Effect of the A-site cation on methane oxidation of perovskite-type (La1−xMx)CoO3 (M=Ca, Sr, and Ba)

Perovskite-type (La1−xMx)CoO3 (M=Ca, Sr, and Ba) synthesized at 700 °C in air using the polymerizable complex method had a rhombohedral perovskite-type structure in the range of x≤0.06. The oxygen content of the samples was 2.98–2.99, and the specific surface area was 3.5–8.3 m2/g regardless of the M ion or x. The Rietveld method indicated that the Co–O distance was also constant regardless of the M ion or x, and that the Co–O–Co angle between two CoO6 octahedra increased with an increase in the ionic radius of the M ion. The temperature corresponding to the 50% conversion (T1/2) of CH4 oxidation was almost constant for the samples with x=0.04, while the T1/2 of the samples with x=0.06 was linearly lowered with increases in the ionic radius of the M ion.