A novel strategy for low-temperature synthesis of Ruddlesden-Popper type layered perovskite La3Mn2O7+δ for methane combustion

In comparison to the conventional high-temperature (>= 1300 degrees C) preparation methods, a novel strategy for the synthesis of a Ruddlesden-Popper (R-P) type layered perovskite La3Mn2O7+delta (LLM) at a relatively low temperature (700 degrees C) was proposed. The conventional perovskite LaMnO3 (LM) and the nominal La3Mn2O7+delta (NLM) synthesized by the citric acid sol-gel method were compared. Density functional theory calculations were performed to expound the synthesis strategy. The results of X-ray diffraction and high-resolution transmission electron microscopy demonstrated the formation of an R-P type layered perovskite crystal structure in the LLM samples. The results of X-ray photoelectron spectroscopy and hydrogen-temperature-programmed reduction showed that the LLM sample calcined at 700 degrees C possessed richer and more stable active lattice oxygen species than the other samples because of its two-dimensionally ordered loose intercalated structure. Thus, the LLM samples exhibited excellent thermal stability and higher activity for methane combustion than the LM and NLM samples. After calcination at 1000 degrees C, the LLM samples still had a relatively higher specific surface area (15.28 m(2) g(-1)) than the LM samples (6.64 m(2) g(-1)).