Abstract

Suspensions of cobalt spinel (Co3O4) powders (median size 6 µm and 0.3 µm) were r.f. plasma sprayed to form electrocatalytically active anode layers for alkaline water electrolysis. Stable cobalt oxide suspensions of low viscosity and exceeding 50wt.% solid phase content have been processed. A spheroidization study revealed the formation of large spherical powder particles (- 30 + 80 µm). Cobalt oxide coatings were produced by this novel r.f.-Suspension Plasma Spraying (SPS) method. The porosity was controlled by optimizing the spray distance and the reactor pressure. The main disadvantage of the thermal plasma processing of cobalt spinel, i.e. the decomposition of the spinel phase into CoO, could not be prevented, not even with the application of an 80% oxygen plasma. With a relatively low power oxygen plasma post-treatment the deposited CoO layers can be oxidized to Co3O4 resulting in a promising improvement of the electrochemical performance of the anode layers.

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