Meilin Liu holding a button solid oxide fuel cell
Solid oxide fuel cell (SOFC) performs an electrochemical conversion to electricity by oxidizing a fuel. The high efficiency, stability, low emissions and platinum free low costs make the cell very attractive. However, the biggest motivation for use is its ability to accept a wide variety of fuels, such as gasoline, diesel, jet fuel, biofuels, and now coal.
Burning coal is still the world's number one source of energy. However, the continual burning is not doing the environment any favors. However, converting coal to coal gas for use in a SOFC may be the cleanest use of the rock according to Georgia Institute of Technology professor and director of the Center for Innovative Fuel Cell and Battery Technologies Meilin Liu. Currently carbon based fuels used in a SOFC, like coal gas and propane, will clog the anode within minutes of operation. SOFC anodes are made from nickel (Ni) and yttria stabilized zirconia (YSZ), together forming a thick layer that is often used as structural support of the cell itself. When using carbon fuels on the Ni-YSZ anode, deposits of carbon form and stop the reaction of the cell called "choking."
Georgia Tech lead a team of researchers to create a nanostructure of barium oxide on the anodes. The structure absorbs water as a component of a chemical reaction that oxidizes the carbon produced in the SOFC's operation, which keeps the nickel electrode clean. When the coal gas hits the barium oxide layer it cuts the gas into protons and hydroxide (OH) ions. The OH ions combine with the carbon deposits creating COH. The COH then dissociates into CO and H and oxidized to power the fuel cell. The output of the cell is CO2 and H2O. Half of the CO2 is recycled to gasify coal into coal gas. The prototypes of the cell have been demonstrated to operate without buildup for hundreds of hours. And similar results were seen with using propane as the fuel.
The next step for the team is to lower the operating temperature of the SOFC, currently at 850°C. SOFCs predominately operate at high temperatures, which is the main reason for cost. Until the self-cleaning development, lowering the temperature made the carbon build up even worse.
Yes, the cell still produces CO2. However, Liu notes that the CO2 from this process is the purest form of the gas. Which makes the capturing and storage less expensive since it does not require separation and purification steps.
Eavesdropper
(Georgia Tech's team also includes researchers from Brookhaven National Laboratory, the New Jersey Institute of Technology and Oak Ridge National Laboratory. The effort is sponsored by U.S. Department of Energy's Office of Basic Energy Sciences.)
