Study on porous LA0.8SR0.2GA0.8MG0.2O3-δ scaffold electrode and infiltration catalyst for solid oxide fuel cell

Abstract

Solid Oxide Fuel Cells (SOFCs) are attractive energy conversion devices for conversion of chemical fuels (hydrogen and oxygen molecules) directly into heat and electricity. The merits of SOFCS are high electric efficiency, low emission of pollutants and fuel flexibility due to high operation temperature. How-ever, the high operation temperature, which gives the merits for SOFCs, also is the cause of problems such as limitation selection of materials, thermal degradation of SOFC cell and stack compnents and oxidation of metal interconnect. These problems can be solved reducing SOFCs operation temperature. To achieve re-ducing operation temperature, both electrolyte loss and electrode polarization resistance should minimize at the intermediate temperature. Sr- and Ga-doped lanthanum gallate (LSGM) is considered to promising elec-trolyte due to its high oxygen ion conductivity and stability under SOFC operation condition. However, the LSGM seriously reacts with anode material and cathode material during cell fabrication and operation. In this thesis, LSGM is selected as an electrolyte material to reduce electrolyte loss and a scaffold electrode is proposed to avoid interfacial reaction between LSGM and electrode materials (anode catalyst and cathode catalyst). Firstly, fabrication procedure of the scaffold electrode is optimized and individually analyzed as an anode and a cathode. The scaffold electrode is fabricated via two different steps depending of firing temperature (high temperature and low temperature). The LSGM scaffold is formed on the dense LSGM electrolyte using screen printing method at high firing temperature in air atmosphere for 2 h. The connectivity and adhesion between porous LSGM scaffold and dense LSGM electrolyte improves with increasing firing temperature but the porosity of the porous LSGM scaffold decreases from 55 % at 1,100 oC to 16 % at 1,300 oC. Considering the porosity of the LSGM scaffold and connectivity and adhesion, the optimal fi...