Research Of Novel Oxygen Electrode Material And Structure Of Solid Oxide Electrolysis Cell For H₂O-CO₂ Co-electrolysis

Solid oxide electrolysis cells?SOEC?as advanced electrochemical energy storage and conversion devices have high conversion/energy efficiencies.Co-electrolysis H₂O and CO₂ using SOEC to produce syngas?H₂ and CO?could effectively reduce CO₂ emission and store eco-friendly electricity energy into stable chemical energy,like hydrogen and syngas.It provides a feasible way to solve the environment problems caused by greenhouse gas emission,and can make better use of renewable energy.Solid oxide electrolysis cell commonly operates at high temperature,like 600¹000°C,which can largely reduce the consumption of electricity energy and obtain higher conversion efficiency during electrolysis process.SOEC could use electricity generated by new energy technology?solar,wind,geothermal energy,etc.?and waste heat in industrial process,enabling efficient and eco-friendly energy conversion.SOEC as the inverse process of solid oxide fuel cell?SOFC?has many similarities among them.However,due to the different working conditions,SOEC has higher requirements on material selection and structural design.In addition,the co-electrolysis process becomes highly complicated,because of the existence of reverse water gas shift?RWGS?.Therefore,it is necessary to research and develop novel materials and structures for SOEC to meet its working conditions,and explore the influence of operation conditions on the process of co-electrolysis of H₂O and CO₂.The main research conclutions are as follows:?1?A mixed ionic and electronic conductive material La_0.8Sr_0.2Co_0.8Ni_0.2O_3-??LSCN?with perovskite structure was prepared by polymer-assisted combustion synthesis method.The cell with LSCN-GDC composite oxygen electrode was fabricated by screen-printing and shows great electrochemical performance at SOFC mode.In the research of co-electrolysis of H₂O and CO₂,the cell shows good catalytic performance and long-term stability as well.By investigating the performance of the cell under different feed gas compositions,it was confirmed that bath H₂O and CO₂ was reduction by electrolyte during co-electrolysis process.?2?In order to improve the oxygen evolution reaction?OER?activity,the LSCN impregnated GDC-LSM composite oxygen electrode cell was prepared by impregnation method.In SOFC mode,the peak power density reached 1057 mW cm^-2 at 800°C.When working as SOEC,the current density of the cell reached 1.54 A cm^-2 at 800°C with 1.5 V.After studying the change of cell performance under different operation conditions?like,gas composition,operating voltage or current,operation time,etc.?,the reaction mechanisms during co-electrolysis was analyzed.In the process of co-electrolysis,although part of CO₂ was transform to CO by electrolyte,the CO₂ conversion was mainly depended on RWGS reaction;H₂O was mainly reduced by electrolysis.The relationship between the production of co-electrolysis and operating conditions was analyzed by a co-electrolysis chemical equilibrium mode.?3?A LSCN impregnated oxygen electrode cell with gradient porous structure was designed and fabricated.The test results show that the electrochemical performance of the cell increased in both SOFC and SOEC modes.In the SOFC mode,the peak power density of the cell reaches 1.383 W cm^-2 at 800°C.In the co-electrolysis test,the current density of the cell reaches 1.548 A cm^-2 at 800°C and 1.3 V electrolysis voltage.The degradation rate is about 4.019×10^-4 V h^-1 during the long-term performance test for co-electrolysis of H₂O and CO₂ at 800°C,400 mA cm^-2 over 90 h,indicating that the cell has high electrochemical performance and stability during co-electrolysis process.