In₂O₃ Nanoparticle/Bi₄O₅Br₂ Nanosheet S-Scheme Heterojunctions with Interfacial Oxygen Vacancies for Photocatalytic Degradation of Tetracycline

Abstract

The development of highly efficient photocatalysts for antibiotics contamination in water remains a severe challenge. In this study, In2O3 nanoparticle/Bi4O5Br2 nanosheet S-scheme heterojunction with interface oxygen vacancies (OVs) was constructed by a hydrothermal-calcination approach and a simple chemical precipitation process. Under simulated sunlight, this composite showed enhanced degradation efficiency for tetracycline hydrochloride (TCH) with 92.4%, which was much higher than those of pure Bi4O5Br2 (50.2%) and In2O3 (28.6%). The excellent removal efficiency was mainly attributed to the synergistic effect of S-scheme heterojunctions and interface OVs accelerating the complexation of unwanted electrons (e–) and holes (h+), thus retaining e– with the strong oxidizing ability and h+ with the strong reducing ability to participate in the reaction. In addition, the abundant OVs in In2O3 nanoparticles/Bi4O5Br2 nanosheets could enhance the adsorption of O2 and promote the generation of superoxide radicals (·O2 –). The toxicity of the tetracycline degradation products and the catalyst was evaluated by E. coli growth inhibition experiments. Based on the TCH intermediates detected by HPLC-MS, three possible TCH degradation pathways were proposed. This study shows that the construction of S-scheme heterojunctions with interfacial defects is an effective strategy for the preparation of efficient photocatalysts.

Generation of •OH and •O2– Radicals by a Bi2O3-Nanoparticle/Bi4O5Br2 Type-II Heterojunction for Photocatalytic Degradation of Organic Molecules

“…The result of ESR spectra of TEMPO-h + proved this point (Figure d). Compared with Bi 4 O 5 Br 2 , the ESR peak intensity of TEMPO in BOB4 is found to decrease, suggesting a higher production of h + by BOB4 during the photocatalytic reaction . Therefore, the ESR data well support the results of the above quenching experiments.…”

“…To date, several mechanisms have been reported to elucidate the enhancements in photocatalytic activities achieved through the implementation of semiconductor heterojunctions, including type-II, p–n heterojunction, Z-scheme, and S-scheme structures . Over the past few years, many coupling photocatalysts based on Bi 4 O 5 Br 2 have been reported, including heterojunctions between Bi 4 O 5 Br 2 and MoS 2 , , WO 3 , FeVO 4 , CdS, BiOBr, Bi 12 O 17 Br 2 , Bi 4 O 5 I 2 , Mo 2 C, and g-C 3 N 5 . , Chang et al reported hierarchical Z-scheme Bi 2 S 3 /Bi 4 O 5 Br 2 heterojunctions synthesized by an anion-exchange method with preparations of Bi 4 O 5 Br 2 hierarchical clusters as a precursor . It was shown that the coupling composite exhibits a remarkable enhancement in the removal of NO x and selectivity toward NO 2 – /NO 3 – in comparison to Bi 4 O 5 Br 2 .…”

“…However, synthesis of these reported Bi 4 O 5 Br 2 -based heterojunctions involves tedious two-step routes, − namely, preparation of a Bi 4 O 5 Br 2 matrix, followed by partial anion exchange, in situ growth, or loading of another component on surfaces of the Bi 4 O 5 Br 2 matrix to form the heterojunctions; this actually limits the heterojunction interface area and stability and thus enhances the photocatalytic activity. , Therefore, it is necessary to probe more simple ways to synthesize the Bi 4 O 5 Br 2 -based heterojunctions with a large interface area. In addition, most of the reported Bi 4 O 5 Br 2 -based heterojunctions are S-scheme (or direct all-solid-state Z-scheme), − ,− and type-II Bi 4 O 5 Br 2 -based heterojunctions are very few. , …”

Fenton-like Catalysts Based on Graphitic Carbon Nitride Nanosheets Decorated with Fe3O4 Nanoparticles for Removal of Colorless Tetracycline

“…Intermediate products of TC degradation during the Fenton-like reaction were confirmed by HR-MS, and the results are presented in Figure S7. Different products were identified from the figure, and possible degradation pathways were proposed, as shown in Figure . , In pathway 1, the TC fragment ( m / z = 445) is transmuted into product 1 (P1; m / z = 476), and product 2 (P2; m / z = 431) via the loss of the N -dimethyl group due to the continuous attack of reactive oxygen species. Subsequently, more such groups become dissociated from the TC molecules as the reaction continues (P4; m / z = 339), which form due to the ring opening of TC by the reactive oxygen species.…”

S-Scheme Heterostructured CdS/g-C3N4 Nanocatalysts for Piezo-Photocatalytic Synthesis of H2O2

“…Based on the existing relationship between solid samples, the XPS instrument can provide the formula, as presented in the Supporting Information, to calculate the material’s work function, in which the contact potential difference (Δ V ) can be used to obtain the value. Δ V is defined as the distance between two inflection points in XPS-VB measurements. , The Δ V value of CN and CdS was 1.68 and 0.87 eV, respectively, leading to a work function value of 6.56 eV for CN and 4.75 eV for CdS.…”