Direct Evaluation of Oxygen Chemical Potential Distribution in an SOFC Cathode by In Situ X-Ray Absorption Spectroscopy

Abstract

Oxygen chemical potential distribution in a porous La0.6Sr0.4CoO3-δ (LSC64) electrode on a Ce0.9Gd0.1CoO1.95- δ (GDC) electrolyte under polarization was evaluated by using in situ X-ray absorption spectroscopy (XAS) at P(O2) = 10-2 bar and 873 K. The application of synchrotron X-ray focused into the submicrometer size enabled us to experimentally clarify the oxygen potential distribution in the vicinity of electrode/electrolyte interface with the position resolution of micrometer. Electrochemical impedance spectroscopy (EIS) measurements, followed by the analysis assuming the transmission line model (TLM) as an equivalent circuit, were performed with the same electrochemical cell for the XAS measurements. Based on the results by in-situ micro XAS and EIS measurements, the effective reaction area in the porous LSC64 electrode was discussed.

(Invited) Triple Phase Boundary Reaction in a Mixed-Conducting SOFC Cathode

“…In our previous work [3,4], the reaction distribution in a porous La 0.6 Sr 0.4 CoO 3-δ cathode was investigated by means of operando micro X-ray absorption spectroscopy (operando µ-XAS). As results, it was found the electrode reaction took place within the area less than a few micrometers from the electrode/electrolyte interface under 10 -2 bar of oxygen partial pressure p(O 2 ) at 873 K, suggesting that the area where the electrode reaction progresses is very limited.…”

Operando Soft X‐ray Absorption Spectroscopic Study on a Solid Oxide Fuel Cell Cathode during Electrochemical Oxygen Reduction

“…[16][17][18] The electronic and local structural changes of MIEC electrodes were analyzed from the 3d transition-metal K-edge in these studies. [16][17][18] The electronic and local structural changes of MIEC electrodes were analyzed from the 3d transition-metal K-edge in these studies.…”

“…Hard X-ray radiation is useful for operando observation because of its high permeability.For instance, the electrochemical reactiona tt he fuel cell electrode was studied by hard X-ray absorption spectroscopy. [16][17][18] The electronic and local structural changes of MIEC electrodes were analyzed from the 3d transition-metal K-edge in these studies. However,t he 3d transition-metal K-edge does not directly represent the electronic structure of the outermost orbitalo ft he electrode material, since the X-ray absorption spectra at the 3d transition-metal Kedge mainly observes the excitation of ac ore electron from the 1s to 4p orbital.…”

Reduction Behavior of Ni in a Ni/YSZ Anode Revealed byOperandoFluorescence X-ray Absorption Spectroscopy

“…Basic knowledge about redox behavior and oxidation state of Ni under an operating condition is essential to rationally design a new class of anode materials for SOFC. Operando X-ray absorption spectroscopy (XAS) is a powerful method of choice to investigate the relationship between the oxidation state of an active site and cell performance at work (13)(14)(15)(16)(17).…”