Interface engineering in a nitrogen-rich COF/BiOBr S-scheme heterojunction triggering efficient photocatalytic degradation of tetracycline antibiotics

Tetracycline (TC) antibiotics, extensively utilized in livestock farming and aquaculture, pose significant environmental challenges. Photocatalysis, leveraging renewable sunlight and reusable photocatalysts, offers a promising avenue for mitigating TC pollution. However, identifying robust photocatalysts remains a formidable challenge. This study introduces a novel hollow-flower-ball-like nanoheterojunction composed of a nitrogen-rich covalent organic framework (N-COF) coupled with BiOBr (BOB), a semiconductor with a higher Fermi level. The synthesized N-COF/BOB S-scheme nanoheterojunction features an expanded contact interface, strengthened chemical bonding, and unique band topologies. The N-COF/BOB composites showcased exceptional TC degradation performance, achieving an 81.2% removal of 60 mg/L TC within 2 h, markedly surpassing the individual efficiencies of N-COF and BOB by factors of 3.80 and 5.96, respectively. Furthermore, the total organic carbon (TOC) removal efficiency highlights a superior mineralization capacity in the N-COF/BOB composite compared to the individual components, N-COF and BOB. The toxicity assessment revealed that the degradation intermediates possess diminished environmental toxicity. This enhanced performance is ascribed to the robust S-scheme nanoheterojunction structure, which promotes efficient photoinduced electron transfer from BOB to N-COF. This process also augments the separation of photogenerated charge carriers, resulting in an increased yield of superoxide radicals (∙O2-) and hydroxyl radicals (∙OH). These reactive species significantly contribute to the degradation and mineralization of TC. Consequently, this study introduces a sustainable approach for addressing emerging antibiotic contaminants, employing COF-based photocatalysts.

Effective Nanocomposite Based on Bi2MoO6/MoS2/AuNRs for NIR-II Light-Boosted Photodynamic/Chemodynamic Therapy

Bi₂MoO₆ (BMO) nanoparticles (NPs) have been widely used as a photocatalyst to decompose organic pollutants, but their potential for photodynamic therapy (PDT) is yet to be explored. Normally, the UV absorption property of BMO NPs is not suitable for clinical application because the penetration depth of the UV light is too small. To overcome this limitation, we rationally designed a novel nanocomposite based on Bi₂MoO₆/MoS₂/AuNRs (BMO-MSA), which simultaneously possesses both the high photodynamic ability and POD-like activity under NIR-II light irradiation. Additionally, it has excellent photothermal stability with good photothermal conversion efficiency. The as-prepared BMO-MSA nanocomposite could induce the germline apoptosis of Caenorhabditis elegans (C. elegans) via the cep-1/p53 pathway after being illuminated by light with a wavelength of 1064 nm. The in vivo investigations confirmed the ability of the BMO-MSA nanocomposite for the induction of DNA damage in the worms, and the mechanism was approved by determining the egl-1 fold induction in the mutants that have a loss of function in the genes involved in DNA damage response mutants. Thus, this work has not only provided a novel PDT agent, which may be used for PDT in the NIR-II region, but also introduced a new approach to therapy, taking advantage of both PDT and CDT effects.

Bismuth-Based Multi-Component Heterostructured Nanocatalysts for Hydrogen Generation

Developing a unique catalytic system with enhanced activity is the topmost priority in the science of H2 energy to reduce costs in large-scale applications, such as automobiles and domestic sectors. Researchers are striving to design an effective catalytic system capable of significantly accelerating H2 production efficiency through green pathways, such as photochemical, electrochemical, and photoelectrochemical routes. Bi-based nanocatalysts are relatively cost-effective and environmentally benign materials which possess advanced optoelectronic properties. However, these nanocatalysts suffer back recombination reactions during photochemical and photoelectrochemical operations which impede their catalytic efficiency. However, heterojunction formation allows the separation of electron–hole pairs to avoid recombination via interfacial charge transfer. Thus, synergetic effects between the Bi-based heterostructured nanocatalysts largely improves the course of H2 generation. Here, we propose the systematic review of Bi-based heterostructured nanocatalysts, highlighting an in-depth discussion of various exceptional heterostructures, such as TiO2/BiWO6, BiWO6/Bi2S3, Bi2WO6/BiVO4, Bi2O3/Bi2WO6, ZnIn2S4/BiVO4, Bi2O3/Bi2MoO6, etc. The reviewed heterostructures exhibit excellent H2 evolution efficiency, ascribed to their higher stability, more exposed active sites, controlled morphology, and remarkable band-gap tunability. We adopted a slightly different approach for reviewing Bi-based heterostructures, compiling them according to their applicability in H2 energy and discussing challenges, prospects, and guidance to develop better and more efficient nanocatalytic systems.

Synthesis and applications of bismuth-impregnated biochars originated from spent coffee grounds for efficient adsorption of radioactive iodine: A mechanism study

The adsorption of radioactive iodine, which is capable of presenting high mobility in aquatic ecosystems and generating undesirable health effects in humans (e.g., thyroid gland dysfunction), was comprehensively examined using pristine spent coffee ground biochar (SCGB) and bismuth-impregnated spent coffee ground biochar (Bi@SCGB) to provide valuable insights into the variations in the adsorption capacity and mechanisms after pretreatment with Bi(NO₃)₃. The greater adsorption of radioactive iodine toward Bi@SCGB (adsorption capacity (Q_e) = 253.71 μg/g) compared to that for SCGB (Q_e = 23.32 μg/g) and its reduced adsorption capability at higher pH values provide evidence that the adsorption of radioactive iodine with SCGB and Bi@SCGB is strongly influenced by the presence of bismuth materials and the electrostatic repulsion between their negatively charged surfaces and negatively charged radioactive iodine (IO₃^-). The calculated R² values for the adsorption kinetics and isotherms support that chemisorption plays a crucial role in the adsorption of radioactive iodine by SCGB and Bi@SCGB in aqueous phases. The adsorption of radioactive iodine onto SCGB was linearly correlated with the contact time (h^1/2), and the diffusion of intra-particle predominantly determined the adsorption rate of radioactive iodine onto Bi@SCGB (C_{stage II} (129.20) > C_{stage I} (42.33)). Thermodynamic studies revealed that the adsorption of radioactive iodine toward SCGB (ΔG° = -8.47 to -7.83 kJ/mol; ΔH° = -13.93 kJ/mol) occurred exothermically and that for Bi@SCGB (ΔG° = -15.90 to -13.89 kJ/mol; ΔH° = 5.88 kJ/mol) proceeded endothermically and spontaneously. The X-ray photoelectron spectroscopy (XPS) analysis of SCGB and Bi@SCGB before and after the adsorption of radioactive iodine suggest the conclusion that the change in the primary adsorption mechanism from electrostatic attraction to surface precipitation upon the impregnation of bismuth materials on the surfaces of spent coffee ground biochars is beneficial for the adsorption of radioactive iodine in aqueous phases.

Versatile superhydrophobic bismuth molybdate cotton fabric for oil/water separation and decompose dyestuff

Water pollution caused by the discharged insolubility petroleum contaminants and organic compound dyes seriously threatens the natural self-purity capacity of the water body and the survival of aquatic species, so it is imperative to restraint the deterioration of the aquatic environment. In this paper, pathways are propounded for the simultaneous removal of insoluble spilling oil and organic dye contaminants. Particularly, hydrophobic ZnSnO₃ after stearic acid modification and Bi₂MoO₆ photocatalysts are introduced into the cotton fabric substrate through solution dip-coating. The durability of the prepared fabric suffers from the acid-base corrosion, thermal treatment and mechanical wear, while still exhibiting remarkable water-repellent (WCA > 150°) property. Furthermore, the remarkable photocatalytic activity makes it possible for reusable degradation and the primary active species, namely the holes, to be verified by the radicals-capturing experiment. It is worth observing that as-prepared superhydrophobic fabric possesses admirable water-proof property and cycling durability of decomposing toxic water-soluble organic dye, thereby contributing to further realizing the ecological concept of clear waters.

Photocatalytic Hydrogen Production from Formic Acid Solution with Titanium Dioxide with the Aid of Simultaneous Rh Deposition

Photocatalytic hydrogen production was studied with a formic acid solution with titanium dioxide (TiO2) with the aid of simultaneous Rh deposition. The optimum conditions were as follows: Rh loading, 0.1 wt%; formic acid concentration, 1.0%; solution, pH 2.2; temperature, 50 °C. Under the optimum conditions, the photocatalytic hydrogen production with TiO2 by the simultaneous deposition of Rh was 5.0 mmol g−1, 12.2 mmol g−1 and 16.0 mmol g−1 after 1 h, 3 h and 5 h of irradiation time for black light, respectively. Rh/TiO2 photocatalysts were characterized by XRD, SEM, photoluminescence spectra, diffuse reflectance spectra and the BET surface area. The reaction mechanism of photocatalytic hydrogen production from formic acid by Rh/TiO2 was also proposed.

Composition-dependent activity of ZnxCd1-xSe solid solution coupled with Ni2P nanosheets for visible-light-driven photocatalytic H2 generation

Metal selenide semiconductors have been rarely used for photocatalytic water splitting because of their poor stability and severe photocorrosion properties. Hence, designing stable metal selenides with suitable bandgap energies has considerable practical significance in photocatalytic H₂ evolution. In this work, a novel series of Zn_xCd_1-xSe (x = 0 ∼ 1) with tunable band structure were fabricated through a simple solvothermal method. Impressively, the ZnSe exhibited a maximum H₂ production rate of 1056 µmol g^-1h^-1, which was higher than that of CdSe and Zn_xCd_1-xSe solid solutions. Such visible-light photoactivity for water reduction to H₂ was attained even after 6 cycling photocatalytic experiments. Moreover, the two-dimensional (2D) Ni₂P nanosheets act as a high-efficiency cocatalyst integrated with Zn_xCd_1-xSe semiconductor to boost photocatalytic H₂ generation performance. The optimal 8% Ni₂P/ZnSe composites displayed excellent cycling stability and superior photocatalytic H₂ evolution performance (4336 µmol g^-1h^-1), which was about 4.1 times that of pure ZnSe under visible light irradiation. Photoelectrochemical (PEC), photoluminescence (PL), and time-resolved photoluminescence (TRPL) measurements reveal that the improved photoactivity Ni₂P/ZnSe photocatalysts were ascribed to the effective separation and migration of photoinduced carriers. The present work paves a pathway to explore the fabrication of Zn_xCd_1-xSe solid solutions and the hybridization of 2D transition metal phosphides nanosheets toward photocatalytic applications.

Synthesis of Oxygen-Rich Bismuth Oxybromide (Bi24O31Br10) Photocatalyst for High Efficiency Degradation of Sulfadiazine Under Simulated Sunlight

At present, compared with other antibiotic degradation systems, there are few literatures on pho- tocatalytic degradation of sulfadiazine (SDZ). In this research, it was firstly discovered that the oxygen-rich bismuth oxybromide (Bi₂₄O₃₁ Br₁₀) photocatalyst can efficiently degrade SDZ under simulated sunlight. In this paper, the prepared Bi₂₄O₃₁Br₁₀ photocatalyst by mixed solvothermal method represented outstanding photocatalytic performance. The catalyst synthesized at 120 °C and pH = 10 showed optimum degradation function in the samples prepared at various temperatures and pH value. After 3 h of irradiation, 96.2% of SDZ solution could be decomposed. The effects of preparation conditions, catalyst dosage, initial SDZ concentration and initial SDZ pH value on photocatalytic degradation efficiency were investigated systematically. Besides, the effect of active species was studied by trapping tests, and it was concluded that 'O₂ contributes the most to the photocatalytic process. A possible photocatalytic degradation mechanism was proposed.

Construction of direct Z-scheme Bi5O7I/UiO-66-NH2 heterojunction photocatalysts for enhanced degradation of ciprofloxacin: Mechanism insight, pathway analysis and toxicity evaluation

Direct Z-scheme Bi₅O₇I/UiO-66-NH₂ (denoted as BU-x) heterojunction photocatalysts were successfully constructed through ball-milling method. Photocatalytic activities of the as-prepared BU-x samples were determined by using a typical fluoroquinolone antibiotic, ciprofloxacin (CIP). All BU-x heterojunctions exhibited better CIP removal performances than that of pristine Bi₅O₇I and UiO-66-NH₂ upon exposure to white light irradiation. In comparison, the heterojunction with UiO-66-NH₂ content of 50 wt% (BU-5) showed excellent structural stability and the optimal adsorption-photodegradation efficiency for the CIP removal. The removal efficiency of CIP (10 mg/L) over BU-5 (0.75 g/L) achieved 96.1% within 120 min illumination. Meanwhile, the effect of photocatalyst dosage, pH and inorganic anions were systemically explored. Reactive species trapping experiments, electron spin resonance (ESR) signals, Mott-Schottky measurements and density functional theory (DFT) simulation revealed that the photo-generated holes (h⁺), hydroxyl radical (·OH) and superoxide radical (·O₂^-) played crucial roles in CIP degradation. This result can be ascribed to that the unique Z-scheme charge transfer configuration retained the excellent redox capacities of Bi₅O₇I and UiO-66-NH₂. Meanwhile, the CIP degradation pathways and the toxicity of various intermediates were subsequently analyzed. This work provided a feasible idea for removing antibiotics by bismuth-rich bismuth oxyhalide/MOF-based heterostructured photocatalysts.

Highly Selective Production of Ethanol Over Hierarchical Bi@Bi2 MoO6 Composite via Bicarbonate-Assisted Photocatalytic CO2 Reduction

Photocatalytic CO₂ reduction is a sustainable and inexpensive method to solve the energy crisis and the greenhouse effect. However, the major stumbling blocks such as poor product selectivity, low yield of the multi-carbon products, and serious recombination of electron-hole pairs hinder practical application of photocatalysts. Herein, a high-performance Bi@Bi₂ MoO₆ photocatalyst, Bi nanoparticles grown on the surface of Bi₂ MoO₆ nanosheets with oxygen vacancies, was fabricated via a simple solvothermal approach. Benefiting from the abundant active sites and effective separation of photogenerated carriers of Bi₂ MoO₆ nanosheets, and the localized surface plasmon resonance effect of Bi nanoparticles, the Bi@Bi₂ MoO₆ sample exhibited great photocatalytic CO₂ reduction activity. Furthermore, adding NaHCO₃ into the system not only significantly increased the C₂ H₅ OH generation rate but also enhanced the product selectivity. In the photocatalytic measurement (0.17 mol L^-1 CO₂ -saturated NaHCO₃ solution), the highest formation rates of CO, CH₃ OH, and C₂ H₅ OH were reached at 0.85, 0.59, and 17.93 μmol g^-1  h^-1 (≈92 % selectivity), respectively.

Cocatalysts from types, preparation to applications in the field of photocatalysis

With the rapid development of society, the burden of energy and the environment is becoming more and more serious. Photocatalytic hydrogen production, the photosynthesis of organic fuel, and the photodegradation of pollutants are three effective ways to reduce these burdens using semiconductor photocatalysts. To improve the reaction efficiency of photocatalysts, a small amount of cocatalyst is often added when photocatalysts participate in the synthesis or decomposition reaction. The addition of this small amount of cocatalyst is like a finishing touch, significantly increasing the activity of the photocatalysts. However, in our common study of photocatalysis, we often pay attention to the study of photocatalysts but ignore the study of cocatalysts. Herein, we summarize the recent application research on cocatalysts in the field of photocatalysis, starting from the types, preparation methods, and reaction mechanisms among others, to remind researchers of the matters needing attention when using cocatalysts.

Polydopamine-Assisted Two-Dimensional Molybdenum Disulfide (MoS2)-Modified PES Tight Ultrafiltration Mixed-Matrix Membranes: Enhanced Dye Separation Performance

Tight ultrafiltration (TUF) membranes with high performance have attracted more and more attention in the separation of organic molecules. To improve membrane performance, some methods such as interface polymerization have been applied. However, these approaches have complex operation procedures. In this study, a polydopamine (PDA) modified MoS₂ (MoS₂@PDA) blending polyethersulfone (PES) membrane with smaller pore size and excellent selectivity was fabricated by a simple phase inversion method. The molecular weight cut-off (MWCO) of as-prepared MoS₂@PDA mixed matrix membranes (MMMs) changes, and the effective separation of dye molecules in MoS₂@PDA MMMs with different concentrations were obtained. The addition amount of MoS₂@PDA increased from 0 to 4.5 wt %, resulting in a series of membranes with the MWCO values of 7402.29, 7007.89, 5803.58, 5589.50, 6632.77, and 6664.55 Da. The MWCO of the membrane M3 (3.0 wt %) was the lowest, the pore size was defined as 2.62 nm, and the pure water flux was 42.0 L m⁻² h⁻¹ bar⁻¹. The rejection of Chromotrope 2B (C2B), Reactive Blue 4 (RB4), and Janus Green B (JGB) in aqueous solution with different concentrations of dyes was better than that of unmodified membrane. The separation effect of M3 and M0 on JGB at different pH values was also investigated. The rejection rate of M3 to JGB was higher than M0 at different pH ranges from 3 to 11. The rejection of M3 was 98.17–99.88%. When pH was 11, the rejection of membranes decreased with the extension of separation time. Specifically, at 180 min, the rejection of M0 and M3 dropped to 77.59% and 88.61%, respectively. In addition, the membrane had a very low retention of salt ions, Nacl 1.58%, Na₂SO₄ 10.52%, MgSO₄ 4.64%, and MgCl₂ 1.55%, reflecting the potential for separating salts and dyes of MoS₂@PDA/PES MMMs.

Constructing a 2D/2D heterojunction of MoSe2/ZnIn2S4 nanosheets for enhanced photocatalytic hydrogen evolution

2D/2D MoSe₂/ZnIn₂S₄ heterojunctions exhibit high photocatalytic activity owing to MoSe₂ as a cocatalyst, which provides more active sites, reducing the overpotential and the activation energy for water reduction.

Novel BP/BiOBr S-scheme nano-heterojunction for enhanced visible-light photocatalytic tetracycline removal and oxygen evolution activity

Designing heterojunction photocatalysts with strong interfacial interaction and matched band structure is an effective way to reduce the recombination of photogenerated carriers. Herein, the exfoliated black phosphorus (BP) nanosheets were coupled with BiOBr nanosheets having higher Fermi level, and thereby it constructed a novel layered BP/BiOBr nano-heterojunction with chemically bonding, larger contact interface and unique band structures. BiOBr nanosheets were self-assembled on the surface of BP nanosheets by a facile liquid-phase ultrasound combined with solvothermal method. The photocatalytic performance for tetracycline (TC) degradation, oxygen evolution and H₂O₂ production rate of Sol-10BP/BiOBr was 7.8, 7.0 and 2.6 times than that of pure BiOBr, respectively. The in-situ generated H₂O₂ and OH became the main active species of mineralization and decomposition of TC. The novel S-scheme two-dimensional BP/BiOBr nano-heterojunction for boosting spatial charge separation retained the useful holes-electrons with higher redox ability, which was very beneficial for producing more OH, H₂O₂ and O₂, and the photocatalytic activity was greatly improved.

Preparation, Characterization, and Performance Analysis of S-Doped Bi2MoO6 Nanosheets

S-doped Bi₂MoO₆ nanosheets were successfully synthesized by a simple hydrothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption isotherms, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), elemental mapping spectroscopy, photoluminescence spectra (PL), X-ray photoelectron spectroscopy (XPS), and UV-visible diffused reflectance spectra (UV-vis DRS). The photo-electrochemical performance of the samples was investigated via an electrochemical workstation. The S-doped Bi₂MoO₆ nanosheets exhibited enhanced photocatalytic activity under visible light irradiation. The photo-degradation rate of Rhodamine B (RhB) by S-doped Bi₂MoO₆ (1 wt%) reached 97% after 60 min, which was higher than that of the pure Bi₂MoO₆ and other S-doped products. The degradation rate of the recovered S-doped Bi₂MoO₆ (1 wt%) was still nearly 90% in the third cycle, indicating an excellent stability of the catalyst. The radical-capture experiments confirmed that superoxide radicals (·O^2-) and holes (h⁺) were the main active substances in the photocatalytic degradation of RhB by S-doped Bi₂MoO₆.

In situ construction of WO3 nanoparticles decorated Bi2MoO6 microspheres for boosting photocatalytic degradation of refractory pollutants

Visible-light-driven (VLD) heterojunction photocatalysts for refractory contaminant degradation have aroused huge interest because of their outstanding photocatalytic performance. From the aspect of practical application, it is important to develop a highly efficient, durable, eco-friendly and inexpensive VLD photocatalyst. Herein, we report a novel VLD WO₃/Bi₂MoO₆ heterojunction photocatalyst with remarkable photocatalytic activity, which was fabricated via an electrospinning-calcination-solvothermal route. The phase, composition, morphologies, and optical properties of WO₃/Bi₂MoO₆ heterojunctions were comprehensively characterized. The photocatalytic performance of WO₃/Bi₂MoO₆ heterojunctions was assessed by the removal of rhodamine (RhB) and tetracycline hydrochloride (TC) under visible light (VL). WO₃/Bi₂MoO₆ heterojunctions displayed superior photocatalytic activities compared to Bi₂MoO₆, WO₃, or the mechanical mixture of WO₃ and Bi₂MoO₆. In particular, the heterojunction material (0.4WB, theoretical molar ratio of WO₃/Bi₂MoO₆ is 0.4/1.0) exhibited the best degradation efficiency (100%) and mineralization rate (52.3%) in 90 min, both of which exceeded the observed rates for Bi₂MoO₆ by 5.3 and 6.4 times, respectively. Moreover, 0.4WB showed a good durability in eight runs. The optimized photocatalytic property of WO₃/Bi₂MoO₆ can be attributed to enhanced VL absorption and reduced recombination efficiency of carriers owing to the synergistic effects between Bi₂MoO₆ and WO₃. The necessity of direct contact between WO₃/Bi₂MoO₆ and contaminants was experimentally verified. The study on photocatalytic mechanism demonstrates that superoxide free radicals (O₂^-) and photo-generated hole (h⁺) are dominantly responsible for the pollutant degradation, as demonstrated by the trapping experiments and electron spin resonance (ESR) analysis. Therefore, the WO₃/Bi₂MoO₆ heterojunction holds huge potential to be utilized as a durable and highly active photocatalyst for wastewater treatment.

Preparation of monolayer HSr2Nb3O10 nanosheets for photocatalytic hydrogen evolution

Monolayer HSr₂Nb₃O₁₀ nanosheets modified with highly dispersed Pt clusters were prepared via in situ growth to promote an excellent photocatalytic hydrogen evolution activity.