Heather Abbott-Lyon - Activated dissociation of CO2 on Rh(111) and CO oxidation dynamics

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  Publication Details (including relevant citation   information):

  H.L. Abbott and I. Harrison, Journal of   Physical Chemistry C 111, 13137 (2007)

  Abstract:

  The activated dissociative chemisorption of CO2 on Rh(111) is   characterized theoretically with the aid of detailed balance   simulations of the CO2 product state distributions measured in   thermally driven CO oxidation experiments. A two-parameter   formulation of the physisorbed complex-microcanonical   unimolecular rate theory (PC-MURT), a local hot spot model for   the CO2 gas-surface reactivity, is used to calculate CO2   dissociative sticking coefficients, as well as the angular   yields, mean translational energies, and rovibrational energy   distributions of desorbing CO2 product from CO oxidation.   Measured CO2 product angular yields and infrared   chemiluminescence from CO oxidation are consistent with two   parallel mechanisms for activated CO2 dissociative chemisorption   on Rh(111): a direct mechanism and an indirect mechanism   involving a thermalized intermediate. The PC-MURT describes the   direct mechanism that is favored at low coverage and helps to   reveal the indirect mechanism that can be a substantial reaction   pathway (e.g., 65%) under other conditions. For the direct   mechanism, simulations of diverse experimental data indicate that   the reaction threshold energy for CO2 dissociative chemisorption   is E0 ) 73 kJ/mol, two surface oscillators participate in the   dissociative transition state, and molecular rotation is   approximately a spectator to the dissociation dynamics.   Accordingly, an experimentally consistent activation energy for   CO oxidation via Langmuir-Hinshelwood reaction kinetics is Ea'   ~99 kJ/mol.

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