New SrMo_(1-x)Cr_xO_(3-5) perovskites as anodes in solid-oxide fuel cells

摘要

Oxides of composition SrMo_(1 x)Cr_xO_(3 δ) (x = 0.1, 0.2) have been prepared, characterized and tested as anode materials in single solid-oxide fuel cells, yielding output powers higher than 700 mW cm~2 at 850 ℃ with pure H_2 as a fuel. All the materials are suggested to present mixed ionic-electronic conductivity (MIEC) from neutron powder diffraction (NPD) experiments, complemented with transport measurements; the presence of a Mo~4'/Mo~5' mixed valence at room temperature, combined with a huge metal-like electronic conductivity, as high as 340 S cm~1 at T = 50 ℃ for x = 0.1, could make these oxides good materials for solid-oxide fuel cells. The magnitude of the electronic conductivity decreases with increasing Cr-doping content. The reversibility of the reduction-oxidation between the oxidized Sr(Mo,Cr)O_(4 δ) scheelite and the reduced Sr(Mo,Cr)O_3 perovskite phases was studied by thermogravimetric analysis, which exhibit the required cyclability for fuel cells. An adequate thermal expansion coefficient, without abrupt changes, and a chemical compatibility with electrolytes make these oxides good candidates for anodes in intermediate-temperature SOFC (IT-SOFCs).