(144e) Size Effect of Cobalt-Oxide Nanoparticles for CO Oxidation: An Experimental and Computational Study

CO oxidation is important in air purification, lowering the toxicity of automobile exhausts, during selective oxidation of the feed stream to a fuel cell, and for several other potential applications. Noble metals are highly active catalysts that are moisture tolerant and stable against deactivation.  However, the popularity of these catalysts is affected by their higher cost and limited availability. Recently, CO oxidation using cobalt has been the subject of attention due to the lower cost of cobalt compared to the noble metal counterparts. A systematic understanding of the catalytic activity of cobalt-oxide nanoparticles, especially the role of the nanoparticle size, has yet to be established. Here, we use a temperature programmed method with an in-situ FTIR spectroscopic characterization to systematically study nanoparticle size effect on catalytic CO oxidation. For a well-defined and model catalyst, stable cobalt-oxide nanoparticles of sizes 1 to 14nm were synthesized and immobilized on surface modified SiO₂ colloidal supports. In-situ FTIR experimental data was interpreted using kinetic modeling to measure dependence of nanoparticle size on activation energies for CO oxidation reaction mechanism. The proposed reaction energetics were supported by DFT calculations on a CoO(100) surface.