Solid Oxide Fuel Cells

Solid Oxide Fuel Cells (SOFCs) based on the yttria-stabilized zirconia (YSZ) electrolyte are ceramic devices that operate at very high temperature (800 - 1000C). Because of the high operating temperature, this type of fuel cells does not require expensive catalysts, additional humidification and fuel reforming equipment, which are used in Polymer Electrolyte Membrane Fuel Cells (PEM FCs). SOFCs are considered promising for large power plants and for industrial applications, particularly for combined power and heat generation.

One of the most important materials problems to be addressed in the development of SOFCs is the fuel electrode. While the very significant potential for direct electrochemical oxidation (DECO) of hydrocarbon fuels has recently been demonstrated the underpinning physical and chemical processes are not well understood and characterized at a fundamental level. Concerted theoretical and experimental approach to isolate and elucidate the fundamental processes and their interactions for DECO in SOFCs might provide improved understanding and modeling capabilities for accelerating the development of new fuel cell technology. Our objectives are following:

  • Provide detailed membrane/electrode assembly models that quantify the influence of electrode/electrolyte microstructure, composition, and materials properties for current and potential new SOFC materials
  • Understand fundamental chemical processes such as elementary charge-exchange kinetics, internal CPOX/reform/shift chemistry, ion and species transport, homogeneous chemistry and deposit formation, etc.
  • Develop predictive models and simulation tools, including critical chemistry and transport sub-models, for evaluating fuels and fuel blends in high performance DECO. Atomistic Level Modeling of Catalysis and Other Processes

    Atomistic Level Modeling of Catalysis and Other Processes

    Recent research on DECO of small hydrocarbons has sought to achieve good electrical and ionic conductivity while avoiding coke formation. As we consider more complex organic feedstocks, it becomes important to consider introducing catalytic properties into the electrocatalysts that might achieve the desired reactions more selectively with lower barriers at lower temperature, while retaining insensitivity to carbon deposits and good electrical and ion conductivities. For this reason our project includes as an essential component, the atomistic-level characterization of the mechanisms underlying the chemical transformations and the transport properties. There are several atomistic components to this project, which we seek to understand:

  • Geometric structure of the metal-doped oxide
  • Reaction mechanisms governing the chemical transformations of the feedstock to products
  • Barriers and rates for these chemical processes
  • Rates for ion migration processes
  • Electrical conductivity

    We are developing an improved understanding of mechanisms from the theory, which will be used to suggest new combinations of metals and oxides and then use computational approaches to rapidly screen a number of potential choices. The best candidates will be considered for experimental validation and refinement. For the best candidates the atomistic theory will be used to predict kinetics (barrier heights and pre-exponential factors) that can be integrated into the chemical-kinetics models to simulate the complex processes of the fuel cell.

    Figure 1: Schematic of the computational domain and microscale processes considered in the triple-phase boundary model.

    Personnel: Dr. Boris Merinov and Dr. Adri van Duin.