Dry Reforming Of Methane For Solid Oxide Fuel Cell Power Generation

This paper focuses on the application of dry reforming of methane（DRM）technology to solid oxide fuel cell（SOFC）and the effect of loading the catalyst reforming layer on the surface layer of the cell anode on the peak power density（PPD）and ohmic impedance（R_о）of the cell.Energy converter,converting chemical energy into electrical energy,with the advantages of efficient energy use and cleanliness.At present,increasing the power output and enhancing the long-term stability of the cell has been a hot topic of research in this field.DRM is applied to SOFC systems in the form of indirect internal reforming,using two greenhouse gases,CH₄ and CO₂,to catalyse syngas reforming（H₂ and CO）to provide a fuel source for SOFC.The main work of the thesis includes（1）the preparation of Ni-BaO-CeO₂（NBC）composite catalysts to facilitate efficient DRM reactions.（2）Integrating DRM with SOFC by loading the NBC catalyst reformer onto the surface layer of the cell anode to pre-catalyze the CH₄-CO₂ reaction to generate CO and H₂,which are less prone to carbon build-up,to improve cell power generation efficiency and enhance cell stability.（3）To solve the problem of increasing R_оdue to the loading of catalyst reforming layer on the anode of the cell,copper nanopowder was added to the NBC catalyst to increase the conductivity of the NBC catalyst reforming layer of the cell and thus reduce the R_оof the cell:1.The NBC composite catalyst was prepared by burning glycine to promote the DRM catalytic reaction.The DRM catalytic performance of NBC at 600～800℃ was tested by a fixed reaction bed.The results showed that the DRM effect of NBC catalyst was significant.97%conversion of CH₄and 80%conversion of CO₂was achieved by passing a 30 mL min^-1 gas mixture CH₄:CO₂（1:2）at 800℃.2.The DRM reaction was applied to SOFC by indirect internal reforming,and the electrochemical performance and long-term stability of the cell（NBC//Ni-YSZ）and bare cell（Ni-YSZ）were investigated by electrochemical ac impedance（EIS）and constant current discharge methods when the NBC catalyst was directly loaded on the anode surface layer.The results showed that the PPD of the NBC//Ni-YSZ cell was 0.629 W cm^-2and0.460 W cm^-2 at 800℃ and 750℃,respectively,when 60 mL min^-1 CH₄and CO₂（gas flow rate ratio 1:2）mixed fuel gas was introduced,which was 37.3%and 48%higher compared to the Ni-YSZ cell.In the long-term stability experiments,the Ni-YSZ cell decayed rapidly from 0.730 V to 0.293 V at a constant current density of 312 mA cm^-2 applied at 750℃ for28.6 h.In contrast,NBC//Ni-YSZ cells decayed slowly from 0.71 V to 0.50 V at a rate of0.009 V h^-1 after 62.7 h.This indicates that NBC catalytic reformer has a higher PPD than Ni-YSZ cells.The loading of the NBC catalytic reformer layer promotes the catalytic DRM reaction and reduces carbon build-up in the nickel-based SOFC anode,which has a significant effect on carbon build-up and cell structure stability in CH₄ fuel cell operation.3.The addition of nano-scale Cu powder to the NBC catalyst is expected to solve the problem of NBC//Ni-YSZ cell operation,where cell R_оincreases due to the low conductivity of the anode catalyst reformer layer.DC four-terminal method was used to test the conductivity of two catalytic reforming layer powders of 800～600℃.The experimental results are as follows:the conductivity of Cu-NBC powder at all temperatures is three times greater than that of NBC powder.And the EIS test results of the 800℃ cell showed a pattern of increasing R_оvalues in order:Ni-YSZ cell（0.221Ωcm²）<Cu-NBC//Ni-YSZ cell（0.231Ωcm²）<NBC//Ni-YSZ（0.244Ωcm²）.The experimental results show that the addition of Cu nanopowder to the catalytic reformer of the anode reduces the electron transport hindrance between the catalyst reformer and the anode,increases the conductivity of the catalyst reformer of the cell and thus reduces the R_оof the composite anode of the cell.