Research On Symmetric Electrode Of MnCr₂O₄ Spinel For Solid Oxide Fuel Cell

Solid oxide fuel cell（SOFC）is a energy conversion device with high efficiency and no pollution that converts chemical energy stored in fuels into electrical energy directly.As a result,it has high energy efficiency.Therefore,the commercialization and industrialization of SOFC is of vital significance for the realization of energy conservation and emission reduction,as well as the alleviation of environmental pollution and resource shortage.SOFC also has the advantages of wide applicability of different fuel species,high fuel efficiency,co-generation of electricity and heat,modularization,etc.It has a broad application and development prospect in distributed power stations,household electricity,shipbuilding industry,aerospace and other fields.Concerning that traditional SOFC works at high temperature（800¹000℃）which may cause issues such as solid phase reaction of different parts and severe performance degradation,SOFC gradually develops to the intermediate-low temperature range（600⁸00℃）.The decrease of working temperature has a great influence on electrode.As a result,it is necessary to develop new electrode materials with high electrochemical performance in the intermediate-low temperature range.In recent years,researchers have attempted to use the same material as both anode and cathode for SOFC,commonly called symmetric SOFC.Symmetric SOFC can simplify sintering process,improve thermal compatibility of the cell and reduce the production and manufacturing costs.In this paper,a series of studies are carried out on the basic properties of MnCr₂O₄spinel.The properties of MnCr₂O₄ as a symmetrical SOFC electrode material are effectively improved by optimizing the microstructure of the electrode.The main research results are as follows:（1）MnCr₂O₄ powder prepared by glycine nitrate synthesis method has fine particle size,uniform distribution and good chemical compatibility with electrolytes.The powder prepared contains a small amount of Cr₂O₃ due to partial substitution of Cr³⁺in the octahedral sites by Mn³⁺.While under the reduction atmosphere,Mn³⁺is reduced to Mn²⁺,and Cr³⁺returns back to octahedral sites.As a result,Cr₂O₃ phase disappears.（2）Compared with the electrode prepared by the traditional mechanical mixing method,the MCO-GDC electrode prepared by the co-infiltration method has a higher three-phase interface length,high activity and better electrochemical performance.Through our research on electrochemical performance under different atmospheres,the co-infiltrated composite electrode possesses good oxygen evolution reaction（Oxygen Evolution Reaction,ORR）activity and hydrogen oxidation reaction（Hydrogen Oxidation Reaction,HOR）activity.And the symmetric cell also shows good performance.By using wet H₂ as fuel gas,the maximum power density reached 393 mW·cm^-2 at 800°C.The cell can further be applied to SOEC mode to electrolyze pure CO₂,and a current density of 0.731 mA·cm^-2 was obtained at 800°C and 1.5 V.（3）The NiO-YSZ anode support cell was prepared by using the co-infiltrated MCO-GDC electrode as cathode.Due to the decrease of the electrolyte thickness,the electrochemical performance of the cell was greatly improved.The peak power density reached 665 mW·cm² at 800℃.