Molybdenum-regulated Cobalt-based Perovskite Electrodes For Symmetric Solid Oxide Batterie

To address the high consumption and serious pollution of traditional fossil energy sources,there is a growing demand for renewable green energy sources and advanced energy development technologies.Solid oxide cells（SOCs）offer a promising solution,as they can generate electricity using clean energy such as H₂ in solid oxide fuel cells（SOFCs）mode and can use electric energy to convert H₂O and CO₂ into chemical energy for storage in solid oxide electrolytic cells（SOECs）mode.Symmetrical solid oxide cells（SSOCs）have become a research hotspot in this field due to their simple fabrication,improved cell compatibility and avoided sulfur poisoning and carbon deposition.Currently Co-based perovskites are one of the most promising electrode materials due to their good oxygen reduction reaction activity,but are still limited by low catalytic activity and poor stability.Therefore,this thesis takes Co-based perovskite as the research object,and uses Mo element to carry out modification strategies such as B-site doping,structural modulation and defect engineering,which improved the structural stability and catalytic activity of SSOCs electrodes.First,Ba_0.5Sr_0.5(Co_0.8Fe_0.2)_0.8Mo_0.2O_3-δ（BSCFM）with a pure cubic structure was obtained by Mo doping at the B-site.Compared with the pre-doping,BSCFM shows better reduction stability,structural stability,and thermal stability.In terms of catalytic activity,BSCFM|LSGM|BSCFM has an area specific polarization resistance of only 0.064Ω·cm² and a maximum power density of 1225 m W·cm^-2 at 800°C in wet H₂,and has maintained a stable output power during nearly 100 hours of long-term operation.Thus,Mo doping improves the stability and catalytic activity of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ,making BSCFM a promising symmetric electrode material.Secondly,the effect of Mo concentration on Sr₂Fe Co_1-xMo_xO_6-δ（SFCM_x,x=0.1,0.3,0.5）electrode material was further investigated based on Mo doping.With the increase of Mo doping concentration,perovskite slowly transforms into a simple cubic structure,which improves the stability of the crystal structure,but at the same time is detrimental to the generation of vacancy defects.the maximum current density of the SFCM_0.3 symmetric electrolytic cell for the electrolysis of H₂O can reach 0.924 A·cm^-2 at 800°C and 2 V,which is46%and 25%higher than SFCM_0.1and SFCM_0.5 respectively.The area specific polarization resistance of SFCM_0.3 is 0.72Ω·cm² at 800°C and OCV,which is smaller than that of SFCM_0.1 and SFCM_0.5.However,SFCM_0.5 has a more stable working state of electrolytic water than SFCM_0.1 and SFCM_0.5,and has almost no decay in more than 60 hours of testing.Cell performance tests were also performed for all three materials in H₂/H₂O and the results showed that they all had good reversibility.Thus,adjusting the concentration of Mo in SFCM_x can improve the stability and catalytic activity of the electrode materials.Finally,to solve the problem that Mo doping would introduce new impurities,Ba Mo O₄was removed by alkali treatment and Mo vacancies were introduced.The results show that the Mo vacancies provided abundant CO₂ adsorption reaction sites and promoted the electrocatalytic process,and has good stability under high temperature CO₂ conditions.The maximum current density of Pr_0.5Ba_0.5(Mn_0.85Co_0.15)_0.9Mo_0.1-xO₃(PBMCM_0.1-x)symmetric cell with Mo vacancies can reach 1548 m A·cm^-2 at 800°C 2.0 V,and the polarization resistance is0.56Ω·cm² at 800°C 1.5 V,which is better than that of the symmetrical cell before doping and alkali treatment.During long-term operation,the current density of PBMCM_0.1-xsymmetrical cell has no obvious attenuation and has good cell durability.Therefore,the alkali treatment method can remove the impurities caused by Mo doping and create Mo vacancies,so that the PBMCM_0.1-x symmetric cell can electrolyze CO₂ stably and efficiently.