Abstract
NiO and CeO2 were prepared via flame spray pyrolysis. The specific surface area and total pore volume were 251 m2 g–1 and 2.3 cm3 g–1 for NiO and 338 m2 g–1 and 3.3 cm3 g–1 for CeO2, respectively. The high porosity and surface area of the NiO allowed deposition of small CeO2 particles (∼5 nm) by the impregnation of cerium acetate monohydrate. The particles were reduced using 5 % H2 at 500 °C for 1 h which converted NiO to metallic Ni. During the reduction, the growth of Ni particles was hindered by CeO2 particles. Consequently, the Ni size was relatively small (∼20 nm) despite the extremely high Ni content (80 wt%), as observed by scanning transmission electron microscopy. In contrast, incorporation of Ni using nickel acetate tetrahydrate into the CeO2 support resulted in formation of inhomogeneous Ni particles (20-100 nm) after H2 reduction. H2 chemisorption measurement showed the surface area of Ni particles in the former catalyst was 13.7 m2 g–1, which was 2.4 times larger than that in the latter catalyst. The former catalyst exhibited remarkable performance for CO2 methanation (47 % CO2 conversion at 250 °C), 2 times higher than in the latter catalyst.
