Thickness-electrochemical Properties Of Reversible Solid Oxide Cell Thin Film Oxygen Electrode LSCF-10GDC

Reversible solid oxide cell（R-SOC）has been widely studied for its characteristics of direct electrochemical conversion of chemical energy of fuel into electric energy and electric energy into chemical energy,and for its advantages of high fuel efficiency,environmental friendliness and energy hydrogen storage.Reducing operating temperature of SOC can solve the problems of high cost and high sealing difficulty caused by high temperature,which is one of the research interests.Improving the catalytic activity of electrodes and reducing the thickness of electrolytes or using electrolytes with higher ionic conductivity are effective ways to solve the problems such as the increase of ohmic impedance and the decrease of catalytic activity of electrodes caused by the decrease of operating temperature.As a rate-determining step,it is very important to improve the catalytic activity of oxygen electrode.Compared with the pure electron conductor La_0.8Sr_0.2Mn O_3-δ（LSM）oxygen electrode,the mixed ion-electron conductor La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ（LSCF）oxygen electrode has higher catalytic activity to oxygen,which makes it obviously have greater advantages at intermediate and low temperature.But LSCF-based materials react with conventional Y_0.16Zr_0.84O_2-δ（YSZ）electrolytes at lower temperatures.Therefore,it is necessary to prepare a GDC barrier layer between YSZ electrolyte and LSCF-based oxygen electrode to prevent the reaction between them and improve the thermal matching.In this paper,prepared and optimized the Ce_0.8Gd_0.2O_1.9（20GDC）barrier layer and controlled the thickness of La_0.6Sr_0.4Co_0.2Fe_0.8-Ce_0.9Gd_0.1O_1.95（LSCF-10GDC）composite oxygen electrode by screen printing to improve its electrochemical performance.The main conclusions are as follows:（1）20GDC powder were prepared by sol-gel method,then prepared the barrier layer.The effects of different calcined temperatures of powder and different calcined temperatures of 20GDC barrier layer on electrical properties were investigated.The results show that,compared with 800℃,20GDC powder calcined at 600℃has higher specific surface area and worse combination with YSZ electrolyte.Compared with 1150℃and1350℃,when the sintering temperature of 20GDC barrier layer is 1250℃,the diffusion between Ce with Zr elements and interfacial binding reach a better balance.Preparation of Ni O-YSZ||YSZ||20GDC||LSCF-10GDC single cell have the best electrochemical performance,under 750℃,with a minimum of ohmic impedance,the maximal power density of 894 m W·cm^–2.（2）To investigate the effect of the thickness of LSCF-10GDC oxygen electrode on its electrochemical performance.By fitting the EIS impedance and DRT analysis of symmetrical oxygen electrode cells,it is found that the thickness of oxygen electrode has a significant effect on the adsorption/desorption-dissociation process of oxygen molecules.With the increase of oxygen electrode thickness,its hindrance to oxygen diffusion process becomes stronger.Compared with 5μm and 22μm,the lowest polarization impedance is0.0343Ω·cm²（750℃）when the oxygen electrode thickness is 12μm.For the test of different thickness of oxygen electrode Ni O-YSZ||YSZ||20GDC||LSCF-10GDC single cells found that the single cell with oxygen electrode thickness of 12μm have optimal performance.In SOFC mode,with 3 vol.%H₂O+97 vol.%H₂ as fuel gas and static air as oxidant,the polarization impedance of single cell is 0.24Ω·cm² and the maximum power density is 1098 m W·cm^-2 at 800℃.In SOEC mode,with 70 vol.%CO₂+30 vol.%H₂（3vol.%H₂O）as fuel gas,the polarization impedance is 0.342Ω·cm² at 800℃,and the current density is 1.397 A·cm^-2 at 1.5 V...