Balance in Adsorption Energy of Reactants Steers CO Oxidation Mechanism of Ag13 and Ag12Pd1 Nanoparticles: Association Mechanism versus Carbonate-Mediated Mechanism
journal contributionposted on 25.02.2010, 00:00 by Hyun You Kim, Sang Soo Han, Ji Hoon Ryu, Hyuck Mo Lee
CO oxidation is a very useful reference reaction in catalysis by nanoparticles (NPs). Two reaction modelsan association mechanism (AM) and a carbonate-mediated mechanism (CMM)have been suggested for CO oxidation catalyzed by small NPs. It is still unclear, however, when and why these mechanisms preferentially operate. With the Ag13 crystalline NPs and the Ag12Pd1 core−shell NP, using a density functional theory calculation and a microkinetic reaction model, we found that the different reaction mechanisms can operate with different reaction intermediates accompanied by a balance in the adsorption energy of reactants. Variations in the adsorption energy of adsorbates can result from the interchange of two reaction mechanisms, even in a single NP. An AM operates when both reactants interact strongly with a NP, whereas the contribution of the CMM in CO oxidation increases when a CO molecule interacts weakly or not at all with a NP.