Application Of Low Concentration CBM To Solid Oxide Fuel Cells With Nickel-based Anodes

Solid oxide fuel cell?SOFC?is an energy conversion device with high efficiency.Currently direct utilization of hydrocarbon as SOFC fuels is hotpot for SOFC applications.The state-of-art anode material of SOFC is based on nickel cermet anodes,which easily causes carbon deposition on the anode surface when using methane fuel.Therefore,enhancing the coking resistance ability of the anode material is a key to improve the long-term stability of SOFC.Global reserves of coal bed methane?CBM?are abundant.While low concentration coal bed methane?LC-CBM,CH₄ concentration below 30%?is difficult to be utilized due to the mixed air in large quantities.Most of them have been discharged into air or combustion invalidly during practical production.In view of this situation,this thesis develops a way to directly use LC-CBM as SOFC fuel to generate electricity by coating a catalyst layer on the anode surface.Based on the inherent propertities of LC-CBM,before they reach the anode surface,most of have been partially oxidized to syngas by the catalyst layer.The key is the preparation of catalysts with high catalytic activity and high sintering resistance at high temperature.Ce_0.8Sm_0.2O_1.9?SDC?powders were synthesized by sol-gel method,hydrothermal synthesis method and glycine combustion method,respectively.An anode supported single cell Ni-YSZ/YSZ/SDC/BSCF-SDC was prepared with 8%Y₂O₃ stabilized ZrO₂?YSZ?and SDC as electrolyte layers.We tested the electrochemical performance of cells using the three kinds of SDC electrolyte buffer layer,respectively.The results indicate that the the cell with SDC synthesized by hydrothermal method has the best performance.The NiO/BaO/CeO₂@SiO₂?@NBC?catalyst with a porous and core-shell structure was synthesized by coating SiO₂ onto the surface of catalyst NiO/BaO/CeO₂?NBC?,the mass fraction of nickel is approximately 11.5%in the restored@NBC.The structures and morphologies of the catalysts were characterized by XRD and TEM.The catalytic performance of the catalyst on simulated LC-CBM were studied using a fixed-bed device.Electrochemical performance and long-term discharge stability were studied by using electrochemically workstation for the@NBC-modified cell?@NBC//Ni-YSZ?.The NBC-modified cell?NBC//Ni-YSZ?and the blank cell without a catalyst layer?Ni-YSZ?were used for comparison.The results show that@NBC has high catalytic performance for the partial oxidation of 30%LC-CBM with the CH₄ conversion of 88%and CO selectivity of 91%at 800°C.@NBC was used as the anode catalyst layer of SOFC,and a mixture of 30%CH₄-70%air was used as fuel.The electrochemical performance and stability of@NBC//Ni-YSZ are greatly improved.The peak power density at 800°C increases by 50%compared with Ni-YSZ.@NBC//Ni-YSZ shows high stability under a constant current at 800°C for at least 168 h,while the voltage of NBC//Ni-YSZ rapidly decreases after 60 h,and Ni-YSZ has a drastic voltage drop after 10 h,indicating that the core-shell catalyst@NBC has good thermal stability.The@NBC-modified cell has good cooking-resistance.