Electrodeposition of Co-Mn and Cu-Mn based Spinels onto Solid Oxide Fuel Cell Interconnects

Abstract

<p>Solid oxide fuel cells are an efficient method of converting hydrocarbon fuels to electrical power. However, due to some problems with poisoning, these have made no headway in the energy market. The evaporation of chromium oxides from metallic current collectors causes rapid degradation of the cells on the cathode side. It has been shown that spinel coatings reduce the effects of chromium oxide evaporation. In this thesis, two spinel systems are explored for potential application. Cobalt-manganese spinel is a stable spinel which have a wide range of composition, while remaining sufficiently conductive. Copper-manganese spinel, which is much more conductive than cobalt-manganese, is slightly less stable, but nonetheless a candidate. All components of the spinels explored can be electrodeposited from aqueous solutions, at room temperature. By controlling the concentrations of metallic ions, and other additives, coatings can be deposited on interconnecting plates with reproducible results. The newly coated interconnects can be oxidized in-situ. For characterization, the samples for this thesis were oxidized at 800°C. Two substrate materials were used, ferritic stainless steel and a chromium-iron alloy. Stainless steel substrates showed good coating adhesion, but high concentrations of iron were found in the spinel structure. Chromium alloy substrates were better protected by spinel coatings. However, nitride formation at the substrate interface caused localized delamination of the coating. It was shown that plating operations can be scaled up to 10 cm by 10 cm plates, with little modification of the processes used.</p>