Mapping electrochemically driven gas exchange of mixed conducting SrTi _0.7Fe _0.3O _3 − δ and Ce _0.8Gd _0.2O _1.9 thin films by ¹⁸O tracer incorporation under reducing atmosphere

Abstract

Thermally and electrochemically driven ¹⁸O tracer exchange experiments in H ₂/H ₂ ¹⁸O atmosphere were performed on SrTi _0.7Fe _0.3O _3 − δ and Ce _0.8Gd _0.2O _2 − δ thin films on single crystalline YSZ substrates. Noble metal current collectors were deposited on both films and electrochemically polarized during the exchange experiment. The resulting tracer distribution was analyzed by spatially resolved secondary ion mass spectrometry. Increased tracer fraction near the current collectors was found under cathodic polarization and decreased tracer fraction under anodic polarization. High cathodic bias leads to enhanced n-type electronic conductivity, which increases the extent of the electrochemically active zone.

Highlights

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  ¹⁸O from tracer marked water was incorporated in SrTi _0.7Fe _0.3O _3–δ and Ce _0.8Gd _0.2O _1.8 thin films.

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  On both MIEC thin films, Pt and Au current collectors were applied beneath the film and ontop, respectively.

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  Cathodic polarization extended the oxygen incorporation zone from the current collector along the free electrode surface.