Fig. 4.

ESR spectra for superoxide radical (^·O^–₂/HOO^·) adducts with DMPO during photodegradation of Rhodamine B (RhB) (A), the concentration profiles for the formation of H₂O₂ during the degradation of RhB (10 μM) (B), the proposed mechanism of the degradation of RhB under visible-light irradiation (C), and example VB and CB positions for TiO₂ and Bi₂WO₆ and the potential of the radicals’ redox couples ^·OH/H₂O and O₂/^·O₂⁻. In ESR spectra, (a) shows 0.6 V versus saturated calomel electrode (SCE) under visible irradiation; (a1) −0.6 V versus SCE in the dark; (b) −0.6 V versus SCE under visible irradiation. In H₂O₂ concentration profiles, (a) shows profile of 0.6 V versus SCE under visible irradiation; (a2) with only electrolysis at a bias of −0.6 V versus SCE; (b) under visible light and at a bias of −0.6 V versus SCE [22]

Reproduced with permission from the American Chemical Society