Hydrothermal synthesis and catalytic performance of single-crystalline La2−xSrxCuO4 for methane oxidation

The microsized perovskite-like oxide La2−xSrxCuO4 (x = 0, 1) single crystallites with a rod-like morphology were fabricated with KOH as the alkaline source at a hydrothermal temperature of 180–260 °C and after calcination at 850 °C, and characterized by means of the XRD, BET, SEM, SAED (selected area electron diffraction), O2-TPD, and H2-TPR techniques. The catalytic performance of the materials was evaluated for methane combustion. It is shown that (i) the single-crystalline cuprate catalyst outperformed its polycrystalline counterpart; (ii) the doping of Sr2+ to the La2CuO4 lattice enhanced the catalytic activity; (iii) the LaSrCuO4 catalyst fabricated with 12 mol/L KOH as the alkaline source at a hydrothermal temperature of 260 °C showed the best performance (the temperature for 90% CH4 conversion = 667 °C) for methane combustion at CH4/O2 molar ratio = 1/10 and SV = 50,000 mL/(g h); and (iv) there was a clear relationship between the α-oxygen desorption or reducibility and catalytic activity. It is concluded that the more adsorbed oxygen species, better reducibility, single crystallinity, and unique morphology are responsible for the excellent performance of the LaSrCuO4 single crystallite in catalyzing the combustion of methane.