Sr2Fe2−xMoxO6−δ perovskite as an anode in a solid oxide fuel cell: Effect of the substitution ratio

•The Mo content in Sr2Fe2−xMoxO6 anode influences the performance of the fuel cell.•The electrical conductivity is not the limiting factor in the anode reaction steps.•The activity of the SFMO anode is influenced by the surface Fe2+/Fe3+ redox couple.

Double perovskite, Sr2Fe2−xMoxO6−δ (SFMO), as an anode material of the solid oxide fuel cell (SOFC) exhibits excellent performance. The effects of the substitution ratio of Mo on its properties and electro-catalytic activity are examined. The SFMO anode shows a porous structure with a pore size of several micrometers. Using hydrogen and dry methanol as the fuels, the single cell with the SFMO anode with x between 0.4 and 0.6 gives the maximum power outputs of 541 and 387 mW cm−2 at 1073 K, respectively. The electro-catalytic activity of SFMO anodes exhibits an order of Sr2Fe1.4Mo0.6O6−δ > Sr2Fe1.5Mo0.5O6−δ > Sr2Fe1.6Mo0.4O6−δ. However, the overall conductivity of SFMO displays a reverse order. With the increase of the Mo content, the surface Fe2+/Fe3+ ratio increases regularly, but the Mo5+/Mo6+ radio shows a peak in Sr2Fe1.5Mo0.5O6−δ. It is concluded that the electro-activity of the SFMO anodes for the electro-oxidation of hydrogen and methanol is not limited by their conductivity, but their surface Fe2+/Fe3+ redox couple.

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