Photogeneration of hydrogen peroxide in aqueous TiO 2 dispersions

Abstract

Evidence is presented which demonstrates that titanium dioxide does in fact photogenerate H 2 O 2 in the presence of the donor sodium formate. However, this H 2 O 2 has only a transient existence in aqueous dispersions. This was confirmed by experiments in which H 2 O 2 was injected into the dispersion. The reasons for the lability of H 2 O 2 are discussed and possible mechanisms presented. Electron paramagnetic resonance experiments using spin traps reveal that photolysis of TiO 2 dispersion generates •OH radicals in the donor-free case while •CO 2 radicals are observed in the presence of formate. These results are also consistent with H 2 O 2 generation.