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

A detailed effects of catalystX(X = H2O, (H2O)(2), NH3, NH3 center dot center dot center dot H2O, H2O center dot center dot center dot NH3, HCOOH and H2SO4) on the HO4H -> O-3 + 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 center dot center dot center dot NH(3)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 catalystXhave been assessed. It was found fromk'(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 + O(3)reaction, thek(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 -> O-3 + H2O.