Visible Light Absorption Range Research Articles

TiO2 embedded in AC-COFs/SiO2 composites with core-shell structure for improved photocatalytic degradation performance of tetracycline

The excellent photocatalytic properties of covalent organic frameworks (COFs) and Titanium dioxide (TiO2) have been a hot research topic. However, the extensive application of the COFs and TiO2 in photocatalysis is restricted by their easy agglomeration and poor visible light usage, respectively. In this research, acyl chloride-covalent organic frameworks (AC-COFs) prepared by ultrasound assisted synthesis method was attached to the surface of silica oxides (SiO2) prepared by the modified Stöber method with high specific surface area and high porosity through amino groups to form a core-shell structure, which effectively solved the problem of easy agglomeration of the AC-COFs. Subsequently, TiO2 was loaded onto the surface of the AC-COFs@SiO2 composites to create high-performing TiO2/AC-COFs@SiO2 composites with a wide visible light absorption range (λ=409 nm), a narrow band gap (Eg=2.32 eV) and strong adsorption performance (Qm=314.47 mg/g). Compared with SiO2, the adsorption performance of this composite material was improved by 1.5 times. Meanwhile, the formed binary heterogeneous structure effectively reduces carrier recombination rate and releases more active substances like h+ and ·OH, so the catalyst has excellent self-cleaning and cyclic stability under the combined effect of adsorption and photocatalysis. It was found that tetracycline (TC) completely degrades after 50 min and the degradation rate decreasing by only 2.8 % after six cycles.

Investigation of the mechanism and stability of highly efficient photocatalytic degradation of Methylene blue using Ni doped CdS photocatalyst

Methylene blue (MB) is commonly utilized in chemical indicators, dyes, biological colors, and pharmaceuticals. Its aqueous solution is poisonous and carcinogenic, posing a significant threat to the ecological environment. The wurtzite-phase NixCd1−xS was synthesized using the hydrothermal technique in this study. Ni doped CdS enhanced its photocatalytic efficiency and resistance to photocorrosion, enabling its application in the photocatalytic destruction of MB. The incorporation of Ni did not change the crystal structure and microstructure of CdS, but increased the visible light absorption range and decreased the band gap width slightly, which promoted the migration of photogenerated electrons and reduced their recombination with holes, resulting in higher photogenerated carrier separation efficiency of NixCd1−xS. The photocatalytic decolorization rate of Ni0.06Cd0.94S for 100 mL of 10 mg/L MB at 240 min is 91.3 %, and the reaction rate constant is 0.01102 min−1, which is 4.42 times that of wurtzite-phase CdS. The photocatalytic mechanism of NixCd1−xS and its composite was analyzed using trap experiments in conjunction with the band structure of the sample. Additionally, the stability of NixCd1−xS was evaluated. The results indicated that the stability was superior to that of CdS. The findings demonstrate that Ni0.06Cd0.94S exhibits good catalytic activity and stability, making it a viable catalyst for the photocatalytic degradation of organic pollutants in water.

Design of a novel direct Z-scheme BiOIO3/Bi2WO6 heterojunction for enhanced photocatalytic degradation of norfloxacin under visible light

The unique electronic structure, appropriate bandgap energy, and excellent electron transfer capability make bismuth-based semiconductors hotspots in the field of photocatalysis. Novel BiOIO3/Bi2WO6 Z-scheme heterojunctions were fabricated via in-situ hydrothermal synthesis. The BIOBIW-3 heterojunctions (BiOIO3:Bi2WO6=0.25:0.8, mole ratio) exhibited excellent photocatalytic activity for norfloxacin (NOR), with a degradation efficiency of 90.41 % after 90 min of photoreaction and a reaction kinetic constant of 0.02132 min−1, which was 5.02 and 9.35 times higher than that of BIO and BIW, respectively. The superior photocatalytic performance can be attributed to the intimate interface between BiOIO3 and Bi2WO6, as well as the staggered energy band structure that facilitates the formation of a Z-type heterojunction. This not only widens the range of visible light absorption but also enhances the separation and transfer of photogenerated carriers while maintaining a high capacity for redox reactions. The dominant active species in the degradation process were photogenerated holes (h+) and superoxide (∙O2−) radicals, and an in-depth exploration of the possible mechanism was conducted. Furthermore, the effects of various parameters, including solution pH, catalyst dosage, and NOR concentration on the photocatalytic degradation of NOR were also investigated. The prepared BiOIO3/Bi2WO6 heterojunctions exhibited remarkable photocatalytic performance and chemical stability, presenting a novel research direction for employing layered bismuth-based materials in the degradation of fluoroquinolone antibiotic wastewater.

Ag-bridged Z-scheme AgI/NU-1000 heterojunction for enhanced photocatalytic degradation of sulfamethazine: Pathways, mechanism insight, and DFT calculations

Constructing heterojunction structures is a crucial approach for improving carrier separation efficiency and expanding the visible-light absorption range of photocatalysts. Herein, a series of Ag-bridged Z-scheme (AgI/NU-1000) heterojunction photocatalysts were successfully prepared using a simple in-situ precipitation method. The photodegradation efficiency of the AgI/NU-1000 samples was assessed by degrading sulfamethazine under visible-light conditions. The optimized AgI/NU-10000.35 (AN-2) photocatalyst exhibited exceptional photodegradation activity, achieving a degradation rate of 89.68 % within 40 min. The toxicity test results proved that the solution degraded by AN-2 exhibited no detrimental effects on biological growth, thereby demonstrating its potential practical application value. Electrochemical and photochemical tests demonstrated that the creation of a Z-scheme heterojunction was favorable for the separation of photogenerated carriers. Density functional theory (DFT) calculations and X-ray photoelectron spectroscopy were used to clarify the electron migration direction within the AgI/NU-1000 heterojunction. Possible degradation pathways and mediate products were investigated using high-performance liquid chromatography–mass spectrometry and DFT calculations. This work demonstrates the potential application of AgI/NU-1000 composite materials in environmental treatment.

Solvothermal preparation of CuO/g-C3N4 and photocatalytic degradation of ciprofloxacin

Composite materials CuO/g-C3N4 (CuOCN) were prepared using a solvothermal method to investigate their degradation effect on ciprofloxacin (CIP). The materials were characterized through X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectrophotometry (DRS), and X-ray photoelectron spectroscopy (XPS). The toxicity of degradation products of CIP was assessed through antibacterial experiments, and the degradation mechanism of CIP was investigated using quenching agent capture and high-performance liquid chromatography-mass spectrometry (HPLC-MS). The results of XRD and FTIR indicate that the CuOCN composite has been successfully synthesized. The photocatalytic experiment shows that adding 15% (w/w) of Cu3(BTC)2(H2O)3 in melamine (CuOCN2) has a relatively good degradation effect on CIP and can be reused multiple times. The TEM results indicate that both CuO and g-C3N4 have a layered structure and are attached together. HRTEM analysis reveals that the two components in CuOCN2 are arranged in a layered structure, with CuO displaying two crystal planes. Energy Dispersive Spectrometer (EDS) analysis reveals that the proportion of CuO in the three composite materials is 7.86% (w/w), 15.93% (w/w), and 84.83% (w/w), respectively. DRS detection reveals that the greater the amount of CuO added, the broader the visible light absorption range of the composite material, and the narrower the bandgap width. The photocurrent and photoresistance indicate that CuOCN2 exhibits a good photoelectric effect. XPS analysis shows that the CuOCN2 composite material possesses both the chemical composition and structure of CuO and g-C3N4. During the catalytic degradation process of CIP, four active substances, h+, e−, ·O2 −, and ·OH, were produced, leading to a reduction in the toxicity of the degradation products. Through HPLC-MS analysis, it was found that CIP undergoes reactions such as defluorination, ring opening of piperazine, and quinolone during degradation, resulting in reduced toxicity. This study provides an experimental basis for the degradation of CIP by CuOCN2.

2D/2D Heterojunctions of Layered TiO2 and (NH4)2V3O8 for Sunlight-Driven Methylene Blue Degradation

Photocatalysis based on titanium dioxide (TiO2) has become a promising method to remediate industrial and municipal effluents in an environmentally friendly manner. However, the efficiency of TiO2 is hampered by problems such as rapid electron–hole recombination and limited solar spectrum absorption. Furthermore, the sensitization of TiO2 through heterojunctions with other materials has gained attention. Vanadium, specifically in the form of ammonium vanadate ((NH4)2V3O8), has shown promise as a photocatalyst due to its ability to effectively absorb visible light. However, its use in photocatalysis remains limited. Herein, we present a novel synthesis method to produce lamellar (NH4)2V3O8 as a sensitizer in a supramolecular hybrid photocatalyst of TiO2–stearic acid (SA), contributing to a deeper understanding of its structural and magnetic characteristics, expanding the range of visible light absorption, and improving the efficiency of photogenerated electron–hole separation. Materials, such as TiO2–SA and (NH4)2V3O8, were synthesized and characterized. EPR studies of (NH4)2V3O8 demonstrated their orientation-dependent magnetic properties and, from measurements of the angular variation of g-values, suggest that the VO2+ complexes are in axially distorted octahedral sites. The photocatalytic results indicate that the 2D/2D heterojunction layered TiO2/vanadate at a ratio (1:0.050) removed 100% of the methylene blue, used as a model contaminant in this study. The study of the degradation mechanism of methylene blue emphasizes the role of reactive species such as hydroxyl radicals (•OH) and superoxide ions (O2•−). These species are crucial for breaking down contaminant molecules, leading to their degradation. The band alignment between ammonium vanadate ((NH4)2V3O8) and TiO2–SA, shows effective separation and charge transfer processes at their interface. Furthermore, the study confirms the chemical stability and recyclability of the TiO2–SA/(NH4)2V3O8 photocatalyst, demonstrated that it could be used for multiple photocatalytic cycles without a significant loss of activity. This stability, combined with its ability to degrade organic pollutants under solar irradiation, means that the TiO2–SA/(NH4)2V3O8 photocatalyst is a promising candidate for practical environmental remediation applications.

Visible light responsive photocatalytic fuel cell with Ce-UiO-66/g-C3N4/Bi2WO6/Ti photoanode for simultaneous degradation of rhodamine B and electricity generation

In order to enhance the carrier separation efficiency and redox ability of photoanode, a dual Z-scheme heterojunction Ce-UiO-66/g-C3N4/Bi2WO6/Ti photoanode was prepared and assembled with Cu cathode to form PFC. The characterization results show that Ce-UiO-66/g-C3N4/Bi2WO6 uniformly distributed on the Ti substrate, with average crystallite size of 9.04 nm and average particle size of 33.05 nm, which provides sufficient reactive active sites for RhB degradation. The RhB degradation rate, Pmax, Jsc, Voc and FF of the PFC were 90.9 % (90 min), 7.53 µW cm-2, 0.152 mA cm-2, 0.37 V and 0.134, respectively. The turnover frequency (TOF) for RhB degradation by the PFC reached 0.98 h-1. Fermi energy level analysis shows that a double-Z heterojunction is formed between Bi2WO6 and g-C3N4, and between Bi2WO6 and Ce-UiO-66, which not only effectively separates photogenerated e--h+, but also retains the high redox ability of the composite. Moreover, with the introduction of Ce-UiO-66, the composite photoanode has larger specific surface area and wider visible light absorption range. In addition, because of the built-in electric field, the photogenerated electrons can migrate to the surface of composite particles more easily and react with dissolved oxygen to generate more •O2- to participate in the degradation of RhB. This work provides a valuable reference for developing PFC photoanode with high efficiency and visible light response.

A Visible Light-Responsive TiO2 Photocathode Achieved by a Rh Dopant.

Developing an efficient and stable photocathode material for photoelectrochemical solar water splitting remains challenging. Herein, we demonstrate the potential of rutile TiO2 as a photocathode by Rh doping with visible light absorption up to 640 nm and an onset potential of 0.9 V versus the reversible hydrogen electrode. The dopant transforms the rutile host from an n-type semiconductor to a p-type one, as confirmed by the Mott-Schottky curve and kelvin probe force microscopy. Physical and photoelectrochemical analyses further suggest that the doping mechanism is dependent on concentration. Lower levels of dopants generate localized Rh3+, while higher levels favor Rh4+ that interacts more strongly with the O 2p orbitals. The latter is found not only to extend the visible light absorption range but also to facilitate charge transport. This work elucidates the role of the Rh dopant in adjusting the photoelectrochemical behavior of TiO2, and it provides a promising photocathode material for solar energy conversion.

Integrating bimetallic borides with g-C3N4 containing cyanamide defects for efficient photocatalytic nitrogen fixation

The sustainable generation of ammonia by photocatalytic nitrogen fixation under mild conditions is fascinating compared to conventional industrial processes. Nevertheless, owing to the low charge transfer efficiency, the insufficient light absorption capacity and limited active sites of the photocatalyst cause the difficult adsorption and activation of N2 molecules, thereby resulting in a low photocatalytic conversion efficiency. Herein, a novel bimetallic CoMoB nanosheets (CoMoB) co-catalyst modified carbon nitride with dual moiety defects (CN-TH3/3) Schottky junction photocatalyst is designed for photocatalytic nitrogen reduction reaction (NRR). The photocatalytic nitrogen reduction rate of the optimized CoMoB/CN-TH3/3 photocatalyst is 4.81 mM·g−1·h−1, which is 6.2 and 2.2 times higher than carbon nitride (CN) (0.78 mM·g−1·h−1) and CN-TH3/3 (2.21 mM·g−1·h−1), respectively. The excellent photocatalytic NRR performance is ascribed not only to the introduction of dual moiety defects (cyano and cyanamide groups) that extends the visible light absorption range and promotes exciton polarization dissociation, but also to the formation of interfacial electric field between CoMoB and CN-TH3/3, which effectively facilitates the interfacial charge transfer. Thus, the synergistic interaction between CN-TH3/3 and CoMoB further increases the electron numble of CoMoB active sites, which effectively strengthens the adsorption and activation of N2 and weakens the NN triple bond, thereby enhancing the photocatalytic NRR activity. This work highlights the introduced dual moiety defects and bimetallic CoMoB co-catalyst to synergistically enhance the photocatalytic nitrogen reduction performance.

A novel noble-metal-free FeS2/Mn0.5Cd0.5S heterojunction for enhancing photocatalytic H2 production activity: Carrier separation, light absorption, active sites

BackgroundThe development of efficient and noble-metal-free photocatalysts is greatly essential for photocatalytic hydrogen production. However, the photocatalytic activity of a single photocatalyst is usually limited for various reasons. MethodsHerein, FeS2/Mn0.5Cd0.5S (FSMCS) heterojunctions were constructed by a simple solvent evaporation method. The morphological characterizations revealed a raspberry-like hollow microsphere structure for FeS2 and irregular granularity for Mn0.5Cd0.5S. Photoluminescence (PL) and electrochemical experiments indicated that the FSMCS composite effectively facilitated the separation of photogenerated electron-hole pairs. The UV–vis diffuse reflectance spectrum (DRS) showed that, in FSMCS composite, the visible light absorption range was effectively expanded to the full visible light. Significant findingsExcellent photocatalytic activity in FSMCS heterojunctions without loading noble metals because FeS2 could serve an active site for hydrogen production. The optimum FSMCS composite had excellent photocatalytic hydrogen production activity (6.1 mmol·g−1·h−1), which was 5.6 and 2.3 times higher than that of the pristine Mn0.5Cd0.5S (1.1 mmol·g−1·h−1) and Mn0.5Cd0.5S-1 %Pt (2.7 mmol·g−1·h−1). Meanwhile, in four round-robin tests, the activity of the 5FSMCS photocatalyst did not significantly decrease. This work proved that combining Mn0.5Cd0.5S and non-precious metal cocatalysts to construct heterojunctions is a promising strategy for photocatalytic hydrogen production.

Enhanced photocatalytic activities of FCNO nanoparticles on graphitic carbon nitride

Efficient charge separation and broadened light absorption are of crucial importance for photocatalytic environmental remediation, and graphitic carbon nitride (g-C3N4) is a very promising photocatalyst for this purpose. Herein, the synthesis of FCNO nanoparticles embedded within graphitic carbon nitride (g-C3N4) by hydrothermal route assisted with pyrolysis of urea was presented. The g-C3N4 was obtained from an abundantly available precursor urea and the synthesis process played double role. Urea reacted with metal salts to convert them into metallic oxides and yielded g-C3N4. The experimental results revealed the in-situ fabrication of FCNO nanoparticles and formation of g-C3N4. The band gap narrowing made it possible that the samples were able to show a wide range of visible light absorption which made them suitable for photocatalytic activity studies. Thus, the materials were utilized for the visible light-based photocatalytic degradation of methylene blue dye. Photocatalytic degradation efficiency with ~93 % was achieved by the composite FCNO/g-C3N4 (50:50). The present approach for the synthesis of materials was proved to be cost-effective and time saving which enabled their use as recyclable photocatalyst.

Dual Z-scheme heterojunction Ce2Sn2O7/Ag3PO4/V@g-C3N4 for increased photocatalytic degradation of the food additive tartrazine, in the presence of persulfate: Kinetics, toxicity, and density functional theory studies

This study involved the synthesis of a Ce2Sn2O7/Ag3PO4/V@g-C3N4 composite through hydrothermal methods, followed by mechanical grinding. The resulting heterojunction exhibited improved catalytic activity under visible light by effectively separating electrons and holes (e−/h+). The degradation of Tartrazine (TTZ) reached 93.20% within 50 min by employing a ternary composite at a concentration of 10 mg L−1, along with 6 mg L−1 of PS. The highest pseudo-first-order kinetic constant (0.1273 min−1 and R2 = 0.951) was observed in this system. The dual Z-scheme heterojunction is developed by Ce2Sn2O7, Ag3PO4, and V@g-C3N4, and it may increase the visible light absorption range while also accelerating charge carrier transfer and separation between catalysts. The analysis of the vulnerability positions and degradation pathways of TTZ involved the utilization of density functional theory (DFT) and gas chromatography-mass spectrometry (GC-MS) to examine the intermediate products. Therefore, Ce2Sn2O7/Ag3PO4/V@g-C3N4 is an excellent ternary nanocomposite for the remediation of pollutants.

Interlayer Potassium Single-Atom-Coordinated g-C3N4 for Significantly Boosted Visible Light Photocatalytic H2 Production.

In recent years, graphitic carbon nitride (g-C3N4) has attracted considerable attention because it includes earth-abundant carbon and nitrogen elements and exhibits good chemical and thermal stability owing to the strong covalent interaction in its conjugated layer structure. However, bulk g-C3N4 has some disadvantages of low specific surface area, poor light absorption, rapid recombination of photogenerated charge carriers, and insufficient active sites, which hinder its practical applications. In this study, we design and synthesize potassium single-atom (K SAs)-doped g-C3N4 porous nanosheets (CM-KX, where X represents the mass of KHP added) via supramolecular self-assembling and chemical cross-linking copolymerization strategies. The results show that the utilization of supramolecules as precursors can produce g-C3N4 nanosheets with reduced thickness, increased surface area, and abundant mesopores. In addition, the intercalation of K atoms within the g-C3N4 nitrogen pots through the formation of K-N bonds results in the reduction of the band gap and expansion of the visible-light absorption range. The optimized K-doped CM-K12 nanosheets achieve a specific surface area of 127 m2 g-1, which is 11.4 times larger than that of the pristine g-C3N4 nanosheets. Furthermore, the optimal CM-K12 sample exhibits the maximum H2 production rate of 127.78 μmol h-1 under visible light (λ ≥ 420 nm), which is nearly 23 times higher than that of bare g-C3N4. This significant improvement of photocatalytic activity is attributed to the synergistic effects of the mesoporous structure and K SAs doping, which effectively increase the specific surface area, improve the visible-light absorption capacity, and facilitate the separation and transfer of photogenerated electron-hole pairs. Besides, the optimal sample shows good chemical stability for 20 h in the recycling experiments. Density functional theory calculations confirm that the introduction of K SAs significantly boosts the adsorption energy for water and decreases the activation energy barrier for the reduction of water to hydrogen.

All-organic heterojunctions used for the excellent photocatalytic H2O2 synthesis: The key role of bay-position Cl in PDI

Melem is the basic structural unit of g-C3N4. When directly utilized as a photocatalyst, the separation efficiency of photogenerated electron-hole pairs is low. In this study, we constructed a Melem-based all-organic heterojunction (PICN) by reacting the -NH2 at the terminal of the Melem unit with the anhydride of PDA. The photocatalytic efficiency for H2O2 production of the heterojunction is 4.2 times that of CN. Introducing -Cl at the bay position of PDI further enhances the photocatalytic H2O2 production efficiency by 1.6 times. This enhancement is attributed to the introduction of -Cl, which not only broadens the UV–visible light absorption range of the sample but also improves the interface electron transfer efficiency between Melem and PDICl. Moreover, the introduction of -Cl can also reduce the overpotential of the O2 reduction reaction on the surface of the sample. These novel findings may provide insights for the design of organic heterojunction photocatalysts.

Facile fabrication of CeO2/L-Bi2O2CO3 composite photocatalyst for removal of ciprofloxacin under visible light irradiation

The application of semiconductor photocatalytic technology to degrade antibiotics in water has been proved to be a promising technology CeO2/L-Bi2O2CO3 composite photocatalyst was efficiently prepared by a facile room temperature precipitation technique and employed in the photocatalytic degradation of ciprofloxacin (CIP). When the concentration of ciprofloxacin was 20 mg/L and the dosage of catalyst was 1.0 g/L, the degradation rate of CIP was 89.96 % after 120 min reaction with optimal catalyst. The addition of L-cysteine not only changed the crystallinity of Bi2O2CO3, but also broadened its visible light absorption range. Additionally, the combination of CeO2 and L-Bi2O2CO3 creates a heterojunction interface accelerates the electron transfer, thereby improving the photocatalytic activity. The degradation process was confirmed to involve the significant participation of O2– and h+ through free radical capture experiments. HPLC-MS analysis detected the intermediates of CIP degradation, leading to the proposition of two potential degradation pathways. Moreover, an electron transfer mechanism was suggested by analyzing the Mott-Schottky (M−S) curve and Taut-plot curves. This work provides new paradigm for the rational design of modified Bi2O2CO3-based photocatalysts and the treatment of contain CIP wastewater.

Bifunctional Co3O4/g-C3N4 Hetrostructures for Photoelectrochemical Water Splitting.

This study explored the synergistic potential of photoelectrochemical water splitting through bifunctional Co3O4/g-C3N4 heterostructures. This novel approach merged solar panel technology with electrochemical cell technology, obviating the need for external voltage from batteries. Scanning electron microscopy and X-ray diffraction were utilized to confirm the surface morphology and crystal structure of fabricated nanocomposites; Co3O4, Co3O4/g-C3N4, and Co3O4/Cg-C3N4. The incorporation of carbon into g-C3N4 resulted in improved catalytic activity and charge transport properties during the visible light-driven hydrogen evolution reaction and oxygen evolution reaction. Optical properties were examined using UV-visible spectroscopy, revealing a maximum absorption edge at 650 nm corresponding to a band gap of 1.31 eV for Co3O4/Cg-C3N4 resulting in enhanced light absorption. Among the three fabricated electrodes, Co3O4/Cg-C3N4 exhibited a significantly lower overpotential of 30 mV and a minimum Tafel slope of 112 mV/dec This enhanced photoelectrochemical efficiency was found due to the established Z scheme heterojunction between Co3O4 and gC3N4. This heterojunction reduced the recombination of photogenerated electron-hole pairs and thus promoted charge separation by extending visible light absorption range chronoamperometric measurements confirmed the steady current flow over time under constant potential from the solar cell, and thus it provided the effective utilization of bifunctional Co3O4/g-C3N4 heterostructures for efficient solar-driven water splitting.

The construction of Z-scheme heterojunction ZnIn2S4@CuO with enhanced charge transfer capability and its mechanism study for the visible light degradation of tetracycline

In this study, copper oxide (CuO) was prepared by the microwave-assisted hydrothermal technique subsequently, CuO was grown in situ onto different rare metal compounds to prepare Z-scheme heterojunctions to improve the degradation efficiency of tetracycline (TC) in water environments. Various characterization proved the successful synthesis of all composite materials, and the formation of tight heterojunction interfaces, among which, the core–shell structure ZnIn2S4@CuO exhibited excellent photocatalytic degradation capability. Research results indicated that the degradation efficiency of ZnIn2S4@CuO for TC (50 mg/L) in the water environment reached 95.8 %, and the degradation rate is 2.41 times and 12.93 times that of CuO and ZnIn2S4 alone, respectively, the reason is because of the introduction of ZnIn2S4, Z-scheme heterojunction structures and internal electric field (IEF) is constructed and formed to extend the visible light response range of photocatalysts to improve electron-hole separation efficiency, and enhance charge transfer. In addition, ZnIn2S4@CuO-2 exhibited good stability and reproducibility, with no significant loss of activity after five cycles. Finally, the precise locations of free radical attack on TC were investigated by the combined use of high-resolution mass spectrometry (HR-MC) and frontier electron densities (FEDs), and a reasonable degradation pathway was provided. The results of this research provide a new and viable approach to overcome the limitations of conventional photocatalytic materials in terms of limited visible light absorption range and fast carrier recombination rates, which offers promising prospects for a wide range of applications in the field of wastewater purification.

Ultrafast photosensitized degradation of xanthates by using methylene blue as photosensitizer under simulated and natural solar light irradiation: Operational parameters, mechanism and toxicity evolution

Xanthates have attracted considerable attention due to their broad applications in mineral flotation process and unique natures including environmental persistence and toxicity. This study proposed an innovative approach for the efficient xanthates treatment from mineral processing wastewater. Methylene blue (MB) with good water solubility and strong light absorption in visible range was used as the photosensitizer to degrade potassium ethyl xanthate (PEX) under homogeneous conditions. MB, even at a very low concentration (0.5 mg/L), was found to rapidly remove PEX in only 10 min whether under simulated or natural solar light irradiation. Besides, the influences of various operational parameters, including photosensitizer dosage, PEX concentration, pH, light intensity, common ions, and water source on the photosensitized oxidation process was evaluated and analyzed. The possible degradation path of PEX was investigated depending on the intermediates detected by Liquid chromatography-mass spectrometry (LC-MS), and the photosensitized degradation mechanism was further speculated and validated by the radicals quenching experiments and electron paramagnetic resonance (EPR) spectroscopy. Furthermore, the toxicity of PEX was assessed against Bullfrog tadpole and Lemna minor, and it was found to be greatly reduced after treating with MB photosensitization. Overall, it is the first time that MB is proved to be an outstanding candidate for actual flotation wastewater treatment, providing a more efficient, economical and greener alternative to conventional methods.

Hierarchical LaTiO2N/Sn3O4 heterojunction with intimate interface contact for enhanced photocatalytic water splitting

LaTiO2N/Sn3O4 heterojunction with type-II band structure and hierarchical microstructure was constructed by decorating Sn3O4 nanoflowers and nanoflakes intimately on the surface of LaTiO2N nanosheets via a facile hydrothermal method. Compared with pure Sn3O4 and bare LaTiO2N, the photocatalytic H2 evolution activity for LaTiO2N/Sn3O4 heterostructure was boosted by ∼3 and ∼52 times, respectively, reaching 887 μmol·h−1·gcat−1. The mechanism for the elevated photocatalytic performance was systematically disclosed on the basis of comprehensive characterizations. Specifically, the introduced LaTiO2N extended the visible light absorption range to ∼600 nm, endowing Sn3O4 with more photogenerated charge carriers. Subsequently, the type-II band structure expedited the separation and migration of charge carriers, diminishing the internal recombination, thereby enhancing the photocatalytic activity. This work affords a new avenue for designing tin oxide-based and oxynitrides-based heterojunction.

Huge redshift of absorption edge in a novel Z-type Bi2Sn2O7/α-Bi2O3 junction for highly efficiently visible light degradation of norfloxacin and bisphenol AF

Heterojunction was mainly used to realize the separation of charge carrier in current studies, but it did not bring about any other effect. In this paper, Bi2Sn2O7 was introduced into α-Bi2O3 to construct a direct Z-type Bi2Sn2O7/α-Bi2O3 heterojunction. It not only accelerated the rapid separation of electrons and holes, but also induced a huge redshift of absorption edge to enlarge the visible light absorption range. Such result led into the optimal sample being able to degrade 95% of norfloxacin and 92% of bisphenol AF for 90 min of visible light irradiation. Under the same testing conditions, the removal efficiency of these two pollutants in the drinking water also attained 94% and 90% to demonstrate a good application. Moreover, the cycling test results indicated that the Bi2Sn2O7/α-Bi2O3 could be sustainably utilized. The electrons, holes, superoxide radical (•O2-) and hydroxyl radical (•OH) were the active substances in the process of degradation. The numbers of the Escherichia coli were 0.69×106 CFU/mL and 0.75×106 CFU/mL in the solutions after degradation to denote non-toxicity of the final products. Thus the Bi2Sn2O7/α-Bi2O3 composite could be applied in purification of various waste waters.