Efficient and stable oxidative steam reforming of ethanol for hydrogen production: Effect of in situ dispersion of Ir over Ir/La2O3

La2O3-supported Ir catalyst was prepared by wetness impregnation method for the oxidative steam reforming of ethanol (OSRE). Fresh, reduced, and used catalysts were characterized by N2 adsorption, H2 chemisorption, XRD, FT-IR, TEM, and XPS. La2O3 would transform into hexagonal La2O2CO3 during OSRE, which suppress coking effectively. Reduced Ir metal can interplay with La2O2CO3 to form Ir-doped La2O2CO3. It dynamically forms and decomposes to release active Ir nanoparticles, thereby preventing the catalyst from sintering and affording high dispersion of Ir/La2O3 catalysts at elevated temperatures. By introducing ultrasonic-assisted impregnation method during the preparation of a catalyst, the surface Ir concentration was significantly improved, while the in situ dispersion effect inhibited Ir from sintering. The Ir/La2O3 catalyst prepared by the ultrasonic-assisted impregnation method is highly active and stable for the OSRE reaction, in which the Ir crystallite size was maintained at 3.2 nm after 100 h on stream at 650 °C and metal loading was high up to 9 wt%.