Co-extruded triple layer hollow fiber solid oxide fuel cell using methane

Abstract

Solid oxide fuel cell (SOFC) is one of the most promising fuel cells and it has been developed extensively in recent years. However, carbon deposition on the anode site is the main issue of this system when methane is used as the fuel. Therefore, the objective of the research is to develop a methane-fueled micro tubular solid oxide fuel cell (MT-SOFC) with excellent carbon resistant property. In the first phase of this work, triple layer hollow fiber, which consisted of anode which used nickel oxide (NiO) and yttria stabilized zirconia (YSZ), anode functional layer (AFL) also made of NiO and YSZ, and electrolyte from YSZ, was fabricated via phase inversion-based coextrusion/ co-sintering technique with varied fabrication parameters (i.e. ratio NiO/YSZ in the AFL and sintering temperature) and such triple layer design that has been previously reported is able to possess several advantages such as high power output and high thermal expansion coefficient. Further, the cell was tested using methane gas as fuel. The hollow fiber with the ratio of 2:8 of NiO to YSZ of AFL suspension shows crack-free properties. After sintering between 1400 oC and 1500 °C, the hollow fiber recorded an increase from 110.1 to 130 MPa on three-point bending tests and 1.26×10-5 to 4.6×10-6 mol m-2 s-2 Pa-1 for gas tightness tests. The maximum power densities obtained at 800 °C were 0.8 W/cm2. In the second stage of the study, the prolonged operation of the SOFC was done using methane fuel to observe the carbon deposition phenomenon. The fuel cell showed significant reduction of power density from 0.8 W/cm2 at 800 °C to 0.2 W/cm2 after 90 min. In the third stage of the work, ceria gadolinium oxide (CGO) was incorporated in the anode suspension to increase the resistance towards carbon poisoning. With the addition of 3wt.% of CGO at the anode layer, the performance degradation was reduced to only 50% from the initial power density after 90 min, in comparison to the cell without CGO (the reduction of 75% after 90 min), although the initial power density of the modified one was slight lower (0.4 W/cm2) than the unmodified cell (0.8 W/cm2). It was shown that the CGO able to reduce the degradation of the cell under methane as fuel.