Potential Energy Surfaces for the Reactions of HO2 Radical with CH2O and HO2 in CO2 Environment

We report on potential energies for the transition state, reactant, and product complexes along the reaction pathways for hydrogen transfer reactions to hydroperoxyl radical from formaldehyde H 2 CO + HO 2 → HCO + H 2 O 2 and another hydroperoxyl radical 2HO 2 → H 2 O 2 + O 2 in the presence of one carbon dioxide molecule. Both covalently bonded intermediates and weak intermolecular complexes are identified and characterized. We found that reactions that involve covalent intermediates have substantially higher activation barriers and are not likely to play a role in hydrogen transfer kinetics. The van der Waals complexation with carbon dioxide does not affect hydrogen transfer from formaldehyde, but it lowers the barrier for hydroperoxyl self-reaction by nearly 3 kcal/mol. This indicates that CO 2 environment is likely to have catalytic effect on HO 2 self-reaction, which needs to be included in kinetic combustion mechanisms in supercritical CO 2 .