The HO4H → O3 + H2O reaction catalysed by acidic, neutral and basic catalysts in the troposphere

Abstract

A detailed effects of catalyst X (X = H2O, (H2O)2, NH3, NH3···H2O, H2O···NH3, HCOOH and H2SO4) on the HO4H → O3 + H2O reaction have been investigated by using quantum chemical calculations and canonical vibrational transition state theory with small curvature tunnelling. The calculated results show that (H2O)2-catalysed reactions much faster than H2O-catalysed one because of the former bimolecular rate constant larger by 2.6–25.9 times than that of the latter one. In addition, the basic H2O···NH3 catalyst was found to be a better than the neutral catalyst of (H2O)2. However it is marginally less efficient than the acidic catalysts of HCOOH, and H2SO4. The effective rate constant (k't) in the presence of catalyst X have been assessed. It was found from k't that H2O (at 100% RH) completely dominates over all other catalysts within the temperature range of 280–320 K at 0 km altitude. However, compared with the rate constant of HO4H → H2O + O3 reaction, the k eff values for H2O catalysed reaction are smaller by 1–2 orders of magnitude, indicating that the catalytic effect of H2O makes a negligible contribution to the gas phase reaction of HO4H → O3 + H2O. Highlights A detailed effects of catalyst of H2O, (H2O)2, NH3, NH3···H2O, H2O···NH3, HCOOH and H2SO4 on the HO4H → O3 + H2O reaction has been performed. From energetic viewpoint, H2SO4 exerts the strongest catalytic role in HO4H → O3 + H2O reaction as compared with the other catalysts. At 0 km altitude H2O (at 100% RH) completely dominates over all other catalysts within the temperature range of 280–320 K. HO4H → H2O + O3 reaction with H2O cannot be compete with the reaction without catalyst, due to the fact that the effective rate constants in the presence of H2O are smaller.