Operando Evaluation of the Electrochemically Active Area in a Solid Oxide Fuel Cell Porous Electrode by Micro X-ray Absorption Spectroscopy
Yoshinobu Fujimaki, Takashi Nakamura, Yuta Kimura, Kiyofumi Nitta, Oki Sekizawa, Yasuko Terada, Keiji Yashiro, Tatsuya Kawada, Koji Amezawa
Abstract
High Resolution Image Download MS PowerPoint Slide An operando X-ray absorption spectroscopic technique, which enables us to measure X-ray absorption spectra with a position resolution of submicrometers at increased temperatures while controlling atmospheres and passing an electrical current through the specimen, was developed. By applying this technique, the electrochemically active area in a porous La 0.6 Sr 0.4 CoO 3−δ electrode for a solid oxide fuel cell (SOFC) was experimentally and directly evaluated for the first time. The characteristic length of the active area was approximately 1 μm from the electrode–electrolyte interface under a cathodic overpotential of 140 mV at 873 K under 10 –2 bar of P (O 2 ), although the investigated electrode was thicker than 50 μm. This demonstrated that a reaction in an SOFC electrode inhomogeneously proceeds in a very limited area near the electrode–electrolyte interface, even when a mixed ionic and electronic conducting oxide is used as the electrode, and that direct evaluation of the active area can provide guidelines for high-performance electrode design.