Hydrothermally fabricated single-crystalline strontium-substituted lanthanum manganite microcubes for the catalytic combustion of toluene

La1−xSrxMnO3−δ (x = 0.4, 0.5, and 0.6) catalysts were fabricated hydrothermally from KMnO4, MnCl2 (KMnO4/MnCl2 molar ratio = 3/7), and stoichiometric amounts of lanthanum and strontium nitrates in KOH solution. The physicochemical properties of the materials were characterized by a number of analytical techniques. It was found that the La1−xSrxMnO3−δ samples fabricated at 250 °C are single-crystalline perovskite-type oxides in the form of microcubes. The as-fabricated La1−xSrxMnO3−δ materials display various states of oxygen nonstoichiometry. The total amount of oxygen vacancies and Mn4+ in the catalysts decreases in the order of La0.5Sr0.5MnO3−δ > La0.4Sr0.6MnO3−δ > La0.6Sr0.4MnO3−δ. It has been found that the trends of catalyst reducibility and catalytic performance of the three catalysts follow a similar order. We observed 100% toluene conversion at 255 °C over the La0.5Sr0.5MnO3−δ catalyst, 113 °C lower than that observed over a polycrystalline La0.5Sr0.5MnO3−δ catalyst prepared by calcination at 950 °C. The excellent performance of the former can be related to the high Mn4+/Mn3+ ratio, distinct oxygen nonstoichiometry, and single-crystalline structure of the catalyst.

Single-crystalline perovskite-type oxide La1−xSrxMnO3−δ microcubes are fabricated via a hydrothermal route. 100% toluene conversion is achieved over the La0.5Sr0.5MnO3−δ catalyst at 255 °C, which is 113 °C lower than that over the polycrystalline La0.5Sr0.5MnO3−δ catalyst. The excellent performance is related to the high Mn4+/Mn3+ ratio, distinct oxygen nonstoichiometry, and single-crystalline structure. Figure optionsDownload as PowerPoint slide