Enhanced Performance Of Solid Oxide Electrolysis Cells For High-temperature CO₂ Electrolysis Through Modification Of Eathode

High temperature Solid Oxide Electrolytic Cell(SOEC)can be used to synthesize hydrocarbon fuels when fed with CO₂ and/or H₂O,as is considered as a positive solution for energy crisis and environmental pollution.Cathode,where the main electrolytic reactions happen,is the most important component that will determine the performance of SOEC.Therefore,in this work,oxygen-ion conducting SOECs based on 8YSZ electrolyte support were prepared using high temperature redox-stable perovskite La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-?(LSCM)and fluorite Nb Ti_0.5Ni_0.5O₄(NTNO)as cathode materials,respectively.The influences of cathode modification on the performance of cathode materials and corresponding SOECs were investigated.Results showed that nano V₂O₅catalyst particles can be synthesized on the LSCM cathode by dipping NH₄VO₃solution.With the loading of 2 wt.%nano V₂O₅,the catalytic activity of LSCM cathode can be enhanced and the polarization resistance(R_P)was reduced significantly.In particular,in pure hydrogen under 800?,R_P of the cathode reduced from 2.6?cm² to1.2?cm² after modification.For electrolysis of CO₂,the current density and faradic efficiency of SOEC with modified cathode enhanced by 30%and 40%,respectively,under 800? and working voltage of 1.2?2V,compared with the unmodified one.The Nb Ti_0.4Mn_0.1Ni_0.5O₄(NTMNO)and Nb Ti_0.4Cr_0.1Ni_0.5O₄(NTCNO)cathodes were prepared by Ti-site doping of NTNO with active Mn and Cr elements.Results showed that large amount of evenly distributed nano Ni catalyst particle can be precipitated on the surface of NTNO particles after reduction under 800?.The ionic-conductivity and adsorption of CO₂ can be enhanced by high concentration of oxygen vacancy after doping modification of NTNO,and the catalysis reactivity was improved accordingly.With doping of Cr and Mn,the R_P reduced from 2.4?cm² of unmodified NTNO cathode to 1.6?cm² and 1.3?cm²,respectively,in pure hydrogen under 800?.The faradic efficiency of SOECs with NTCNO and NTMNO cathodes for electrolysis of CO₂ can reach 92%and 96%,respectively,being much higher than that of unmodified one(55%),with a working voltage of 1.0?1.8V at 800?.