In this experimental project the student will characterize electrochemically a number advanced thin film cathodes for use in solid oxide fuel cells. The student will develop a general understanding of fuel cells materials and solid state electrochemistry.
1. Electronic conductivity
The electronic conductivity of the thin films as a function of temperature (400-800 °C) and oxygen partial pressure (pO2) will be measured by using two- or four-probe DC method. The pO2 (1-10-2 atm) will be adjusted by mixing O2 and N2 with mass flow controllers. Taking four-probe DC method as an example, four leads including two current leads and two voltage probes will be used to create current and probe voltage. Both the created current and corresponding voltage will be recorded by VSP (an electrochemical workstation, BioLogic Science Instruments).
2. Electrochemical impedance spectroscopy
The electrochemical impedance spectroscopy of thin film cathodes with the symmetrical configuration will be measured in the frequency range of 10-2 to 106 Hz from 400 to 800 °C under different pO2 by using the VSP. Current collectors with different materials and configurations will also be considered.
3. Open circuit voltage and power density
The electrochemical performance of thin film cathodes will be evaluated in the anode supported single cells consisting of thin film cathodes/SDC/YSZ/NiO+YSZ and compared with cells with thick porous cathodes. To obtain a fuel cell reactor, the cell will be sealed to one end of a quartz or aluminum tube by using silver or ceramic. Humidified hydrogen (3% H2O) will be fed into the anode at a flow rate of 80 ml min?1, while oxygen or air will be fed to the cathode. The open circuit voltage and power density will also be recorded by VSP.
1. Familiarize with Electrochemical Characterization, two and four-probe DC methods and EIS
2. Assess performance of fuel cells as a function of temperature and oxygen partial pressure