Liquid-Gas Interface of Iron Aqueous Solutions and Fenton Reagents

Fenton chemistry, involving the reaction between Fe²⁺and hydrogen peroxide, is well-known due to its applications in the mineralization of extremely stable molecules. Different mechanisms, influenced by the reaction conditions and the solvation sphere of iron ions, influence the fate of such reactions. Despite the huge amount of effort spent investigating such processes, a complete understanding is still lacking. This work combines photoelectron spectroscopy and theoretical calculations to investigate the solvation and reactivity of Fe²⁺and Fe³⁺ions in aqueous solutions. The reaction with hydrogen peroxide, both in homogeneous Fenton reagents and at the liquid-vapor interface, illustrates that both ions are homogeneously distributed in solutions and exhibit an asymmetric octahedral coordination to water in the case of Fe²⁺. No indications of differences in the reaction mechanism between the liquid-vapor interface and the bulk of the solutions have been found, suggesting that Fe³⁺and hydroxyl radicals are the only intermediates.