Two-step synthesis of Fe2O3 and Co3O4 nanoparticles: towards a general method for synthesizing nanocrystalline metal oxides with high surface area and thermal stability

A simple, two-step method using activated carbon (AC) as a support/ scaffold was developed to synthesize metal oxide nanocrystalline materials (NCMs). In the first step, metal nitrate precursors were deposited by wet impregnation onto the AC, then heated in argon at 350 degrees C to immobilize the metal oxides. In the second step, the AC was removed by calcination in air at 500 degrees C, to obtain the unsupported metal oxide NCMs. Characterization by N-2-sorption isotherms, TGA, XPS and EXAFS reveals that the metal oxide particles are crystalline and nanometre-sized, with surface areas up to 148 m(2) g(-1). Moreover, the TEM images show particle sizes in the range 5-10 nm, even after calcination at 500 degrees C for 2 h. Their thermal stability and high surface areas, together with the nanometre-sized structures, make them promising materials for catalytic applications (e. g., CO oxidation).