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Study Of CO2 Reduction Conversion And Its Electron Transfer Behavior

Posted on:2024-09-13Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y Z ZhongFull Text:PDF
GTID:1521306932958179Subject:Condensed matter physics
Abstract/Summary:PDF Full Text Request
Excessive emissions of CO2 have led to increasing CO2 concentrations in the atmosphere and have caused a series of environmental problems.Using renewable energy sources to reduce CO2 into high-value-added chemical products is an effective strategy to facilitate the carbon peaking and carbon neutrality goals.It is also a strategy to solve the regional and intermittent problems of renewable energy sources.However,the high thermodynamic stability of CO2 leads to its high activation energy barrier.Besides,the CO2 reduction process involves complex multiple electron transfer steps.Clarifying the electron transfer rules and influencing factors in the CO2 reduction conversion process to guide the design of an efficient CO2 reduction conversion pathway is a current research challenge.The essence of CO2 reduction conversion is the transfer and rearrangement of electrons after obtaining energy from the outside.In this process,the energy barrier of the electron transfer has a crucial influence on the reaction efficiency.Focusing on CO2 reduction,three efficient CO2 reduction methods were reported.Meanwhile,the electron transfer behavior and influencing factors in the process of CO2 electroreduction and plasma reaction were studied in depth.The strategy of combining single-atoms and molecular catalysts for efficient CO2 electroreduction to CO was proposed.A strategy to tune the pore size of porous Cu core-shell catalysts was designed for CO2 electroreduction to multi-carbon products.And the plasma CH4-assisted CO2 reduction strategy for rapid CO production was proposed.The specific content is as follows:1.Use the Co single atoms supported on the carbon black substrate as the sites to chemically anchor the phthalocyanine molecule.The obtained Co SAs-Pc catalyst was used for the efficient electroreduction of CO2 to CO.The Faradaic efficiency for CO was as high as 94.8%at-0.8 V vs RHE and only decreased by 2.5%after 10 h of operation.Studies had shown that the chemical anchoring of CoPc on the carbon black substrate enhanced the electron transport efficiency at the heterojunction interface,promoted the transfer of electrons to CO2,and finally generates CO.2.To further reduce CO2 to multi-carbon products,core-shell catalysts with Ag as the cores and porous Cu with different pore sizes as the shells were prepared.The influence of the finite effect generated by different pore sizes on the selectivity of multi-carbon products was investigated.When the catalysts with an average pore size of 4.9 nm in the porous Cu shells were operated at the current density of 300 mA cm-2,the Faradaic efficiency for the multi-carbon products was as high as 73.7%.The Finite-element analysis and in-situ IR test results indicated that the finite effect of the porous structure enhanced the local CO coverage and promoted the C-C coupling,increasing the odds of electron transfer to the*CO intermediates,thus facilitating the generation of multi-carbon products.3.To achieve a more rapid CO2 reduction rate,a plasma CH4-assisted CO2 reduction reaction was developed and its electron transfer behavior was investigated.In a magnetic rotating arc device,the highest CO yield of 803.2 μmol s-1 was achieved at a CO2/CH4 inlet ratio of 5/1 and a discharge current of 0.2 A.Using atomic emission spectroscopy,the active species during the reaction were analyzed.Combined with the product composition,the reaction pathway was analyzed.The temperature distribution of the discharge cross section was obtained by calculation of rotation temperature and Finite-element simulation,combined with the effect of temperature on the reaction rate coefficient,it was found that low cooling temperature was the key to suppress the H2 generation.
Keywords/Search Tags:CO2 reduction, molecular orbital, electron transfer, plasma reaction, Finite-element analysis
PDF Full Text Request
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