Facile Fabrication of Flower-Like BiOI/BiOCOOH p-n Heterojunctions for Highly Efficient Visible-Light-Driven Photocatalytic Removal of Harmful Antibiotics

Synthesis and Visible Light Catalytic Performance of BiOI/Carbon Nanofibers Heterojunction

Semiconductor materials as photocatalysts hold great prospects for renewable energy substitutes and environmental protection. Nanostructured BiOX (X=Cl, Br, I) with favorable features of a unique layered crystal structure and suitable band gaps has been demonstrated to be a promising photocatalytic material. In this paper, a two-step synthesis route combining an electrospinning technique and SILAR reaction has been accepted as a straightforward protocol for the exploitation of BiOI/carbon nanofibers’ (CNFs) hierarchical heterostructures. As expected, the BiOI/CNFs presented a much higher degradation rate of methyl orange than that of the pure BiOI under visible light. The degradation rate of methyl orange reaches 85% within 210 min. The enhanced photocatalytic activity could be attributed to the fact that conductive CNFs as substrate could effectively improve the separation and transformation of photogenerated charges. Moreover, the fabricated BiOI/CNFs after five cycles could be easily recycled without a decrease in photocatalytic activity due to their ultra-long one-dimensional nano-structural property.

Type II Heterojunction Formed between {010} or {012} Facets Dominated Bismuth Vanadium Oxide and Carbon Nitride to Enhance the Photocatalytic Degradation of Tetracycline

Both type II and Z schemes can explain the charge transfer behavior of the heterojunction structure well, but the type of heterojunction structure formed between bismuth vanadium oxide and carbon nitride still has not been clarified. Herein, we rationally prepared bismuth vanadium oxide with {010} and {012} facets predominantly and carbon nitride as a decoration to construct a core-shell structure with bismuth vanadium oxide wrapped in carbon nitride to ensure the same photocatalytic reaction interface. Through energy band establishment and radical species investigation, both {010} and {012} facets dominated bismuth vanadium oxide/carbon nitride composites exhibit the type II heterojunction structures rather than the Z-scheme heterojunctions. Furthermore, to investigate the effect of type II heterojunction, the photocatalytic tetracycline degradations were performed, finding that {010} facets dominated bismuth vanadium oxide/carbon nitride composite demonstrated the higher degradation efficiency than that of {012} facets, due to the higher conduction band energy. Additionally, through the free radical trapping experiments and intermediate detection of degradation products, the superoxide radical was proven to be the main active radical to decompose the tetracycline molecules. Therein, the tetracycline molecules were degraded to water and carbon dioxide by dihydroxylation-demethylation-ring opening reactions. This work investigates the effect of crystal planes on heterojunction types through two different exposed crystal planes of bismuth vanadate oxide, which can provide some basic research and theoretical support for the progressive and controlled synthesis of photocatalysts with heterojunction structures.

One-dimensional recoverable ZnFe2O4/C/MnO2/BiOI magnetic composite with enhanced photocatalytic performance for organic dyes degradation

Excessive discharge of toxic dyes is detrimental to ecological system and human health. Therefore, an effective photocatalyst must be designed and developed to degrade dyes from wastewater. Herein, a novel one-dimensional (1D) flower-like recoverable ZnFe₂O₄/C/MnO₂/BiOI magnetic composite photocatalyst was synthesized via electrospinning technique combined with hydrothermal method. The photocatalytic activities of composite photocatalyst were evaluated by degrading methyl orange (MO) and Rhodamine B (RhB) under simulated light irradiation. The efficiency of ZnFe₂O₄/C/MnO₂/BiOI photocatalyst in visible light for 150 min reached 91% (MO) and 120 min reached 94% (RhB). Moreover, the degradation rate of MO still remained 78% after five cycles. The design of 1D magnetic flower-like composite provided a new strategy for preparing photocatalysts possessing excellent photocatalytic efficiency and cyclic stability.