalyst has strong anti-decay ability and can maintain Faraday efficiency above 80%under 24 h continuous electrolysis.2.Further copper nanoparticles,cuprous oxide nanoparticles and copper（I）sulfide nanoparticles were doped into the PI-COF synthesis.It was found that PI-COF grew along the cuprous oxide spheres,the cuprous oxide are anchored to the surface of the lamellar structure.At the same time,the effect of doping different copper-based materials on the catalytic performance of electrochemical CO₂ reduction reaction was investigated.The results showed that the doping of copper nanoparticles and copper（I）sulfide nanoparticles had no effect on the catalytic performance of PI-COF.The doping of cuprous oxide alters the products of CO₂ reduction reaction,resulting in higher calorific value hydrogenations.