Research On The Mechanism Of Catalytic Conversion Of CO₂ By MES And Synthesis Of Small Molecule Organic Compounds

The massive emission of carbon dioxide has led to a serious greenhouse effect,posing a serious threat to human survival and social development.As a major international issue affecting the future world economy and environment,carbon dioxide emission reduction is also an important component of my country’s sustainable development strategy.Bioelectrosynthesis technology can use clean and renewable energy to achieve high-efficiency conversion of CO₂,while also reducing greenhouse gas emissions.This paper takes carbon dioxide as the research object,and on the basis of summarizing the research status at home and abroad,the microbial electrosynthesis is used to study the carbon dioxide reduction process.The main findings are as follows:（1）Using titanium nanotubes as a carrier,high-vacuum magnetron sputtering graphene on the surface to prepare nano-titanium carburizing electrodes and the Gr@Nano-Ti plate is used as the MES cathode,the final accumulation of acetic acid increases from 139 mg·L^-1to 139 mg·L^-1during the process of potential from-0.40V to-0.70V 237 mg·L^-1;when the cathode potential drops to-0.80V,its final accumulation drops to 206 mg·L^-1.The accumulation of butyric acid also reached the maximum at-0.7V,and the maximum value was 64 mg·L^-1.According to electrochemical analysis,the average current value of the titanium-based carburizing electrode system was at-0.80 V.,The maximum can reach 6.68 m A,and all have a reduction peak near-0.59 V.When the potential intensity is-0.70 V,the maximum total coulombic efficiency of the system is85.10%,and the minimum coulombic efficiency is 62.20%at-0.40 V.（2）When using carbon felt as the carrier and using graphene modified carbon felt as the MES cathode,when the cathode potential is-0.80 V,the maximum accumulation of acetic acid is 250.04 mg·L^-1,and the maximum accumulation of butyric acid is 84.87mg·L^-1,the total coulombic efficiency reaches 85.31%.（3）The response surface method（RSM）is used to optimize the various influencing factors of MES electro-reduction of carbon dioxide,and the coulombic efficiency quadratic regression model is established through the central composite design（CCD）to determine the significance of the interaction between the factors:The results of the Gr@Nano-Ti plate system show that the cathode potential has an extremely significant impact on the coulombic efficiency of the system,the reaction time has a significant impact on the coulombic efficiency of the system,and the reaction temperature has no significant impact on the coulombic efficiency.The most sui Tabreaction conditions are:temperature 30.2℃,cathode When the electric potential is-0.73 V and the reaction time is 6.1 d,the coulombic efficiency reaches the maximum value,which can reach 86.2%.The error between the predicted value and the experimental value is less than 2%;the graphene modified carbon felt electrode test group tested the MES according to the response surface model The reaction conditions are optimized,and the most sui Tabreaction conditions are:temperature 29.8℃,cathode potential-0.78 V,reaction time 5.3 d,the coulombic efficiency reaches the maximum value,the maximum can reach 92.3%,the error between the predicted value and the experimental value Less than3.5%.（4）High-throughput sequencing technology was used to analyze the microbial community structure on the surface before and 10 days after the MES reaction:the dominant strains of the original sludge in the Gr@Nano-Ti electrode MES system were Clostriclium and Butyribacterium,their abundances were 26.48%and 12.37%,and their abundances were 38.29%and 6.84%after the reaction.In the MES system of graphene-modified carbon felt electrode,in the inoculated sludge,Accounted for 23.50%of the total flora.In the system operation stage,the proportion reached 51.90%of the total flora after 10 days of reaction.Annotated Clostridium KEGG gene function,and found that it contains genes encoding acetate kinase（ack）and butyrate kinase（buk）and other related synthetic organic acids,and these genes are generally considered to be acetate and butyrate formation Key genes.（5）Using the quantum chemistry software VASP based on the density functional theory to speculate on the conversion process of carbon dioxide in the bioelectrochemical reduction process,combined with the functional annotations of the KEGG gene of the bacteria,the metabolic pathways that constitute the synthesis pathway of acetic acid and butyric acid are studied.The schematic diagram shows the possible reduction path of carbon dioxide.