Characterization of La1-xSrxMnO3 perovskite catalysts for hydrogen peroxide reduction.
We investigated the crystalline phase and electronic structure of perovskite-type La1-xSrxMnO3 (0.0 ≤ x ≤ 1.0) (LSMx) catalysts synthesized via the citric sol-gel route, for H2O2 reduction. The resulting materials were characterized by XRD, XANES, TR-XANES, and TPO and, after calcination, consisted of cubic perovskite for 0.0 ≤ x ≤ 0.8 and hexagonal perovskite for x = 1.0. Mn species in the precalcined catalysts were oxidized to Mn(3+) for x = 0.0 to 0.6 and to Mn(2+) for x = 0.8 and 1.0. After calcination, Mn species were present in a mixed oxidation state of Mn(3+)/Mn(4+), while Sr(2+) and La(3+) were not altered. TR-XANES and TPO showed that Mn species were oxidized at 210-220 °C and formed active perovskites LSM0.4 and LSM0.0 at 580 °C and 640 °C. This shows that Sr doping can reduce the oxidation temperature of LSMx with 0.2 ≤ x ≤ 0.4. However, the concentration of Mn(4+) in LSMx is increased which is useful for enhancing their catalytic activity and stability. When tested in an alkaline electrolyte, LSM0.6 containing the optimum Mn(4+)/Mn(3+) ratio promoted the formation of hydroxyl via the oxygen intercalation reaction and exhibited low polarization resistance and the highest catalytic activity for H2O2 reduction.
Department of Materials Science, Kasetsart University, Bangkok, 10900 Thailand.
C
C
Yunphuttha
Photonics Technology Laboratory, National Electronics and Computer Technology Center, Patumthani, 12120 Thailand.
S
S
Porntheeraphat
Department of Chemistry, Kasetsart University, Bangkok, 10900 Thailand.
A
A
Wongchaisuwat
Department of Chemistry, Kasetsart University, Bangkok, 10900 Thailand.
S
S
Tangbunsuk
Chemical and Biological Engineering Department, Colorado School of Mines, Golden, Colorado 80401, USA.
D W M
DW
Marr
Department of Chemistry, Kasetsart University, Bangkok, 10900 Thailand and Center of Advanced Studies in Tropical Natural Resources, National Research University, Kasetsart University, Bangkok, 10900 Thailand. fscipdv@ku.ac.th.
P
P
Viravathana