EPR study of electron trapping on partially hydroxylated alkali-earth oxides occurring during SO2 disproportionation.

We used the Electron Paramagnetic Resonance (EPR) technique to study the interaction of SO2 molecules on bare and partially hydroxylated Alkali-Earth Oxides surface (AEOs). When SO2 is adsorbed on the surfaces of higher basicity (CaO and SrO) disproportionation reaction occurs with formation of SO2•- radical. We show also that, when the same reaction is present on partially hydroxylated surfaces a fraction of the electrons exchanged during the redox process are trapped on the oxides surface forming colour centres ((H+)(e-) centres).