CBE PhD Dissertation Defense | “Surface Modification of Solid Oxide Cell Electrodes to Improve the Electrochemical Performance”

Abstract: 

“Solid Oxide Fuel Cells are high temperature, solid-state, electrochemical devices that can convert fuels into electricity or produce fuels from excess electricity. Oxygen is reduced at the cathode to oxygen ions which move through the ceramic to the anode. These oxygen ions are used to oxidize fuels at the anode compartment, producing heat and electrons that will move through an external circuit to produce power.
At the cathode the sluggish oxygen reduction kinetics impede the performance of the electrode. A common approach to enhance the cathode performance is infiltration. Often the performance of a cathode is enhanced after the addition of a variety of metal-oxide materials. The common claim is that the infiltrated materials enhance catalytic activity or conductivity. With infiltration however, it is impossible to control for changes in surface area or conductivity. Atomic Layer Deposition (ALD) was employed to change the surface chemistry of the electrode, without changing the conductivity, or surface area of the electrode.
Perovskite anodes are of interest due to their resistance to many of the issues that plague Ni-cermet (ceramic metal) anode. Their catalytic activity is often lacking, and as such a variety of methods are employed to enhance this. The most efficient approach is surface modification which allows for increases in activity with minimal metal loadings. ALD was employed to deposit highly disperse oxidation catalysts in order to minimize the metal loadings while maximizing performance.

At the Ni-cermet anode, undesirable reactions, such as carbon fiber formation and Ni oxidation to NiO, limit the lifetime of the electrode. Surface modification approaches are often employed to protect the Ni surface against these processes. We investigated the use of CeO2 ALD to overcome these challenges.

Perovskites with exclusively 2 + cations (Ba and Sr) in the A-site and Fe in the B-site have recently exhibited great performance as SOFC anodes. The reasoning behind the high catalytic activity of these anodes has not been thoroughly studied. To elucidate the origin of the high activity of these anodes, the performance and thermodynamics of Ba0.5Sr0.5FeO3 (BSF) anodes was investigated.”