Spontaneous Deprotonation of HO2 • at Air-Water Interface

HO2 center dot is a crucial radical in atmospheric chemistry, with applications ranging from HO2 center dot/OH center dot interconversion to controlling the budget of various trace gases in the atmosphere. It is known that one of the potential sinks for HO2 center dot is clouds and aerosols, though the mechanism is not clear to date. In the present study, using Born-Oppenheimer molecular dynamics simulations, we have demonstrated that the dissociation of HO2 center dot on the surface of a water droplet, as well as in the bulk phase, is a spontaneous process. In addition, we have computed the Gibbs free energy for the deprotonation of HO2 center dot on both the surface and in the bulk, which suggests that deprotonation of HO2 center dot on the surface occurs faster compared to the same in the bulk.