Bismuth oxyhalide as efficient photocatalyst for water, air treatment and bacteria inactivation under UV and visible light

Fifteen bismuth oxyhalides were synthetized, including BiOX, BiOX/BixOyXz, heterostructures and BiOXxY1-x (X, Y = Cl, Br, I) solid solutions. The photocatalytic activity and intermediates formation of as-prepared bismuthbased semiconductors (BBS) were compared with the benchmark TiO2 P25 photocatalyst for NOx air purification, phenol decomposition, and E.Coli bacteria inactivation. TiO2 P25 possessed the highest photocatalytic oxidation rate of phenol (K = 0.003 min-1) and NO degradation efficiency (eta = 38 %) when exposed to UV light, but also the lowest performance under visible light on both photocatalytic process (K = 0.0007 min-1 and eta = 14 %). Under visible light, BiOI/Bi4O5I2 or solid solutions (BiOI0.5Cl0.5 and BiOI0.5Br0.5) enhanced the photocatalyic for phenol degradation (K = 0.01-0.026 min-1) and NO (35-37 %). BBS samples generated more NO2 during NOx oxidation, but less typical intermediates (benzoquinone, hydroquinone and catechol) during phenol decomposition were detected. BiOCl0.5I0.5 and BiOBr0.5I0.5 composites exhibited the most outstanding antibacterial performance under both irradiation conditions resulting in E. coli 102-3 cfu/mL after 60 min irradiation. The differences can be mainly linked to a different ROS-mediated mechanism of TiO2 and BBS. The BBS photocatalytic results is closely related to the balance between effective light absorption and adequate redox potentials.