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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