Construction of hierarchical FeIn2S4/BiOBr S-scheme heterojunction with enhanced visible-light photocatalytic performance for antibiotics degradation

Constructing heterojunction provides a promising tactic to improve the photocatalytic efficiency of catalysts. In this paper, hierarchical FeIn₂S₄/BiOBr heterostructure photocatalysts were prepared by facile two step methods and applied to effectively remove ciprofloxacin (CIP) and tetracycline (TC) under visible light. Compared to single catalyst, FeIn₂S₄/BiOBr hybrids display significantly improved photocatalytic activity. Among the series, 6 wt% FeIn₂S₄/BiOBr shows the optimal photocatalytic performance, where the degradation efficiencies of TC and CIP are 3.15 and 2.88 times greater than pure BiOBr, respectively. Such an improvement could arise from the S-scheme heterojunctions and unique hierarchical structures, which brings stronger light absorption, higher photoexcited charge separation efficiency and superior redox ability. Furthermore, 6 wt% FeIn₂S₄/BiOBr composite exhibits excellent stability and reusability. Radical capture experiments and EPR analyses uncover that O₂^–, h⁺ and OH are primarily reactive substances during photocatalytic removal of TC. The products of TC were detected by LC-MS analyses and possible decomposition paths are proposed. Eventually, a possible photodegradation mechanism over FeIn₂S₄/BiOBr S-scheme heterojunction is proposed. These findings supply new perspective for the simple synthesis of S-scheme photocatalysts with promising applications in environment remediation.     

Exfoliated gC3N4 supported CdS nanorods as a S-scheme heterojunction photocatalyst for the degradation of various textile dyes

The quest to develop efficient photocatalysts in order to maintain a harmonious ecosystem by reducing water pollution from wastewater discharged from various industries is still in progress. Herein, we report a photocatalyst synthesized from exfoliated graphitic carbon nitride (gC₃N₄(ex)) and cadmium sulfide (CdS) which manifested excellent catalytic activity towards the degradation of various textile dyes in the presence of H₂O₂ (50CdS-50gC₃N₄(ex)). Under optimum reaction conditions, ～100 % degradation of some textile dyes such as Turq CL 5B, Red CL 5B, Yell CL 2R, Navy CLR, CB Sol Navy R, and Lanasol Black CE were observed in 10, 15, 30, 25, 30, and 15 min, respectively, when 50CdS-50gC₃N₄(ex) was used as the photocatalyst. This excellent photocatalytic efficiency of 50CdS-50gC₃N₄(ex) ascends from the establishment of synergy between nanorod-shaped CdS and exfoliated tubular-shaped gC₃N₄ due to their intimate concomitance in the nanocomposite. Moreover, the catalyst showed ～93 % catalytic efficiency as well as no change in the crystal structure or morphology after five catalytic cycles. Hence, this work puts forward a highly efficient environment-friendly, and reusable catalyst (50CdS-50gC₃N₄(ex)) which demonstrated its excellent potentiality to be utilized in the treatment of polluted effluents from textile industries under solar or blue LED irradiation.     

WS2/g-C3N4异质结光催化分解水制氢性能及机制

通过溶剂蒸发和二次高温煅烧石墨相碳化氮(g-C₃N₄)纳米片和WS₂纳米片混合物构建WS₂/g-C₃N₄异质结,该异质结保留g-C₃N₄和WS₂主体结构的同时,在界面处形成化学键,确保该异质结的化学稳定性和热稳定性。光催化分解水制氢实验表明,WS₂纳米片含量为3wt%时光催化制氢速率高达68.62 μmol/h,分别是g-C₃N₄纳米片和WS₂纳米片的2.53倍和15.29倍,表明异质结的构建可大幅提升g-C₃N₄的光催化性能,循环实验表明该异质结在5次循环实验后光催化性能没有明显下降,表明该异质结的稳定性较好。光电性能测试表明异质结的构建不仅提高激发电子的转移效率,同时抑制激发电子空穴的复合率,大幅提升激发电子的利用效率,致使光催化分解水制氢速率较g-C₃N₄纳米片和WS₂纳米片大幅提升。      

Controlling the charge carriers recombination kinetics on the g-C3N4-BiSI n-n heterojunction with efficient photocatalytic activity in N2 fixation and degradation of MB and phenol

The challenges like the photocatalytic reduction of N₂ and elimination of contaminants from the wastewater are accessible by low cost, stable, and visible-light-driven semiconductor-based photocatalysis. A novel g-C₃N₄/BiSI nanocomposite was synthesized by hydrothermal method and applied for the first time in photocatalytic nitrogen fixation and degradation of methylene blue dye and phenol. The physicochemical features of the photocatalysts were studied by XRD, XPS, FTIR, BET, DRS, FESEM, TEM, EDX mapping, PL, EIS, Mott-Schottky, and photocurrent techniques. Experimental results showed that the production of ammonia in the presence of g-C₃N₄/BiSI nanocomposite was 1280 μmol L^?1 g^?1, while this values for g-C₃N₄ and BiSI were 274 μmol g^?1 L^?1 and 126 μmol g^?1 L^?1, respectively. Moreover prepared nanocomposite exhibited a higher rate constant in the MB (537.5 × 10^?4 min^?1) and phenol (353 × 10^?4 min^?1) degradation compared with the counterparts. The charge separation efficiency obviously improved, which was ascribed to the charges migration between g-C₃N₄ and BiSI in an n-n heterojunction system. In addition, high specific surface area and strong visible light absorption were identified as other factors affecting photocatalytic performance. This unique heterojunction photocatalyst has wide application prospects in environmental treatment.     

Preparation of S- scheme heterojunction Bi28O32 (SO4)10/NiAl LDH for efficient photocatalytic degradation of tetracycline

At present, the construction of high-efficiency photocatalytic degradation system of antibiotic pollutants has become a research hotspot. In this paper, Bi₂₈O₃₂(SO₄)₁₀/NiAl LDH photocatalyst with three-dimensional spherical morphology was successfully prepared by hydrothermal method followed by calcination, thus applying to the degradation of tetracycline. The characterization and photochemical analysis of the resulted material were used to determine the type of formed heterojunction. Bi₂₈O₃₂(SO₄)₁₀ and NiAl LDH build a close contact interface. The matching band gap structure makes S-scheme heterojunction formed between the two single component. Benefited from this structure, the Bi₂₈O₃₂(SO₄)₁₀/NiAl LDH composite with the mass ratio of 1:1 exhibited 95% efficiency in degradation of tetracycline after irradiation for 120 min, and it is stable, reusable and universal. The apparent rate constant of TC degradation by heterojunction catalyst is greatly increased, which is 5.35 and 4.91 times that of Bi₂₈O₃₂(SO₄)₁₀ and NiAl LDH. Overall, this paper provides a way of thinking for the design of new bismuth based photocatalytic materials, and thus providing a reference for the rational design of S-scheme heterojunction.     

A novel Z-scheme Bi4O5I2/NiFe2O4 heterojunction photocatalyst with reliable recyclability for Rhodamine B degradation

Construction of heterojunction with reusability is one of the effective ways to avoid secondary pollution and strengthen photocatalysis. Herein, a magnetically recyclable Z-scheme Bi₄O₅I₂/NiFe₂O₄ heterojunction photocatalyst was successfully fabricated by a two-step hydrothermal method. Through adjusting the theoretical molar proportion of NiFe₂O₄ to Bi₄O₅I₂, it was verified that the optimal composite could decompose 98.5% Rhodamine B (RhB, 10 mg/L) within 60 min under simulative sunlight and 98.1% RhB within 80 min under visible light. According to the characterizations, the superior performance was mainly associated with the small band gap energy (2.44 eV) and efficient separation of photo-generated electrons and holes caused by the formation of heterojunction. Meanwhile, the enlarged specific area (27.6 m²/g) provided many adsorptive sites and active sites to improve the reaction further. Moreover, the trapping experiment indicated that the photodegradation involved O₂^–, OH and h⁺. After confirming the reliable activity, reusability and stability of the photocatalyst, an inferred mechanism was shown. In summary, the design of this magnetically recyclable Z-scheme Bi₄O₅I₂/NiFe₂O₄ heterojunction photocatalyst can become a new choice to purify wastewater.     

0D/2D Z-scheme heterojunctions of g-C3N4 quantum dots/ZnO nanosheets as a highly efficient visible-light photocatalyst

Constructing Z-scheme heterojunctions comprising of constituents with different dimensionality is an effective strategy to spatially separate electron and hole. To fully utilize the synergistic coupling effect of dimensionality, herein, we first immobilize g-C₃N₄ quantum dots (CNQDs) onto ZnO nanosheets with oxygen vacancies (OV-ZnO) to create a 0D/2D hybrid via a facile and cost-effective approach. The CNQDs/OV-ZnO heterojunctions display CNQDs content-dependent performance in visible-light photocatalytic activity. The optimal CNQDs/OV-ZnO heterojunction exhibits high photocatalytic activity for degradation of methyl blue and bisphenol A, where the kinetic constant is 11.4 and 32.5 fold of pure OV-ZnO, respectively. Photoluminescence, electrochemical impedance spectroscopy and photocurrent verify that the photogenerated electron-hole pairs in this 0D/2D Z-scheme heterojunction have been effectively separated. The enhanced photocatalytic activity could be attributed to the synergistic effect of efficient Z-scheme charge separation, highly dispersed 0D CNQDs, coordinating sites of 2D OV-ZnO nanosheets and the strong coupling between them. In addition, the 3D flower-like structure constructed by 2D nanosheets greatly inhibits the leaching and loss of the photocatalyst in the recycling process, and ensures the high recycling ability of CNQDs/OV-ZnO. This work paves the way toward designing novel visible-light 0D/2D photocatalysts in the application of solar energy.     

Facile synthesis of BiOCl/g-C3N4 heterojunction via in situ hydrolysis of Bi nanospheres: a high-efficiency visible-light-driven photocatalyst

Journal of Materials Science: Materials in Electronics - BiOCl/g-C3N4 (BC) heterojunctions were constructed successfully through a novel in situ hydrolysis method by taking metallic Bi nanospheres...     

Strongly Coupled g‐C3N4 Nanosheets‐Co3O4 Quantum Dots as 2D/0D Heterostructure Composite for Peroxymonosulfate Activation

The development of effective approaches for the preparation of 0D quantum dots (QDs)/2D nanosheets (NSs) heterostructures, which have been proven to be favorable for heterogeneous catalysis, is highly desirable but remains a great challenge. Herein, 0D metal oxide nanocrystals–2D ultrathin g‐C₃N₄ nanosheets (Co₃O₄/CNNS) heterostructures are synthesized via a facile chemical reaction, followed by annealing in air. Ultrafine Co₃O₄ QDs (≈2.2–3.2 nm) are uniformly and tightly attached on the surface of g‐C₃N₄ nanosheets. Detailed characterization reveals that the specially designed unique 0D/2D structure is critical to the high photocatalytic performance for the degradation of tetracycline (TC) via peroxymonosulfate (PMS) activation. The optimal catalyst, namely, Co₃O₄/CNNS‐1100, exhibits excellent performance and ≈98.7% TC can be degraded under visible light irradiation. Moreover, TC degradation is almost completely insusceptible to several real water samples. Meanwhile, other dye pollutants can also be efficiently degraded by the Co₃O₄/CNNS‐1100/PMS/vis system. The quenching tests display that that the h⁺, ?OH, O₂^??, and SO₄^?? are responsible for TC removal. The improved photocatalytic performance can be attributed to the synergistic effect of the photocatalytic‐ and chemical‐processes in the PMS activation. This work gives an insight into the development of multifunctional 0D/2D nanocomposites for further potential applications which are not limited to environmental purification.     

Metal‐Free 2D/2D Phosphorene/g‐C3N4 Van der Waals Heterojunction for Highly Enhanced Visible‐Light Photocatalytic H2 Production

The generation of green hydrogen (H₂) energy using sunlight is of great significance to solve the worldwide energy and environmental issues. Particularly, photocatalytic H₂ production is a highly promising strategy for solar‐to‐H₂ conversion. Recently, various heterostructured photocatalysts with high efficiency and good stability have been fabricated. Among them, 2D/2D van der Waals (VDW) heterojunctions have received tremendous attention, since this architecture can promote the interfacial charge separation and transfer and provide massive reactive centers. On the other hand, currently, most photocatalysts are composed of metal elements with high cost, limited reserves, and hazardous environmental impact. Hence, the development of metal‐free photocatalysts is desirable. Here, a novel 2D/2D VDW heterostructure of metal‐free phosphorene/graphitic carbon nitride (g‐C₃N₄) is fabricated. The phosphorene/g‐C₃N₄ nanocomposite shows an enhanced visible‐light photocatalytic H₂ production activity of 571 µmol h^?1 g^?1 in 18 v% lactic acid aqueous solution. This improved performance arises from the intimate electronic coupling at the 2D/2D interface, corroborated by the advanced characterizations techniques, e.g., synchrotron‐based X‐ray absorption near‐edge structure, and theoretical calculations. This work not only reports a new metal‐free phosphorene/g‐C₃N₄ photocatalyst but also sheds lights on the design and fabrication of 2D/2D VDW heterojunction for applications in catalysis, electronics, and optoelectronics.     

An excellent Z-scheme Ag2MoO4/Bi4Ti3O12 heterojunction photocatalyst: Construction strategy and application in environmental purification

Herein we have designed an excellent type of Z-scheme Ag₂MoO₄/Bi₄Ti₃O₁₂ (AMO/BTO) heterojunction photocatalysts by immobilizing AMO particles onto rod-like BTO hierarchical architectures. The formation of Z-scheme AMO/BTO heterostructures was verified by various characterization techniques including XRD, UV–vis DR spectroscopy, SEM, TEM, XPS and FTIR spectroscopy. PL spectroscopy, photocurrent response and EIS analyses suggest that the creation of AMO/BTO heterojunctions is conducive to the efficient separation of photoexcited electron-hole pairs. The photocatalytic performances of the AMO/BTO composites were investigated by simulated-sunlight driving photodegradation of methylene blue (MB), tetrabromobisphenol A (TBBPA), tetracycline hydrochloride (TC), phenol and methyl orange (MO)/rhodamine B (RhB)/MB mixture solutions. It is demonstrated that the AMO/BTO heterojunction photocatalysts are endowed with excellent photodegradation performances much higher than that of bare AMO and BTO. For example, the photodegradation rate of MB by using 30 wt%AMO/BTO — confirmed to be the optimal composite sample — is about 17.0 and 14.7 times as high as that by using bare BTO and AMO, respectively. A Z-scheme electron transfer mechanism was proposed to elucidate the enhanced photodegradation performances of the AMO/BTO heterojunction photocatalysts.     

Preparation of a 3D flower-like spherical structure g-C3N4/CuBi2O4/Bi2MoO6 photocatalyst for efficient removal of antibiotics under visible light

For the remediation of antibiotic-contaminated water bodies, this study synthesized g-C₃N₄/CuBi₂O₄/Bi₂MoO₆ 3D flower-like spherical photocatalysts by a solvothermal method. The tetracycline antibiotics were used as the target pollutants and degraded under visible light to evaluate the photocatalytic performance of the prepared photocatalysts. Notably, the g-C₃N₄/CuBi₂O₄/Bi₂MoO₆ photocatalyst achieved 84.6 % and 91.6 % for the degradation of tetracycline hydrochloride and chlortetracycline (100 mL, 20 mg/L), respectively, within 2 h under visible light irradiation. Furthermore, we found that the composites showed very low degradation rates for dye-based contaminants, but still exhibited excellent photocatalytic activity for antibiotics in a mixed contaminant system of dyes and antibiotics. And the intermediate was detected by gas chromatography-mass spectrometry (GC–MS), suggesting a possible photo-degradation pathway for tetracycline. Finally, biochemical experiments were carried out to further illustrate the effective degradation of antibiotics in water after photocatalytic degradation by observing and comparing the growth of mung bean seeds.     

Faster Electron Injection and More Active Sites for Efficient Photocatalytic H2 Evolution in g‐C3N4/MoS2 Hybrid

Herein, the structural effect of MoS₂ as a cocatalyst of photocatalytic H₂ generation activity of g‐C₃N₄ under visible light irradiation is studied. By using single‐particle photoluminescence (PL) and femtosecond time‐resolved transient absorption spectroscopies, charge transfer kinetics between g‐C₃N₄ and two kinds of nanostructured MoS₂ (nanodot and monolayer) are systematically investigated. Single‐particle PL results show the emission of g‐C₃N₄ is quenched by MoS₂ nanodots more effectively than MoS₂ monolayers. Electron injection rate and efficiency of g‐C₃N₄/MoS₂‐nanodot hybrid are calculated to be 5.96 × 10⁹ s^?1 and 73.3%, respectively, from transient absorption spectral measurement, which are 4.8 times faster and 2.0 times higher than those of g‐C₃N₄/MoS₂‐monolayer hybrid. Stronger intimate junction between MoS₂ nanodots and g‐C₃N₄ is suggested to be responsible for faster and more efficient electron injection. In addition, more unsaturated terminal sulfur atoms can serve as the active site in MoS₂ nanodot compared with MoS₂ monolayer. Therefore, g‐C₃N₄/MoS₂ nanodot exhibits a 7.9 times higher photocatalytic activity for H₂ evolution (660 µmol g?¹ h^?1) than g‐C₃N₄/MoS₂ monolayer (83.8 µmol g^?1 h^?1). This work provides deep insight into charge transfer between g‐C₃N₄ and nanostructured MoS₂ cocatalysts, which can open a new avenue for more rationally designing MoS₂‐based catalysts for H₂ evolution.     

Mn2O3 decorated graphene nanosheet: An advanced material for the photocatalytic degradation of organic dyes

A one step sonochemical route has been developed to prepare graphene–Mn₂O₃ nanocomposite with uniform distribution of Mn₂O₃ nanoparticles throughout the surface of graphene nanosheet. Growth of such nanoparticles over this two dimensional carbon network is simply accelerated by the simultaneous reduction of potassium permanganate along with graphene oxide, in which metal ions are first anchored through binding with oxy-functional groups of graphene oxide and finally reduced by hydrazine. The final product ensure a new platform for the photodegradation of organic dyes, as it can store electrons and circulate them towards dye molecules through the formation of hydroxyl radical under the exposure of UV-light. Almost 80% photocatalytic degradation of eosin, methylene blue and rhodamine B have been observed within few minutes, which has not been obtained by using bare manganese oxide itself.     

Ag2O modified magnetic BaFe12O19/C3N4 photocatalysts with enhanced antibiotic removal: Photocatalytic mechanism and toxicity evaluation

Novel Ag₂O-BaFe₁₂O₁₉/C₃N₄ composites were prepared via a grind, solvothermal and deposition–precipitation methods. The physicochemical properties of the samples were tested by FT-IR, XRD, SEM, TEM, XPS, DRS, ESR, VSM, photocurrent test, and electrochemical impedance spectra test, respectively. The characterization manifested that Ag₂O was firmly anchored to the BaFe₁₂O₁₉/C₃N₄ to form heterogeneous hybrid. Most importantly, the formation of Ag₂O-BaFe₁₂O₁₉/C₃N₄ effectively promoted the charge transfer, eventually enhancing the photocatalytic performance. Meanwhile, the activity of the photocatalysts were assessed by photocatalytic removal of tetracycline (TC) under visible light irradiation. The results showed that Ag₂O-BaFe₁₂O₁₉/C₃N₄ photocatalyst has better photocatalytic activities than the pure component. The degradation rate reaches 80 % after 15 min, which is nearly 1.56 times higher than that of pure g-C₃N₄. The effects of Ag₂O content, photocatalyst dosage, pH value on TC degradation performances were studied in detail, respectively. The experimental results verified that pH value exhibited significant effects on TC degradation. The TC degradation rate was highest only when the initial solution pH = 7. This indicates that the photocatalyst also has high activity in neutral environment, and no additional pH adjustment is required. The results of plant growth test (mung bean seeds) showed that the degradation intermediates showed lower toxicity. Based on experiments and characterization, the possible carrier migration and photocatalytic degradation mechanism were proposed.     

High performance magnetically recoverable g-C3N4/Fe3O4/Ag/Ag2SO3 plasmonic photocatalyst for enhanced photocatalytic degradation of water pollutants

The g-C₃N₄/Fe₃O₄/Ag/Ag₂SO₃ nanocomposites have been successfully fabricated by facile refluxing method. The as-obtained products were characterized by XRD, EDX, SEM, TEM, UV–vis DRS, FT–IR, TGA, PL, and VSM techniques. The results suggest that the Ag/Ag₂SO₃ nanoparticles have anchored on the surface of g-C₃N₄/Fe₃O₄ nanocomposite, showing strong absorption in the visible region. The evaluation of photocatalytic activity indicates that for the g-C₃N₄/Fe₃O₄/Ag/Ag₂SO₃ (40%) nanocomposite, the degradation rate constant was 188 × 10^?4 min^?1 for rhodamine B, exceeding those of the g-C₃N₄ (16.0 × 10^?4 min^?1) and g-C₃N₄/Fe₃O₄ (20.2 × 10^?4 min^?1) by factors of 11.7 and 9.3, respectively. The results showed that the nanocomposite prepared by refluxing for 120 min has the superior photocatalytic activity and its activity decreased with rising the calcination temperature. The trapping experiments confirmed that superoxide ion radical was the main active species in the photocatalytic degradation process. Also, it was demonstrated that the magnetic photocatalyst has considerable activity in degradation of one more dye pollutant. Finally, the reusability of the photocatalyst was evaluated by five consecutive catalytic runs. This work may open up new insights into the utilization of magnetically separable nanocomposites and provide new opportunities for facile fabrication of g-C₃N₄-based plasmonic photocatalysts.     

Ultrasmall Fe3O4 Nanoparticle/MoS2 Nanosheet Composites with Superior Performances for Lithium Ion Batteries

A novel composite consisting of graphene‐like MoS₂ nanosheets and ultrasmall Fe₃O₄ nanoparticles (≈3.5 nm) is synthesized as an anode for lithium ion battery application. In such composite anode, MoS₂ nanosheets provide flexible substrates for the nanoparticle decoration, accommodating the volume changes of Fe₃O₄ during cycling process; while Fe₃O₄ nanoparticles primarily act as spacers to stabilize the composite structure, making the active surfaces of MoS₂ nanosheets accessible for electrolyte penetration during charge/discharge processes. Owing to the high reversible capacity provided by the MoS₂ nanosheets and the superior high rate performance offered by ultrasmall Fe₃O₄ nanoparticles, superior cyclic and rate performances are achieved by Fe₃O₄/MoS₂ anode during the subsequent electrochemical tests, delivering 1033 and 224 mAh g^?1 at current densities of 2000 and 10 000 mA g^?1, respectively.     

2D Electron Gas and Oxygen Vacancy Induced High Oxygen Evolution Performances for Advanced Co3O4/CeO2 Nanohybrids

The rational design of atomic‐scale interfaces in multiphase nanohybrids is an alluring and challenging approach to develop advanced electrocatalysts. Herein, through the selection of two different metal oxides with particular intrinsic features, advanced Co₃O₄/CeO₂ nanohybrids (NHs) with CeO₂ nanocubes anchored on Co₃O₄ nanosheets are developed, which show not only high oxygen vacancy concentration but also remarkable 2D electron gas (2DEG) behavior with ≈0.79 ± 0.1 excess e^?/u.c. on the Ce³⁺ sites at the Co₃O₄–CeO₂ interface. Such a 2DEG transport channel leads to a high carrier density of 3.8 × 10¹⁴ cm^?2 and good conductivity. Consequently, the Co₃O₄/CeO₂ NHs demonstrate dramatically enhanced oxygen evolution reaction (OER) performances with a low overpotential of 270 mV at 10 mA cm^?2 and a high turnover frequency of 0.25 s^?1 when compared to those of pure Co₃O₄ and CeO₂ counterparts, outperforming commercial IrO₂ and some recently reported representative OER catalysts. These results demonstrate the validity of tailoring the electrocatalytic properties of metal oxides by 2DEG engineering, offering a step forward in the design of advanced hybrid nanostructures.