Combined effect between PVP and glass wool for improvement of the photocatalytic activity under visible light of bismuth (III) oxyhalide and access to a-Bi2O3-BiOI-BiOBr

Improvement of the photocatalytic efficiency of BiOI/BiOBr composite have been obtained by a combined effect between a structuring agent like polyvinylpyrrolidone (PVP) and glass wool (GW) introduced during their synthesis by solvothermal (STP) or hydrothermal (HTP) process. The photocatalysts were characterized by XRD, SEM, XPS, UV-Visible DRS, BET and EDX and their activity tested in the photo-degradation of Rhodamine B (RhB) under visible light. Photocatalyst prepared by STP have higher photocatalytic efficiency than those prepared by HTP, moreover, the presence of PVP and GW greatly improve this efficiency, a total discoloration of RhB solution (20 mg L-1) being obtained after 18 min. The photodegradation mechanism has been proposed by the identification of the radical species responsible for the degradation. Indeed, two radical species have been identified for the catalyst prepared without GW, most of them the hole (h(+)) and moderately super oxide anion (O-2(center dot-)). Differently, for the catalyst prepared with GW, three species have been identified, h(+) being the main species with a moderate contribution of the hydroxyl radical (HO center dot) and O-2(center dot-).