Facet-Heterojunction-Based Z-Scheme BiVO4{010} Microplates Decorated with AgBr-Ag Nanoparticles for the Photocatalytic Inactivation of Bacteria and the Decomposition of Organic Contaminants

In the past few years, BiVO4 has received much research attention as one of the most promising photocatalysts to deal with pathogenic bacteria and organic pollutants in wastewater. However, low photocatalytic efficiency is still the main obstacle to its practical applications. Herein, we first fabricated a facet-heterojunction-based Z-scheme photocatalyst AgBr-Ag-BiVO4{010} (BiVO4{010} microplates decorated with AgBr-Ag nanoparticles) to boost the photocatalytic activity of BiVO4 for bacterium inactivation and organic pollution treatment. On account of the directed migration of photogenerated electrons in BiVO4, Ag nanoparticles were selectively produced on the {010} facets of BiVO4 microplates during photoreduction, and the out layer of Ag nanoparticles was subsequently transformed into AgBr via the co-operation of Fe3+ and Br-. The photocatalytic Escherichia coli K-12 inactivation results indicated that AgBr-Ag-BiVO4{010} displays optimal photocatalytic activity for bacterium inactivation among the current BiVO4-based photocatalytic materials, which was similar to 4 and 15 times higher than those of Ag-BiVO4{010} and BiVO4, respectively. Scanning electron microscope (SEM) results revealed that the inactivation of E. coli bacteria is due to the breaking of their cell wall and leakage of the cytoplasm. Moreover, AgBr-Ag-BiVO4{010} also shows excellent photocatalytic activity in terms of tetracycline (TC) and Rhodamine B (RhB) degradation compared with BiVO4 and Ag-BiVO4{010}. On the basis of photoluminescence and photoelectrochemical analyses, we can deduce that the extraordinary photocatalytic activity of AgBr-Ag-BiVO4{010} is ascribed to the high separation efficiency of photogenerated charge carriers in the facet-heterojunction-based Z-scheme structure. The free radical trapping and electron paramagnetic resonance (EPR) spin-trap experiments disclosed that the active species in charge of organic degradation are h(+), (OH)-O-center dot, and O-center dot(2)-, while only h(+) and O-center dot(2)- take part in the inactivation of bacteria. We believe that this study paves a feasible way for constructing cost-efficient facet-heterojunction-based Z-scheme photocatalysts with high efficiency to remediate pathogenic bacteria and organic pollutants in wastewater.