Study On The Electrocatalytic Performance Of Alkaline Earth Metal Ion Doped Pr_0.94BaCo₂O_5+δ

Solid oxide cell(SOFC)is a type of all-solid-state power generation device that can directly convert chemical energy into electrical energy efficiently and environmentally,which is playing an increasingly important role in alleviating the energy crisis and environmental pollution.However,the commercialization of SOFC technology is hampered by high costs and limited system life due to high operating temperatures(850-1000℃).Thus,it is urgent to reduce the operating temperature of SOFC to the intermediate-temperature range(500-750℃).However,the decrease in operating temperature is always accompanied by a sharp increase in the electrode polarization resistance,leading to a deterioration in the performance ofthe entire cell.Therefore,efficient and stable electrode materials are to be developed at low and medium temperatures,and the electrochemical properties of the cathode determine its output performance.The main focus of this paper is to investigate the main factors affecting the catalytic activity and stability of cathodes using a combination of experimental and theoretical calculations on chalcogenide materials to further develop potential SOFC cathode materials.In this thesis,the Pr0.94Ba1-xSrxCo2O5-δ(x=0-0.5)perovskite oxide doped with Sr2+ at the A position was synthesized by glycine-nitrate combustion method,and the crystal structure and oxygen reduction reaction activity of perovskites were explored.The experimental results show that the doping amount of Sr increases and the Pr0.94Ba1-xSrxCo2O5+δ(x=0-0.5)gradually changes from the tetragonal phase to the cubic phase.Among them,Pr0.94Ba1-xSrxCo2O5+δ(PBS0.3CO)has good oxygen reduction reaction activity.Its polarization resistance is 0.031 Ωcm2 at 700℃;H2-fueled anode-supported Ni-YSZ|YSZ|CGO|PBS0.3CO fuel cell has a maximum power density of 1077 m W cm-2 and it also exhibits excellent stability(700℃～130 h).At the same time,the first-principles calculation results show that enabling a metal-like conduction nature and effectively improve the adsorption energy of oxygen molecules.And PBS0.3CO has good ORR reactivity,which is consistent with the experimental results.Perovskite oxide doped with a series of dual alkaline earth element-substituted perovskites Pr0.94Ba1-2xSnCaxCo2O5+δ(x=0-0.3)was successfully synthesized.The effect of the alkaline soil doping at position A on its electrochemical properties was systematically studied.The results showed that Pr0.94Ba0.6Sr0.2Ca0.2Co2O5+δ had the best oxygen reduction reaction activity among all components.At 800℃ the conductivity of Pr0.94Ba0.6Sr0.2Ca0.2Co2O5+δ reaches 560 S cm-1 and The oxygen surface exchange coefficient(kchem)is 6.61×10-3 cm s-1.Relaxation time distribution(DRT)analysis showed that the doping of Sr and Ca increased the rate of charge transfer and oxygen surface exchange.The Pr0.94Ba0.6Sr0.2Ca0.2Co2O5+δ cathode exhibited the highest electrocatalytic activity,with a polarization resistance value of0.025 Ω cm2 at 700℃.The anodesupported fuel cell based on Pr0.94Ba0.6Sr0.2Ca0.2Co2O5+δ cathode has a maximum power density of 1194 m W cm-2 while exhibiting excellent stability(700℃,～160 h).At the same time,the firstprinciples calculation results show that enabling a metal-like conduction nature and effectively improve the adsorption energy of oxygen molecules.It was shown that Pr0.94Ba0.6Sr0.2Ca0.2Co2O5+δhad great oxygen reduction reaction activity,which is consistent with the experimental results.