Towards understanding surface chemistry and electrochemistry of La_0.1Sr_0.9TiO_3-α based solid oxide fuel cell anodes

In the present contribution, we combine modeling and experimental study of electrochemical hydrogen oxidation at an alternative perovskite based mixed-conducting SOFC anode. Composite electrodes were produced by conventional wet ceramic processing (screen printing - spraying) and sintering on YSZ electrolytes (La_0.1Sr_0.9TiO_3-α-Ce_1-xGd_xO_2-α|YSZ) with different compositions and microstructure, and were electrochemically characterized using symmetrical button-cells configuration. An elementary kinetic model was developed and applied to explore the performance of LST based SOFC anode. A detailed multi-step heterogeneous chemical and electrochemical reaction mechanism was established taking into account transport of ions in all ionic phases, and gas transport in channel and porous media. It was found that heterogeneous chemistry at LST surface has capacitive behavior that alters the impedance spectra. In addition, surface charge-transfer reaction, which describes partial oxygen ionization, caused impedance feature and is rate-limiting at high temperature. The gas transport in the supply chamber (gas conversion) is significant only at moderate temperatures.