A new technique for in-situ Raman spectroscopic analysis of redox mechanisms at the solid oxide fuel cell electrodes
Solid oxide fuel cell (SOFC) is a high-effective electrochemical device which directly convert chemical energy of fuel and oxidizer in electrical and thermal energy. Effectiveness of SOFC is strongly dependent on the kinetics of the electrode redox reactions which take place at the “electrode | electrolyte” interface. Traditional electrochemical techniques of reaction studies are impedance spectroscopy and current-voltage measurements. Current-voltage method is cumulative, and doesn’t give enough information about chemical reactions in SOFC electrodes.
Impedance spectroscopy uses simplified processes’ models for interpretation of the unclear and doubtful results obtained. One of possible techniques without these drawbacks is Raman spectroscopy. The Raman spectroscopy is widely used to investigate both cathodic and anodic processes in SOFC. Previous Raman spectroscopy studies of SOFC obtained results from and mainly related to outer boundaries of the model electrochemical cells, primary electrode surface. The most interesting point of the electrode system is “electrode | electrolyte” interface, where the electrochemical reaction take place, it cannot be accessed looking at surface and edge areas. This is because the laser excitation radiation has low penetration depth (near 1 um). To avoid that problem in the present work optically transparent, single-crystal, scandia-yttria stabilized zirconia oxide membrane was used. Electrodes of special geometry make possible to directly observe Raman spectra from the TPB zone.
A new technique described in that article also uses a traditional impedance spectroscopy and current-voltage methods. This combination of experimental techniques gives opportunity to study local electrochemical reactions exactly in SOFC working conditions: working temperature, separated gas chambers and current load. Present work is focused on the results of in-situ investigation of redox reactions in anode electrode with usage of the new technique.