Experimental Confirmation of HO Adsorption at the Water-Air Interface.

Recent work has reported that hydrogen peroxide is formed at the air-water interface. Given the reduced solvation environment there, this process could give rise to enhanced production of OH from HO photolysis at the interface. These considerations give some importance to understanding the adsorption thermochemistry of hydrogen peroxide. Although there are two molecular dynamics studies that provide the adsorption free energy, to date there is no experimental verification that HO adsorbs at the air-water interface. Here we use glancing-angle Raman spectroscopy to follow the surface adsorption behavior of this molecule. Using standard states of 1 mol L for each of the bulk and surface phases yields a Δ° of -5 kJ mol at 293 K, comparable to that obtained for DMSO.