Novel structured anode-supported solid oxide fuel cells with porous GDC interlayers

Abstract

In this study, the effects of porous GDC interlayer(s) addition into NiO-YSZ anode functional layer on the performance of anode supported solid oxide fuel cells are experimentally studied. The number and porosity of GDC interlayer(s) are also considered in the study. For this purpose, firstly three different NiO-YSZ anode supported cells having various NiO-YSZ anode functional thicknesses are fabricated by tape casting and screen printing methods as base cases. Other cells are also fabricated similarly by adding 1–3 GDC interlayer(s) having different porosities into anode functional layer, keeping the total anode functional layer thickness as the same. The porosity of the interlayer is controlled by changing the pore former content in the tape casting solution of GDC interlayer from 5 wt % to 20 wt%. Thus, fifteen anode supported cells in total are fabricated and tested. All cells have 16 cm2 active area and are characterized by performance and impedance tests as well as microstructural analyses. The results reveal that it is possible to improve the cell performance by GDC interlayer addition. The base cell prepared with three NiO-YSZ anode functional layers provides only 0.283 Wcm-2 peak power density at 800 °C, while the modified cell, where NiO-YSZ layer in the middle is substituted by a GDC interlayer prepared with 15 wt % pore former, exhibits 0.582 Wcm-2 maximum power density at the same operating conditions. Furthermore, the cell performance is found to decrease with increasing the number of GDC interlayer, while it is shown to increase with the pore former content up to 15 wt %. The variations in the cell performance are due to changes in the ohmic, charge transfer and diffusion resistances as confirmed by impedance analyses as a result of resultant anode functional layer microstructure depending on the cell design observed by scanning electron microscope.