Design and fabricate multifunctional complex oxide thin films and heterostructures with optimized multifunctionalities

The Symmetric Solid Oxide Fuel Cell (SSOFCs) LBCO/GDC/LBCO is fabricated by Pulsed Laser Deposition technique. The cell can provide an Open Circuit Voltage (OCV) about 800mV at the temperature low than 400°C. The SCC shows typical thermal activation behavior. The two-probe EIS of single layer LBCO thin film in hydrogen shows that the activation energy of polarization resistance is 0.1eV. The experiments demonstrated the feasibility of new type of Low Temperature SSOFC based on the double perovskite material. Giant resistance switching phenomena were systematically studied by monitoring the resistance changes of the highly epitaxial LaBaCo2O5.5+δ (LBCO) on LaAlO3 (001) under the flow switches from H 2 4%_N296% to pure CO2. The LBCO thin film is an excellent electrical conductor under CO2 ambient at high temperature and shows resistance response as low as 638K. The Electrical Impedance Spectroscopy (EIS) studies on the LBCO/GDC/LBCO symmetric cell reveal that the activation energy of surface exchange coefficient is 1.47eV and 0.83eV in different temperature range. These excellent catalytic properties make the LBCO a candidacy for the CO2 dissociation and chemical sensor. The symmetric PrBaCO2O5.5+δ (PBCO)/YSZ/PBCO cell is designed and fabricated for the investigation of the catalytic nature and reaction dynamics of CO2 on the PBCO surfaces. The Electrochemical Impedance Spectroscopy was employed to trigger the CO2 reaction behavior on the PBCO electrode. The symmetric equivalent circuit cell model fitting reveals that the surface resistance of the CO2 on PBCO was found to be 20 Ωcm2 and the maximum surface exchange coefficient kchem was 5.76e-5 cm/s at 1147K. The negative activation energy of kchem is derived from the Arrhenius plot at the high temperature range for the CO2 reaction. Furthermore, the doping effect studies for the catalysis properties of LnBCo2O5.5+δ (Ln=La, Pr, Eu and Er) indicate that the polarization resistance at 1173K is in the order of Pr< La < Eu< Er. This result demonstrates that CO2 surface catalysis on the LnBCO electrode material is highly dependent on the A-site cation's radius and the oxygen diffusivity of the double perovskite structures. The LnBCO electrodes can work for CO2 splitting from 973K.