Xunying Wang

Semiconductor-Ionic Nanocomposite La0.1Sr0.9MnO3−δ-Ce0.8Sm0.2O2−δ Functional Layer for High Performance Low Temperature SOFC

A novel composite was synthesized by mixing La0.1Sr0.9MnO3−δ (LSM) with Ce0.8Sm0.2O2−δ (SDC) for the functional layer of low temperature solid oxide fuel cell (LT-SOFC). Though LSM, a highly electronic conducting semiconductor, was used in the functional layer, the fuel cell device could reach OCVs higher than 1.0 V without short-circuit problem. A typical diode or rectification effect was observed when an external electric force was supplied on the device under fuel cell atmosphere, which indicated the existence of a junction that prevented the device from short-circuit problem. The optimum ratio of LSM:SDC = 1:2 was found for the LT-SOFC to reach the highest power density of 742 mW·cm−2 under 550 °C The electrochemical impedance spectroscopy data highlighted that introducing LSM into SDC electrolyte layer not only decreased charge-transfer resistances from 0.66 Ω·cm2 for SDC to 0.47–0.49 Ω·cm2 for LSM-SDC composite, but also decreased the activation energy of ionic conduction from 0.55 to 0.20 eV.

Advanced Fuel Cell Based on Perovskite La–SrTiO3 Semiconductor as the Electrolyte with Superoxide-Ion Conduction

A solid oxide fuel cells performance is largely determined by the ionic-conducting electrolyte. A novel approach is presented for using the semiconductor perovskite La0.25Sr0.75TiO3 (LST) as the electrolyte by creating surface superionic conduction, and the authors show that the LST electrolyte can deliver superior power density, 908.2 mW cm-2 at just 550 °C. The prepared LST materials formed a heterostructure, including an insulating core and a superionic conducting surface layer. The rapid ion transport along the surfaces or grain boundaries was identified as the primary means of oxygen ion conduction. The fuel cell-induced phase transition was observed from the insulating LST to a super O2- conductivity of 0.221 S cm-1 at 550 °C, leading to excellent current and power outputs.