Degradation of Solid Oxide Fuel Cell Using Thin Film Electrodes Fueled By Carbon Monoxide-Hydrogen Syngas

Abstract

According to the recent development trend of the smart farm industry, solid oxide fuel cells are emerging as a sustainable power source due to their high fuel efficiency and fuel flexibility which includes carbon fuels such as carbon monoxide. This study conducted a series of experiments to secure an operation strategy for a solid oxide fuel cell operating at the intermediate temperature of 650~800C. Although it is known that when a fuel cell is operated using carbon-based fuel at an intermediate temperature under 800C, fatal degradation occurs due to carbon coking, widely used commercial fuel cell stacks were manufactured not to exceed that temperature. To simulate a commercial fuel cell stack, the experiment was conducted in the commercial operating temperature range, and nickel-yttria stabilized zirconia was used as anode material. Additionally, ceria-based anode material was applied, and compared its single-cell performance with that of the yttria-based anode material. Carbon monoxide-hydrogen mixed fuel, which can be produced through torrefaction and fuelization from agricultural by-products, was supplied. To this end, a YSZ-based electrolyte-supported cell using Ni-YSZ/Ni-GDC and LSCF-GDC as anode and cathode materials, respectively, was fabricated by the sputtering method. The cell performance and degradation phenomenon were measured under the two temperature ranges and two fuel supply conditions. For structural analysis, FE-SEM and FIB-SEM methods were conducted, and techniques such as the i-V-P curve, EIS, and DRT were used for their electrochemical analysis. The relationship between the nano-scaled structural change caused by the carbon coking phenomenon and the cell performance was derived. Especially, EDS mapping and XPS analyses were conducted to quantify the carbon coking phenomenon. Through this, the degradation mechanism mainly caused by carbon coking was analyzed when syngas was used as a fuel. The optimal operating condition for durable fuel cell performance was confirmed for the stack-sized operation in the smart farm industry.