Application And Research Of Electrospun Oxides In Proton Conductor Solid Oxide Fuel Cell

Energy is the foundation of economic development and is related to the national economy and people’s livelihood.In order to realize the sustainable development of society,the development of clean and efficient energy conversion device has become the primary issue facing the society.Solid oxide fuel cells（SOFCs）are emerging with advantages of high efficiency,good stability,good flexibility and low pollutant emission.The application of proton conductor oxide electrolyte further promotes the development of SOFCs at low temperature,solves the problem of mechanical and chemical compatibility caused by high working temperature to a certain extent,and shortens the start-up time of the cell.However,in proton conducting solid oxide fuel cells（H-SOFC）,compared with the anode,the oxygen reduction reaction of the cathode is usually several orders of magnitude slower,which severely restricts the output power of the cell.It is very important to develop suitable cathode materials for H-SOFC to exhibit high electrochemical performance at medium and low temperatures,which will promote the commercialization of H-SOFC.In addition,the improvement of preparation methods and morphology is another major challenge to improve the performance of H-SOFC,and the development of electrospinning technology in recent years has brought a new direction and great potential for the construction of high-performance H-SOFC cathode materials.Based on this background,we prepared three kinds of H-SOFC cathode materials by electrospinning method,and investigated their feasibility as H-SOFC cathodes.The main contents of the study are as follows:（1）La_0.5Ca_0.5MnO_3-δ（LCaM）cathode material doped with calcium at the A site of perovskite-type oxide LaMnO₃was prepared by electrospinning.By characterizing the composition and microstructure of the material,it is proved that using LCaM nanofibers as cathode can effectively improve the performance of H-SOFC.After calcination at high temperature,the size of the nanofibers shrinks to 280 nm and forms a network structure interleaved with each other.The unique nanofiber structure provides higher surface area and porosity of the electrode,while also providing a"shortcut"for the transport of ions and oxygen during electrochemical reactions.The R_pat 700℃is only 60%of that of LCaM powder cathode.Whether microwave sintering or conventional sintering is used,the output power at 700℃is significantly higher than that of the cell with sol-gel LCaM cathode.The analysis of XPS also shows that the decrease of the average valence state of Mn ions leads to more oxygen vacancies,which is very important to promote the oxygen reduction reaction of the cell.It shows that the electrospinning technology can effectively improve the microstructure of the cathode,thus improving the performance of H-SOFC.（2）La_0.5Sr_0.5Mn_0.875Zn_0.125O_3-δ（LSMZn）nano-powders were prepared by electrospinning as cathode materials for H-SOFC.The results show that for LSMZn,the phase formation temperature can be effectively reduced by electrospinning,and the particle size and size distribution of the material can be improved,which helps to increase the oxygen vacancy content of the material and thus improve the oxygen reduction reaction ability.This conclusion is also confirmed by the results of first principles calculations.The cell prepared by electrospinning LSMZn cathode has a peak power density of 1122 m W cm^-2at 700℃,which is significantly higher than the cell with sol-gel LSMZn cathode,and has passed the stability test for 200 h.（3）The pure LiFeO₂was tried to be used as the cathode material of H-SOFC.Compared with H-SOFC,this kind of Li-embedded compounds are more often as electrode materials for lithium ion batteries.But in fact,there are many things that can be learned from each other in the selection of electrode materials for lithium-ion batteries and fuel cells.In this study,pure LiFeO₂cathode material was synthesized by electrospinning for the first time,which improved the adhesion to Ba Ce_0.7Zr_0.1Y_0.2O_3-δ（BCZY）electrolyte.This is mainly due to the reduction of particle size and the improvement of size distribution.While improving the performance of the cell,it also ensures the long-term stability of LiFeO₂material under acidic atmosphere（CO₂）.