On the methane oxidation activity of Sr_2(MgMo)_2O_(6-δ): a potential anode material for direct hydrocarbon solid oxide fuel cells

摘要

Sr_2(MgMo)_2O_(6-δ) and materials of nominal compositions with increased and decreased Mo content were synthesized and their stability and catalytic activity towards CH_4 oxidation characterized under solid oxide fuel cell (SOFC) anode conditions. Sr_2(MgMo)_2O_(6-δ) was synthesized as a double perovskite. Materials with increased Mo content formed a mixture of the double perovskite Sr_2MgMoO_(6-δ) and the single perovskite SrMoO_3, after synthesis in H_2, with the amount of SrMoO_3 increasing with increasing Mo content. SrMoO_3 is unstable in air and slowly oxidized to the scheelite-structured impurity SrMoO_4. All compositions decomposed to Mo, MgO and SrO in dry 20% CH_4/N_2 at temperatures ≥ 850 ℃. CH_4 reaction rates were catalytically limited with measured rates significantly lower than for La_(0.75)Sr_(0.25)Cr_(0.5)Mn_(0.5)O_(3-δ). Rates increased by 1-2 orders of magnitude when 2 wt-% of Pt was added to the surface.