Structural characteristics of pore former assisted cathode layer in micro-tubular solid oxide fuel cell

Abstract

The cathode performance of solid oxide fuel cell (SOFC) depends substantially on its surface area, porosity and microstructure, and therefore the processing method is very important in determining cathode performance. By improving the structural characteristics of the layer, the cathode performance during fuel cell operation can be fully maximized. This study aims to improve the porosity and pore structure of the cathode deposited layer of micro-tubular SOFC (MT-SOFC) by inducing pores with pore formers. Three types of pore formers have been used to investigate the formation of induced pores in the cathode layer of SOFC, which are polyether ether ketone (PEEK), corn starch and graphite. Each pore former chosen in this study possesses different particle geometry in order to produce distinct pore geometry in the cathode layer. The cathode layer was brush painted on an anode/electrolyte dual layer support hollow fibre that had been previously sintered at 1500°C for 12 hours. The coated cathode consists of three layered coats, with functional layer as the first two layers followed by a current collector layer on the last coat. After the deposition of cathode layer, it is sintered at 1200°C for 5 hours. The study divides the characterization into three main parts; pore former geometry identification, pore former behavior in lanthanum strontium cobalt ferrite (LSCF) powder and pore former in LSCF as solid oxide layer. PEEK was able to produce pores that promote both fine microstructures for triple phase boundary generation and porous structure for efficient diffusion of gases. The increase in pore former loading has increased the porosity and decreased the grain size, but at the expense of decreasing mechanical strength of the fuel cell.