Preparation And Performance Of CeO₂-based Composite Cathode Materials For High Temperature H₂O/CO₂ Co-electrolysis

High temperature H₂O/CO₂ co-electrolysis technology?High Temperature Co-electrolysis,HTCE?uses nuclear or renewable energy to convert H₂O and CO₂ into syngas through electrochemical reactions.HTCE is an interesting topic in the international energy field.The core device of HTCE is solid oxide electrolysis cell?SOEC?.In this work,the research focused on the key issues associated with its ceria-based composite cathode materials.The optimum composition of Ni/GDC was studied.Also,the doping amount of Cu in NiCu/GDC electrode was analyzed.And finally single cells were prepared to evaluate their performance.The major results are shown as follows:?1?The ratio between Ni and GDC in the Ni/gadolinia doped ceria?GDC?cermet electrode plays a decisive role for the electrode performance.In this work,the GDC powder was first synthesized at around 200oC by the citrate-nitrate combustion method,and then it was mechanically mixed with commercial NiO powder in different proportions.After sintering and reducing,the composite cathodes were tested to explore the optimum Ni to GDC used as the cathode of SOEC in HTCE.The results showed that,when the NiO content was 55 wt%,the reduced electrode's conductivity was up to 1232.05 S/cm at 800oC,about three times more than that with 50 wt%NiO doping,and the contents of Ni has exceeded Penetration Threshold.In addition,in the Ni-GDC/Yttria-stabilized zirconia?YSZ?/Ni-GDC structured symmetric cells with different Ni contents,the polarized impedance of this composite cathode,with NiO content of 55 wt%,was 0.534?·cm² at 800oC under reducing atmophere,showing the best performance.?2?Alloy ceramic electrode can effectively improve the electrode performance by incorporating metals with excellent characteristics.Synthesized GDC and NiCuO powder with different doping amount of Cu were mixed.After sintering and reducing,the composite cathodes were tested to explore the optimal amount of Cu in NiCu/GDC cathode of SOEC in HTCE.The results showed that,Ni_0.90Cu_0.10/GDC had the highest conductivity of 1376.27 S/cm at 800oC under reducing atmosphere,11.71%higher than that of Ni/GDC electrode with 55 wt%NiO content.The polarized impedance of the Ni_0.90Cu_0.10-GDC/YSZ/Ni_0.90Cu_0.10-GDC structured symmetric cells was 0.267?·cm² at800oC under reducing atmophere,better performance with decreased polarized impedance by 50%than that of Ni-GDC/YSZ/Ni-GDC structured symmetric cells without any Cu doping.?3?The performance of electrolyte-supported single cells assembled with the cathode studied in this work was reliable for high temperature co-electrolysis.Under the electrolysis conditions of 800oC and 1.6 V,the current density could reach 337.05mA/cm²,and the average area specific resistance?ASR?was 2.620?·cm² at low current density and 1.895?·cm² at middle current density.The energy conversion efficiency of SOEC before and after 10 runs of co-electrolysis cycles was 91.37%and 89.93%respectively,showing stable performance without significant decay.The study of ceria-based composite cathode materials in this work provides a guideline to develop new cathode materials for high temperature co-electrolysis.