Study On Doping And Microstructure Modification Of Cathode Of Proton Conductor-based Solid Oxide Fuel Cell

With the increasingly prominent problems of energy shortage and environmental pollution,the development of new and efficient clean energy become one of the world's focal points today.Solid oxide fuel cell(SOFCs)has been widely concerned in scientific research and industrial application.Because solid oxide fuel cells can convert chemical energy directly into electric energy,and due to its high conversion efficiency,pollution-free characteristics,SOFCs may become a new generation of energy materials that can be widely used.The traditional oxygen ion-based solid oxide fuel cell(O-SOFCs)has been used in industry,but because of its high operating temperature,it needs a high demand for the working environment,and at the same time,it speeds up the wear and tear of the equipment-Working under high temperature for a long time can also bring some safety risks.Compared with O-SOFCs,proton based solid oxide fuel cells(H-SOFCs)can operate at lower operating temperatures due to lower activation energy.However,with the decrease of operating temperature,the polarization resistance of the battery will rise sharply,which has a great impact on the output power of the single cells.The influence of cathode material on polarization resistance is very important,so it is of great significance to develop high-performance and stable cathode material for H-SOFCs.This paper focuses on the development and improvement of H-SOFC's new cathode materials.By means of doping modification and cathode micromorphology modification,the electrochemical properties and stability of SOFCs can be improved,so that it can obtain good output power and long-term stability under medium and low temperature conditions.The first chapter of this paper mainly describes the research background of solid oxide fuel,focuses on the working principle of SOFCs,electrode materials and electrolyte materials,and introduces the experimental technology used in this paper.In chapter 2,the cathode materials series BaFe0.8-xSn0.2BixO3-?(X=0,0.1,0.2,0.3,0.4 and 0.5)co-conductance of electrons,ions and protons obtained through doping modification of metal cations were studied.Electrochemical tests and theoretical calculations were carried out on these cathode materials.The results showed that BaFe0.8-xSn0.2BixO3-? material had excellent electrochemical properties.In a single cell with the structure of NiO-BaZr0.1Ce0.7Y0.2O3-?| BaZr0.1Ce0.7Y0.2O3-?|BaFe0.5Sn0.2Bi0.3O3-?(BFSBi0.3),the power density reached 1277 mwcm-2 at 700?.Compared with other cobalt-free proton conductor base cathode materials,BFSBi0.3 has excellent electrochemical performance and long-term stability.This study opens up a new way for the design of proton conductive soft cathode.In chapter 3,the proton conductivity and REDOX activity of barium ferrite cathode materials were improved by using zinc ions reported in literature to obtain the cathode materials of BaFe0.8Zn0.1Bi0.1O3-?(BFZB).Further improvements were made in the process.BaZr0.1Ce0.7Y0.2O3-? was used as the cathode base to enhance the bonding ability with electrolyte,and then BFZB nanoparticles was impregnated on the base.To further improved the performance of the single cells.In chapter 4,the doping of high-value ion Ta5+improves the stability of the cathode material Ba0.5Sr0.5Co0.8Fe0.2O3-? of the classical solid oxide fuel cell,and studies the electrochemical properties of the cathode material Ba0.5Sr0.5Co0.8Fe0.2-xTaxO3-?(X=0,0.1,0.2)series.Results showed that the Ba0.5Sr0.5Co0.8Fe0.1Ta0.1O3-? cathode material not only has good electrochemical performance,but also has a good stability.These studies are of great significance for the application of H-SOFCs in industry.The fifth chapter makes a summary of the research in this paper,and puts forward a prospect for the future research and application of SOFCs.