| Solid oxide fuel cells(SOFC)are considered as one of the most promising technologies for clean energy production due to their high efficiency,high power density and flexible fuel selectivity.Traditional SOFCs need to operate at high temperatures(～1000℃).Reducing the operating temperature of SOFCs from the traditional 1000℃to the medium temperature range of 500-700℃ can extend the life of battery materials,reduce operating costs,and expand the selection of materials.Double perovskite oxide is a promising cathode material with high electrocatalytic activity,fast oxygen ion mobility and controllable oxygen content.Therefore,this paper chooses PrBaCo2O5+δ as the research object to study the effect of A-site doping on the electrochemical performance.Because of the influence of anion doping on the structural stability and electronic structure,F-ion doping is proposed to improve the electrochemical performance.In this thesis,we first investigate the effect of the concentration of Pr in Pr1+xBa1xCo2O5+δ(P1+xB1-xCO)on the crystal structure and properties.The experimental results show that with the increase of Pr concentration,the conductivity of P1+xB1-xCO is obviously improved.At 700℃,P1.1B0.9CO showed the smallest polarization impedance(0.05 Ω cm2)and the maximum power density reached 0.81 W cm-2.At 700℃,P1.1B0.9CO showed excellent activities of oxygen precipitation(OER)and reduction(ORR).Based on the P1.1B0.9CO,Sr doping strategy was used to optimize the influence of electrochemical performance.The experimental results show that Sr doped with P1.1B0.9CO can obviously improve the conductivity of the material and reduce the polarization resistance of the material.The polarization resistance at 700℃ is only 0.027Ω cm2,and the maximum power density can reach 1.17 W cm-2.The OER and ORR activities of P1.1B0.9CO were significantly improved by effectively reducing overpotential and increasing current density.Finally,F-anion doping strategy was used to improve the electrochemical performance of P1.1B0.9CO.The experimental results show that the polarization impedance of Pr1.1Ba0.9Co2O5+δF0.1(P1.1B0.9COF0.1)cathode is 0.033 Ω cm2 at 700 ℃,and the output power density of the whole battery can reach 1.103W cm-2.The theoretical calculation shows that F-improves the dissociation of molecular oxygen and the desorption of oxygen atom by P1.1B0.9CO.Therefore,the P1.1B0.9COF0.1 electrode has improved ORR and OER activity in both SOEC and SOFC. |
