Study Of Preparation And Performance Of LST/YSZ Composite Fiber-Based Fuel Electrode For Reversible Solid Oxide Cells

Reversible solid oxide cells（RSOCs）could realize the sustainable cycle of clean energy and electricity under SOFC/SOEC dual mode,and play the role of"peak-shifting and valley-filling",which have broad application in the construction of energy internet.Conventional Ni-YSZ fuel electrode materials are susceptible to sulfur poisoning when using fuel gas containing sulfur impurities and carbon buildup when using hydrocarbon fuel.Strontium titanate（Sr Ti O₃）perovskite materials are the most widely studied fuel electrode materials for RSOCs because of their highly adjustable structure and performance,good structural and thermochemical stability and strong resistance to carbon deposition and sulfur poisoning.Conventional particle-based fuel electrodes are obtained by adding pore-forming materials with low porosity and connectivity,therefore the catalytic activity of fuel electrodes should be further improved through improving the electrode preparation method and optimizing the fuel electrode morphology.In this study,LST/YSZ composite fibers were directly prepared by electrospinning method,the effect of different impregnant modifications on the electrochemical performance of fuel electrodes under SOFC/SOEC dual mode were investigated,and the mechanism of nanoparticle exsolution on the electrochemical performance of fuel electrodes was explored by modulating the impregnation process.The main findings are as follows:（1）By adjusting m（PVP）/m(Mⁿ⁺)and the LST/YSZ mass ratio,the electrospinning solutions with stable spinning,high filament production efficiency and products meeting the requirements of fiber-based fuel electrode morphology were prepared.The results showed that the electrospinning solution was prepared by m（PVP）/m(Mⁿ⁺)=0.5 and LST/YSZ=6:4,and the LST/YSZ composite fiber with obvious fiber morphology,uniform embedding of YSZ particles and uniform diameter（150～200 nm）was obtained through spinning and calcination,which can be used for the subsequent preparation of fuel electrodes.（2）The LST/YSZ composite fiber was used to prepare the fuel electrode skeleton.Ce_0.9M_0.1O_2-δ（M=Fe,Co,Ni）precursor solution was prepared to impregnate and modify the fuel electrode.The RSOCs single cell supported by YSZ electrolyte were prepared to test its electrochemical performance under SOFC/SOEC dual mode.The results showed that the impregnate uniformly wrapped on the fiber surface to strengthen the interfacial bonding between the fuel electrode and the YSZ transitional layer;the fuel electrode using Ce_0.9Ni_0.1O_2-δas the impregnate was found to have more Ni nanoparticles exsolution after the testing.The prepared single cell has the most excellent electrochemical performance,reaching at 342 m W/cm² at 850℃and 3 vol.%H₂O/H₂ and 0.313 A/cm² under 46.8 vol.%H₂O/H₂,1.3 V electrolysis.（3）To investigate the mechanism of Ni nanoparticles exsolution to enhance the electrochemical performance of the fuel electrode,the fiber-based fuel electrode with strong catalytic activity in SOFC/SOEC dual mode was prepared.The surface modification of the fuel electrode was carried out by adjusting the amount of CNO impregnation and Ni content.It is shown that the appropriate amount of Ce_0.8Ni_0.2O_2-δ(CN_0.2O)impregnation could help the exsolution of uniformly dispersed Ni nanoparticles on the fuel electrode surface,which significantly enhances the interfacial charge transfer and the adsorption and dissociation of hydrogen and water vapor,and further improves the catalytic activity of the fuel electrode.However,too much impregnation will block the pores and increase the concentration polarization.The 5CN_0.2O@LY+YSZ single cell with the mass ratio of LST/YSZ/CN_0.2O=6:4:4.3 has both high performance under SOFC and SOEC dual mode,with a maximum power density of 375 m W/cm²at 850℃and 3 vol.%H₂O/H₂ and a current density of 0.331 A/cm² under 46.8 vol.%H₂O/H₂,1.3 V electrolysis.