Preparation Of Sm_0.5Sr_0.5FeO_3-δ Based Symmetric Electrode Material And Its Performance In Solid Oxide Fuel Electrolyzer

Solid oxide fuel cells（SOFCs）are considered to be a clean and efficient energy conversion device.At the same time,Solid Oxide Electrolysis Cells（SOECs）is the reverse reaction of SOFCs,can store electrical energy in the form of chemical energy through reverse power-on.Same ceramic oxide structure was used to the both sides electrodes of symmetrical Solid Oxide Fuel Cells（SSOFCs）,effectively avoiding Ni oxidation,carbon deposition and sulfur poisoning.Therefore,this paper studies a symmetric electrode material with good ORR and OER performance,and its SOFC and SOEC performance were systematically studied.In the third chapter of the thesis,a low-temperature stable ABO₃ perovskite structure oxide electrode material Sm_0.5Sr_0.5Fe O_3-δ（SSF）was designed.The commercial electrolyte YSZ as the support and the research results show that compared with SSF the polarization resistance of SSF-GDC composite electrode reduced from2.86 to 0.67Ωcm² and 4.32 to 0.91Ωcm²in air and H₂at 750℃respectively.The maximum power density of the SSF-GDC symmetric cell supported by the electrolyte YSZ at 750°C is 201.74 m W cm^-2,which is twice of the uncomposited GDC electrode.The long-term discharge for 20h has no attenuation at 700℃,indicating that it is a promising symmetric electrode material.Since the symmetric cell structure can effectively avoid the oxidation problem of the electrode under high water vapor concentration,the SSF symmetric electrode material was applied to study the performance of H₂O electrolysis.The conductivity under N₂ still exhibits semiconductor properties,and the maximum conductivity is 19.7S cm^-1.The cell performance test under humid hydrogen gas shows that it has good reversibility,and the 800°C maximum electrolysis current is 1025 m A cm² at 2V.In the case of direct N₂ with 20%water vapor,the maximum electrolysis current density at2V from 650 to 800℃increased from 267 to 1560 m A cm^-2.Finally,the long-term work data shows that there is no attenuation after running for 25h,indicating that this structure is an alternative to Ni-based electrolytic material.The fifth chapter mainly studies the performance of SSF for electrolysis of CO₂.Compared with electrolysis of H₂O,the electrolysis of CO₂ more difficult.Due to the presence of alkaline earth metal Sr in the material,Sr₂CO₃ is easily generated in an acidic CO₂ atmosphere,causing structural damage.Therefore,a small amount of high-valent element W was doped in B site to ensure the structure stability under CO₂.XRD shows that the material Sm_0.5Sr_0.5Fe_0.9W_0.1O_3-δ（SSFW）can maintain the structure stability under high temperature pure CO₂ atmosphere,and the maximum electrolysis current density is 1475 m A cm^-2 at 800℃.From the short-term results,there is still performance degradation under high voltage,but compared with no W doping,the performance is obviously stabilized.The EDS results of the cell after the test shows that there is no C element formation.The paper has 45 pictures,3 tables,and 103 references.