Preparation Of Cobalt-based Semiconductor Self-supporting Electrode And Their Application In Photoelectrocatalytic Reduction Of CO₂

Since the industrial revolution,the development of economy and human society has been accompanied by the consumption of large amounts of fossil fuels,which has released large amounts of the greenhouse gas CO₂ into the atmosphere,causing the climate and environmental crisis.Therefore,it is urgent to reduce the concentration of CO₂ in the atmosphere.As an artificial photosynthesis technology,photoelectrocatalytic reduction of CO₂ combines the advantages of photocatalytic and electrocatalytic reduction of CO₂,which can efficiently convert CO₂ into hydrocarbons with value-added chemicals and is one of the ideal strategies to mitigate the greenhouse effect.The metal organic frameworks（MOFs）and their derived materials have been extensively studied in the field of catalysis,including photoelectrocatalytic reduction of CO₂ because of their high porosity,metal active sites and morphology regulation.However,most MOFs and their derived materials are obtained in powder form and require adhesives to fix them on a carrier,which hinders mass transfer and reduces the number of exposed active sites,affecting their use in photoelectrocatalytic reduction of CO₂.As a powerful polymer processing technology,electrospinning technology can combine MOFs and polymers without altering the function of MOFs nanoparticles.This thesis uses electrospinning technology to prepare carbon nanofiber self-supported photoelectrodes loaded with MOFs-derived catalysts and investigates their performance for photoelectrocatalytic reduction of CO₂.（1）Preparation of self-supported electrodes of Co/Zn-CNF-X（X=4～8,indicating that the carbonation temperature is 400～800℃）and their photoelectrocatalytic reduction of CO₂ were studied.The ZIF-67/ZIF-8-loaded polyacrylonitrile（PAN）film was prepared by direct electrospinning,and the self-supported carbon nanofiber electrode（Co/Zn-CNF）loaded with cobalt-zinc oxide semiconductor was obtained by pre-oxidation and carbonization processes.The self-supported electrodes were tested by physical characterization such as SEM,TEM,XRD,XPS,Raman and FT-IR,and by photoelectrochemical tests such as UV-vis,LSV,EIS and transient photocurrent responses.The results show that the self-supported electrode Co/Zn-CNF-6 obtained by carbonization at 600°C exhibits the best reduction of CO₂performance,with a C₂₊product generation rate of 29μM h^-1cm^-2 at-0.6 V（vs.SCE）and a total electron transfer rate of 390+μM h^-1cm^-2.（2）Preparation of self-supported electrodes of Co/Cu-CNF-i and Co/Cu-CNF-m and their photoelectrocatalytic reduction of CO₂ were studied.Two self-supporting electrodes,Co/Cu-CNF-i（in situ growth catalyst）and Co/Cu-CNF-m（mixed catalyst and PAN）were prepared by electrospinning technology,respectively.The self-supporting electrodes were tested by physical characterization such as SEM,TEM,XRD,XPS,and FT-IR,and by photoelectrochemical tests such as UV-vis,LSV,EIS,and ECSA.The results show that the self-supported electrode Co/Cu-CNF-i has a better performance than Co/Cu-CNF-m,generating ethanol in a production generation rate of 27.5μM h^-1cm^-2 at-1.0 V（vs.SCE）and a C₂₊products generation rate of 37.5μM h^-1cm^-2,with a C₂₊selectivity of 75%.（3）Photoelectrocatalytic reduction of CO₂ to the production of high carbon alcohols and the amplification of syngas.Engineering research experiments were carried out in the horizontal scientific research project,such as the amplification and preparation of catalyst,the optimization of reaction conditions,and the extension of catalyst lifetime.The area of the electrode supporting catalyst was successfully enlarged from 1 cm×2.5 cm to 4 cm×10 cm,and the lifetime was extended from 2 h to more than 50 h.To carry out technical research on catalyst from laboratory to industrial large-scale application.