Co3O4 nanostructures and Co3O4 supported on halloysite nanotubes: New highly active and thermally stable feasible catalysts for CO oxidation

Co3O4 nanostructures were successfully pre-synthesized and then, deposited on natural halloysite nanotubes (HNTs) surfaces. A typical porous Co3O4 network was initially obtained, consisting of tightly assembled and sintered nanocrystallites. Nevertheless, when halloysite was included, Co3O4 nanoparticles, with a narrow size distribution (4.6 +/- 1.2 nm), were uniformly attached on the HNTs surface. Bare Co3O4 nanostructure and Co3O4-HNTs nanocomposite (10% w/w Co3O4), presented high catalytic activity in CO oxidation. Regarding the catalytic behavior, bare Co3O4 nanostructures reached complete conversions from 130 to 900 degrees C, while Co3O4-HNTs nanocomposite produced a CO oxidation efficiency of 97% between 350 and 900 degrees C. Besides, a cyclability analysis was achieved at 150 and 500 degrees C. None of the samples presented an important decrease in the catalytic activity, as the CO conversion efficiencies were maintained during all the cycles performed. Finally, a first approximation of catalyst stability in the presence of H2S was studied.