The Georgia Tech-led research team has devised a self-cleaning method utilizing barium oxide nanoparticles. The method could make coal gas to power solid oxide fuel cells directly at operating temperatures as minimum as 750°C.
The method could offer a highly effective and cleaner option to traditional power facilities using coal. According to the scientists, a combination of fuel cells and gas turbines could convert 80% of the energy produced from traditional coal-fired facilities. However, to achieve that conversion efficiency, the fuel cells should operate for longer time on coal gas, which now allows the anodes to operate for 30 minutes.
The research team has developed a carbon removal system that utilizes a vapor deposition method to deposit the barium oxide nanoparticles over the electrode produced from nickel (Ni) and yttria-stabilized zirconia (YSZ), a ceramic material. The nanoparticles with sizes ranging between 10 and 100 nm create islands on the nickel, which allows the flow of electrons through the electrode surface.
The water vapor added to the coal gas flow is adsorbed by the barium oxide and dissociated into hydroxide (OH) and protons ions. The OH ions, which move towards the surface of the nickel, form the intermediate COH by combining with the carbon atom deposits on the surface. The COH is then dissociated into hydrogen and carbon monoxide, which are used to power the fuel cells through oxidation, eventually generating water and CO2. Nearly 50% of the CO2 is then reused for the gasification of coal to produce coal gas.
The scientists also investigated the utilization of propane as a power source for solid oxide fuel cells utilizing the Ni-YSZ. This eliminates the introduction of water vapor as water is produced by the oxidation of the hydrogen molecule in the propane. The normal operating temperatures of solid oxide fuel cells are more than 850°C. One of the objectives of the research work is to decrease the operating temperatures down to 700°C or 750°C, which enables the utilization of cheaper materials for interlinks and other vital components.
The formation of barium oxide structures does not need additional methods and can be performed as part of the production processes for traditional anodes. The scientists have successfully evaluated their method for a 100 h and saw no proof of carbon formation. The actual challenge in front of them is to assess the system’s durability for fuel cells, which are developed to function for five years. They should also investigate the risk of potential fuel contaminants on the Ni-YSZ electrode.
The Ni-YSZ anodes developed in the process are suitable for standard solid oxide fuel cells, which are under production for automotive, home power production and commercial electricity production.