Kinetic study of the reaction H 2O 2+H→H 2O+OH by ab initio and density functional theory calculations

Abstract

Theoretical investigations on the kinetics of the elementary reaction H 2O 2+H→H 2O+OH were performed using the transition state theory (TST). Ab initio (MP2//CASSCF) and density functional theory (B3LYP) methods were used with large basis set to predict the kinetic parameters; the classical barrier height and the pre-exponential factor. The ZPE and BSSE corrected value of the classical barrier height was predicted to be 4.1 kcal mol −1 for MP2//CASSCF and 4.3 kcal mol −1 for B3LYP calculations. The experimental value fitted from Arrhenius expressions ranges from 3.6 to 3.9 kcal mol −1. Thermal rate constants of the title reaction, based on the ab initio and DFT calculations, was evaluated for temperature ranging from 200 to 2500 K assuming a direct reaction mechanism. The modeled ab initio-TST and DFT–TST rate constants calculated without tunneling were found to be in reasonable agreement with the observed ones indicating that the contribution of the tunneling effect to the reaction was predicted to be unimportant at ambient temperature.