Shape and size controlled α-Fe2O3 nanoparticles as supports for gold-catalysts: Synthesis and influence of support shape and size on catalytic performance

Synthesis of shape- and size- controlled alpha-Fe2O3 nanoparticles was performed through a hydrothermal method assisted with amino acids. The products were characterized by transmission electron microscopy and X-ray diffraction. It was found that the type of amino acids has significant impact on the shape and size of the obtained alpha-Fe2O3 nanoparticles. The use of acidic amino acids typically leads to the formation of alpha-Fe2O3 nanoparticles with spindle shape. However, rhombohedrally shaped alpha-Fe2O3 nanoparticles were formed in the case of basic amino acids. When gold colloidal nanoparticles were deposited on the surfaces of alpha-Fe2O3 nanoparticles, Au/alpha-Fe2O3 catalysts display substantial differences in catalytic activities in CO oxidation for the differently shaped alpha-Fe2O3 nanoparticles used as supports. In general, spindle shaped Au/alpha-Fe2O3 shows higher catalytic activity than catalysts based on rhombohedral iron oxide. Under our catalytic test conditions, for spindle shaped Au/alpha-Fe2O3 catalyst, large hematite crystals induce higher catalytic activity than smaller ones, whereas for rhombohedral Au/alpha-Fe2O3 catalysts, medium-sized alpha-Fe2O3 nanocrystals show high catalytic activity for CO oxidation. (C) 2009 Elsevier B.V. All rights reserved.