Anodic Mechanism And Reaction Characteristics Research On Liquid Antimony Anode Direct Carbon Fuel Cells

Liquid antimony (Sb) anode direct carbon fuel cell (DCFC) is one of the promisingpower generation technologies. The studies in the anodic mechanism and reactioncharacteristics are significantly important for the DCFC development. This dissertationpresented systematic researches on the liquid-Sb-anode DCFC anodic reactionmechanisms and the reaction characteristics in various operation conditions. Further, aprototype of the liquid-Sb-anode DCFC was built.The liquid-Sb-anode intrinsic reaction characteristics and interfacial reactioncharacteristics were studied by using smooth single crystal YSZ electrolyte with surfaceroughness Ra=0.69nm. At800oC, the intrinsic liquid-Sb-anode exchange currentdensity is141.4mA/cm2, while anodic resistance is only0.143cm2. The contactangles of liquid Sb and Sb2O3on single crystal YSZ are respectively45oand0o, whichmeans that the Sb2O3was able to improve the contact area between the liquid-Sb-anodeand the electrolyte. When the surface roughness Ra was kept at540nm, the contact areabetween the liquid-Sb-anode and the electrolyte increases by38%, and it means that theexchange current density of the liquid-Sb-anode can be improved by tuning surfacemorphology.In the liquid-Sb-anode, the main reaction route of carbon conversion is3C+2Sb2O3=4Sb+3CO2with90%CO2in the off-gas. Due to the low diffusion rate ofCO in liquid Sb，it is hard for the carbon conversiton intermediate product CO to reduceSb2O3in the liquid-Sb-anode immediately. Carbon and CO electrochemical reactionswith O2-happened at the anode-electrolyte interface; however, they were not able toimprove the cell performance, due to the lack of effective catalyst.Taixi de-ash coal recovered the liquid antimony anode fuel cell performance up tothe initial performance at battery mode. Liquid Sb layer prevented impurities in thede-ash coal from accumulating at the anode-electrolyte interface. The de-ash coal istransported in liquid-Sb-anode through diffusion and natural convection. However, dueto the viscidity effects, the natural convection is not obvious.A fluidized bed liquid-Sb-anode direct carbon fuel cell prototype was proposed andbuilt by using an electrolyte supported tubular solid oxide fuel cell, and achieving a continuous carbon fuel feed and stable operation, which verified the feasibily forapplying the fluidized bed electrode used in liquid-Sb-anode DCFC. For the proposedfluidized bed liquid-Sb anode direct carbon fuel cell prototype, the fuel cell efficiencyreached up to41%, with the carbon fuel utilization ratio up to90%.