Preparation Of R-P Fe-based Perovskite Cat-hode Material For Solid Oxide Electrolyzer And Study On CO₂ Electrolysis Performance

As an energy conversion device,Solid Oxide Electrolysis Cells（SOECs）can use electrical energy generated by clean energy such as solar energy,wind energy,and nuclear energy as power to convert electrical energy into chemical energy.Carbon dioxide or water vapor is often electrolyzed into carbon monoxide or hydrogen at high temperature,which can not only solve the energy crisis,but also alleviate environmental problems,which has attracted a lot of attention.With the research on the electrolysis of CO₂ in the electrolytic cell,it was found that the largest rate-limiting link in the electrolysis reaction is the oxidation-reduction process of CO₂.Therefore,the development and design of cathode materials has become the main research direction of the electrolytic cell.In the research process of solid oxide electrolytic cell cathode materials,it is found that although metal/ceramic oxide composite（Ni-YSZ）as a traditional cathode material shows good electrochemical catalytic ability when electrolyzing gas at high temperature.However,Ni-YSZ is prone to Ni oxidation and agglomeration during the operation of electrolytic CO₂,which seriously affects the electrolysis rate of the electrolytic cell;in addition,the catalytic activity of metal nickel on CO₂ cracking is relatively high,and carbon deposition is very likely to occur,leading to the battery Performance degradation restricts the application of Ni-YSZ.Perovskite-type oxide electrode is a very potential alternative electrode,which has the advantages of ion-electron mixed conductivity（MIEC）,good oxidation-reduction stability,and low cost.This article mainly focuses on RP（Ruddlesden-Popper）type layered perovskite oxide as a SOEC cathode material.In this paper,La_0.5Sr_0.5FeO_3-δ and RPLaSrFeO_4-δ cathode materials were synthesized by sol-gel method.The in-situ dissolution of Fe metal nanoparticles on the surface of RPLaSrFeO_4-δ matrix with good redox stability was discussed,and the performance of CO₂ electrolysis was studied.The specific operation is La_0.5Sr_0.5FeO_3δ reduction treatment can be converted into RPLaSrFeO_4-δ and metal Fe.X-ray diffractometer（XRD）,transmission electron microscopy（TEM）,energy spectroscopy（EDS）and other techniques were used to characterize the precipitation of metallic Fe nanoparticles.Through electrical conductivity,photoelectron spectroscopy（XPS）,gas adsorption（CO₂-TPD）and other tests,it is found that the precipitation of metallic Fe improves the catalytic ability of the electrode powder to CO₂.The results of electrolysis of CO₂ at 800℃ show that the current density obtained at 1.5 V working voltage is1270 mA cm-2,which is about 60%higher than the performance of-780 mA cm-2 of the RPLSF cathode material;at 800℃,1.0 V the polarization resistance of the FeRPLSF cathode is 0.25 Ω cm²,which is significantly lower than the 0.72 Ω cm² of RPLSF.The Faraday efficiency of the electrolysis cell for CO₂ electrolysis can reach more than 90%.It shows that the Fe nanoparticles dissolved in situ increase the catalytic active sites and improve the electrocatalytic performance of the electrode in the electrolysis of CO₂.Secondly,the cathode material RPLaSrFeO_4-δ of the electrolytic cell is doped with low-valence Ni element with high catalytic activity,and the structure of the material is controlled by doping and substitution,and its performance under reversible atmosphere is studied.With the doping of Ni element,the conductivity has been significantly improved.（1:1）The impedance spectrum of a symmetrical battery with a CO/CO₂ mixed atmosphere shows that the increase of Ni content is beneficial to reduce the polarization resistance of the electrode,and the performance is best when the doping amount is 0.1.Through the polarization impedance analysis of different CO/CO₂ mixed atmospheres,the reaction mechanism of the electrode surface under the reversible atmosphere is analyzed.It shows that the regulation of Ni doping can successfully improve the electrode performance.