Stability study of possible air electrode materials for proton conducting electrochemical cells

In the search for new air electrode materials for Proton Conducting Cells (PCC), the case of basic (rare earth and/or alkaline earth containing) oxocobaltites has been considered to find materials exhibiting mixed electron and proton conductivity. The stability in dry and wet air of classical (cubic and derived) as well as hexagonal 2H perovskite structures has been examined. The following compositions were studied: LaCoO3, Sr0.5La0.5CoO3, SrCoO3, Ba0.5Sr0.5CoO3, BaCoO3 and Ba0.5La0.5CoO3. Among them, four materials appeared to be stable enough in the selected operating conditions of ageing: BaCoO3, LaCoO3, Sr0.5La0.5CoO3 and Ba0.5La0.5CoO3. The reactivity study of the latter materials with the classical BaZr0.9Y0.1O3 electrolyte material has also been studied. Oxygen vacancy formation and structural water incorporation was analyzed by iodometry and TGA allows identifying them as the best compromise of the series for a PCC air electrode application.