Z-scheme Heterostructure Research Articles

Synthesis of Z-scheme heterostructure FeWO<sub>4</sub>/rGO/g-C<sub>3</sub>N<sub>4</sub> as a visible-light photocatalyst for removal of organic pollutant

Photocatalysts have been effectively applied for water treatment. Narrow bandgap energy semiconductors show good photocatalytic performance at visible light. However, high recombination rate of the photogenerated electrons and holes leads to their low photocatalytic activity. Moreover, the conduction and valence band potentials of these materials are not suitable for the redox reactions with water and oxygen to generate HO• and •O2⁻ radicals, respectively. Therefore, the development of new photocatalyst systems to overcome these disadvantages is necessary. This study investigated the photocatalytic activity of FeWO4/rGO/g-C3N4 Z-scheme photocatalytic system via the degradation of Rhodamine B in water. The photocatalyst was synthesized by simple hydrothermal method and characterized by X-ray diffraction method (XRD), fluorescence spectroscopy (PL) and diffuse reflectance spectra (UV-vis). The results showed that after 150 minutes illumination, the Rhodamine B decomposition efficiency on FeWO4/g-C3N4 and FeWO4/rGO/g-C3N4 were 93.07 and 99.21%, respectively. These values were significantly higher than that of g-C3N4 under the same catalytic concentration of 0.1g/L. In the FeWO4/rGO/g-C3N4 heterostructure, rGO acted as electron mediator and transporter between two semiconductors, resulting in a lower recombination rate of photogenerated charges. As the results, the photocatalytic performance was enhanced.

Exploration of Photocatalytic Overall Water Splitting Mechanisms in the Z-Scheme SnS2/β-As Heterostructure

The Z-scheme heterostructure photocatalysts have irreplaceable advantages over other heterostructures due to their ability to separate the spatial carriers and retain strong redox ability. In this study, we explored the SnS2/β-As (β-arsenene) van der Waals heterostructure with Z-scheme properties and suitable band edge positions as a potential photocatalyst for overall water splitting. Under appropriate conditions, the hydrogen evolution reaction (HER) barrier is much closer to 0. Based on the oxidation product criteria, the SnS2/β-As heterostructure photocatalyst may generate multiple end products, including •OH, H2O2, and O2. Moreover, we screen the optimal and most possible reaction pathway OER-III under irradiation among three underlying oxygen evolution reaction (OER) mechanisms, in which the intermediate species HOOH* acts as a bridge for subsequent reactions. The solar-to-hydrogen conversion efficiency of the heterostructure can reach 17.18%. This work provides new insights into designing superior photocatalysts for overall water splitting and recognizing the OER mechanism.

Polyoxometalate anchored zinc oxide nanocomposite as a highly effective photocatalyst and bactericide for wastewater decontamination

Considering the remediation of water enviroments polluted by antibiotics and bacteria, it is critical to construct cost-effective, high-performance and environmentally friendly composites. In this work, a novel ZnO@PDA/Cu-POMs nanocomposite was first synthesized by post-grafting polyoxometalate (Cu-POMs) onto ZnO with the assistance of polydopamine (PDA) layer and then fully characterized. The nanocomposite exhibits high-efficiency photocatalytic degradation of tetracycline (TC, 90.75%) with good stability. Furthermore, it retains almost 80% removal efficiency in the presence of competing species. The excellent removal ability was derived from the Z-scheme heterostructure with compact interfacial contact and the synergistic effect between adsorption and photocatalysis. The photocatalytic mechanism and degradation pathway of TC also are elucidated. More importantly, the computational eco-toxicity analysis indicated that the degradation products had low biotoxicity compared to the original TC. It's worth noting that the ZnO@PDA/Cu-POMs nanocomposite shows extraordinary antibacterial activities against four gram-positive/negative bacteria (S. aureus, 99.88%, E. coli, 99.93%, B. cereus, 99.68%, P. aeruginosa, 99.60%) and two antibiotic-resistant bacteria (kanamycin-resistant E. coli, 92.27% and ampicillin-resistant E. coli, 88.93%) at low concentrations. Moreover, the antibacterial mechanism revealed that the synergistic action between ZnO@PDA and Cu-POMs damages the cellular membrane, increases oxidative stress levels, and leads to the death of bacteria. The current work provides a new perspective on the construction of multifunctional POM-based composites for environmental cleaning and water purification.

Visible light responsive MoS2/Ag@WO3/EG photoanode with highly stable Z-scheme induced circular electron motion pioneered by Exfoliated graphite for bisphenol a photoelectrodegradation

The alarming issue of endocrine disrupting chemicals increase in aquatic environment has heightened concerns about their potential impact on human health and ecosystem. Taking cognizance of this, the current investigation focused on fabrication of effective and efficient photoanode (MoS2/Ag@WO3/EG) from molybdenum disulphide/silver@tungsten trioxide (MoS2/Ag@WO3) photocatalyst and exfoliated graphite (EG) for the photoelectrocatalytic degradation of bisphenol A (BPA). The characterization results and Density Functional Theory (DFT) calculations together affirmed a strong interfacial contact and charge transfer direction at the interface of the materials for substantial promotion of charge separation and increased photoelectrocatalytic performance. The charge separation was further increased by EG’s “give-accept or redistribution” strategy of the charge at the interface that allowed circular motion of electrons in the formed Z-scheme heterostructure. The MoS2/Ag@WO3/EG photoanode exhibited the highest photoelectrocatalytic activity for BPA degradation with efficiency of 100% at optimum experimental conditions. The high degradation efficiency was attributed to uplifted visible light absorption emanating from EG surface plasmon resonance (SPR) contribution, formation of Z-scheme for efficient charge separation, and high stability of the photoanode, which possessed renewable surface. Moreover, scavenger experiments confirmed the participation of all the radicals (●O2– >●OH > h+) in BPA decomposition. Based on XPS, DFT, and radical experiments, the Z-scheme mechanism was proposed, and this work shed light on the production of highly effective house-made photoanode for photoelectrocatalytic processes, thus this can be a good fit in the industrial setup for degradation of other pollutants like microbials.

Ni-MOF-74-derived ZnIn2S4/P-Ni-MOF-74 Z-scheme heterojunctions for highly efficient photocatalytic hydrogen evolution under visible light irradiation

The construction of efficient Z-scheme heterojunctions is considered as a promising approach to improve the transfer and separation of photogenerated carries in the field of photocatalytic hydrogen evolution from water splitting. Herein, a novel ZnIn2S4/P-Ni-MOF-74 with Z-scheme heterostructure is successfully fabricated from rhombic P-Ni-MOF-74 derived from Ni-MOF-74 through phosphorization treatment and ZnIn2S4 flakes via a hydrothermal method. The Z-scheme ZnIn2S4/P-Ni-MOF-74 heterojunctions can provide abundant active centers, broaden the response range to visible light region, accelerate the transfer of interfacial charges, and suppress the recombination rate of photogenerated electron-hole pairs. As a result, ZnIn2S4/P-Ni-MOF-74 (20 wt% P-Ni-MOF-74) acquires a hydrogen production rate of 7865.31 μmol g−1 h−1, which is 4.46 times higher than that of ZnIn2S4. An apparent quantum yield is 7.84% at 420 nm wavelength. Overall, this work may provide a new pathway for the rational design of efficient Z-scheme heterojunctions with photocatalytic hydrogen evolution.

Tumor microenvironment-responsive artesunate loaded Z-scheme heterostructures for synergistic photo-chemodynamic therapy of hypoxic tumor

Tumor microenvironment (TME) with the particular features of severe hypoxia, insufficient endogenous H2O2, and overexpression of glutathione (GSH) markedly reduced the antitumor efficacy of monotherapy. Herein, a TME-responsive multifunctional nanoplatform (Bi2S3@Bi@PDA-HA/Art NRs) was presented for synergistic photothermal therapy (PTT), chemodynamic therapy (CDT), and photodynamic therapy (PDT) to achieve better therapeutic outcomes. The Z-scheme heterostructured bismuth sulfide@bismuth nanorods (Bi2S3@Bi NRs) guaranteed excellent photothermal performance of the nanoplatform. Moreover, its ability to produce O2 and reactive oxygen species (ROS) synchronously could relieve tumor hypoxia and improve PDT outcomes. The densely coated polydopamine/ammonium bicarbonate (PDA/ABC) and hyaluronic acid (HA) layers on the surface of the nanoplatform enhanced the cancer-targeting capacity and induced the acidic TME-triggered in situ “bomb-like” release of Art. The CDT treatment was achieved by activating the released Art through intracellular Fe2+ ions in an H2O2-independent manner. Furthermore, decreasing the glutathione peroxidase 4 (GPX4) levels by Art could also increase the PDT efficiency of Bi2S3@Bi NRs. Owing to the synergistic effect, this nanoplatform displayed improved antitumor efficacy with minimal toxicity both in vitro and in vivo. Our design sheds light on the application of phototherapy combined with the traditional Chinese medicine monomer-artesunate in treating the hypoxic tumor.

Photocatalytic Applications of ReS2-Based Heterostructures

ReS2-based heterostructures, which involve the coupling of a narrow band-gap semiconductor ReS2 with other wide band-gap semiconductors, have shown promising performance in energy conversion and environmental pollution protection in recent years. This review focuses on the preparation methods, encompassing hydrothermal, chemical vapor deposition, and exfoliation techniques, as well as achievements in correlated applications of ReS2-based heterostructures, including type-I, type-II heterostructures, and Z-scheme heterostructures for hydrogen evolution, reduction of CO2, and degradation of pollutants. We believe that this review provides an overview of the most recent advances to guide further research and development of ReS2-based heterostructures for photocatalysis.

Ferroelectric polarization and interface engineering coupling of Z-scheme ZnIn2S4/α-In2Se3 heterostructure for efficient photocatalytic water splitting

It is of great significance to design an efficient heterostructure for photocatalytic hydrogen production to solve the energy shortage and environmental crisis. In this letter, we investigate the structure, electron of interface, optical, charge transfer, and photocatalytic mechanism of three different ZnIn2S4/α-In2Se3 heterostructures by hybrid density functional calculation. It is interesting that the presence of an external electric field not only can change the bandgap but also can modulate the band alignment type. Among them, heterostructure A belongs to type II heterostructure, and heterostructure B and C belong to a Z-scheme heterostructure. Especially in heterostructure C, the electrons deposited on CBM of a ZnIn2S4 monolayer will play an important role in the hydrogen production process. Meanwhile, the small bandgap of ZnIn2S4/α-In2Se3 Z-scheme heterostructures enables it to obtain a wide light absorption range. Therefore, this study contributes to the design of a novel and potential Z-scheme heterostructure photocatalyst with broad application prospects in both electronic and optoelectronic fields.

Electron-buffer-mediated dual Z-scheme ZnSe/Ag2Se/AgBr heterojunction for efficient CO2 photocatalytic reduction

Design of photocatalysts with high-efficiency for sunlight utilization is one of the prerequisites for CO2 photoreduction. Besides, modulating a stable electron-donating environment to meet the energy barrier for CO2 reduction to CO is crucial. In this work, the ZnSe/Ag2Se/AgBr (ZAA) heterojunction was fabricated by growing the ZnSe on the AgBr surface accompanied by in-situ generation of Ag2Se between the two components by hydrothermal process. Results showed that the ZAA exhibited excellent light response ability over the full wavelength range. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) demonstrated that the charge transfer of the ZAA conformed to dual Z-scheme mechanism, with the Ag2Se acting as an electron transfer bridge, which in turn acted as an electron reservoir to accelerate electron transfer, facilitating carriers’ separation. The highest CO yield of 54.14 µmol/g/h was obtained from the optimal ZAA-2, which was 11.76 and 10.44 times of pure ZnSe and Ag2Se, respectively. This work demonstrated the feasibility of a dual Z-scheme heterostructure with full spectrum response for offering stable electron-donating environment and improving electron transfer for enhanced photocatalytic activity.

Encapsulation of tin oxide layers on gold nanoparticles decorated one-dimensional CdS nanoarrays for pure Z-scheme photoanodes towards solar hydrogen evolution

Despite their high potential for solar energy conversion into chemical fuels, most artificial all-solid-state Z-scheme photosystems have disordered structures and focus on power photocatalytic water splitting applications rather than photoelectrochemical (PEC) cells. Herein, an innovative pure Z-scheme heterostructure, CdS/Au/SnO2-S, composed of one-dimensional (1D) oriented CdS nanorods modified with SnO2-wrapped Au nanoparticles (NPs), was designed as a photoanode for highly efficient PEC hydrogen evolution. Systematic characterization confirms that the incorporated Au NPs not only act as the host platform to support the SnO2 layer growth but also play a key role as the electron mediator for strengthening the vectorial charge transfer from SnO2 to CdS. This reinforced Z-scheme charge transportation channel is favorable for suppressing the bulk charge recombination process, increasing the overall carrier density, and preserving the strong redox capability, ultimately resulting in a considerably improved photocurrent density and photo-to-current conversion efficiency with better corrosion resistance.

Constructing a Z-scheme Fe-MOF-based heterostructure for visible-light-driven oxidation of aromatic alcohol in ambient air

• Spindle-shaped MIL-53(Fe)-NH 2 @ZnIn 2 S 4 photocatalysts were facilely developed • A Z-scheme heterostructure is assuredly formed between ZnIn 2 S 4 and MIL-53-NH 2 • The photocatalytic BA conversion can be notably enhanced in ambient air • The benzaldehyde production rate can surpass most studies in air, O 2 or inert gas Photocatalytic oxidation of aromatic alcohol into aromatic aldehyde using O 2 has received huge attention, while the reaction that occurred in ambient air is rarely studied but follows the green-chemistry principles. Herein, spindle-shaped MIL-53(Fe)-NH 2 @ZnIn 2 S 4 photocatalysts with a Z-scheme heterostructure were facilely developed for photocatalytic oxidation of aromatic alcohol in air under visible light. The benzyl alcohol conversion can be notably enhanced to 73% over the optimal MIL-53-NH 2 @ZnIn 2 S 4 sample with a benzaldehyde production rate of 1825 μmol g –1 h –1 . However, in the O 2 atmosphere, the benzyl alcohol conversion is only 56%, indicating that O 2 is not required and has an adverse effect on the reaction. The hierarchical structure and Z-scheme heterojunction of MIL-53-NH 2 @ZnIn 2 S 4 impart an efficient separation and strong redox abilities of photo-induced electrons and holes, which are responsible for the impressive photocatalytic performance. This study could motivate the ingenious design of Z-scheme heterostructures for green organic conversion based on MOFs.

Construction of Z-scheme MnCo2O4/Sn3O4 heterostructured photoanodes with enhanced photoelectrocatalytic degradation of reactive brilliant blue KN-R

Rapid and efficient handling of the printing and dyeing wastewater benefits environmental conservation. Photoelectrocatalysis (PEC) technology is a novel method used to mineralize large molecules of non-degradable organic dye molecules in water completely into small molecules in recent years. By generating intermediate reactive species (e.g., superoxide radicals and hydroxyl radicals) during the processing, the products of PEC technology are cleaner and pollution-free, making it a desirable environment-friendly approach. In this work, a composite semiconductor material with Z-Scheme heterostructure was constructed as a photoanode to promote the generation of intermediate reactive radicals for the efficient degradation of organic dyestuff wastewater. A series of composite materials with Sn3O4 nanosheets decorated spinel-type MnCo2O4 nanorods were synthesized through a simple two-step hydrothermal process on the titanium metal substrate. The degradation reaction cell was assembled with these Ti/MnCo2O4-Sn3O4 photoanodes, and the PEC approach was used to decolorize the reactive brilliant blue KN-R. The synthesized photoelectrode exhibited a large electroactive region, low charge transfer resistance, high hydroxyl radical generation efficiency, and excellent PEC activity. The optimal composite photoanode presented 86.4 % reactive brilliant blue KN-R removal in 2 h and practical stability in 5 circulation tests. The mechanism during the PEC process was also analyzed and discussed on the basis of radical trapping experiments. In this work, MnCo2O4-Sn3O4 materials possessing Z-scheme heterojunction were constructed, providing insight into the techniques for catalytic purification of organic wastewater.

Construction of 2D/2D Bi12O17Cl2/Zn-HMT Z-scheme heterojunction for efficient photocatalytic tetracycline hydrochloride degradation and Cr(Ⅵ) reduction

Although photocatalysis technology is one of prospective method attributing to enormous potentials to environment issues, searching high-efficiency and stable photocatalysts remains the enormous challenges. In this work, we successfully constructed a novel 2D/2D Z-scheme heterostructure photocatalyst (BMT) in composed of Zn(Ⅱ)-hexamethylenetetramine (Zn-HMT) and Bi12O17Cl2 forming a 2D sheet-sheet stacking structure. The 2D/2D Z-scheme Bi12O17Cl2/Zn-HMT with intimate face-to-face contact inherits unique merits including large contact surface, abundant exposed active sites and shortened transmission paths of electrons, which would promote the separation of charges and the transmission efficiency of electrons in photocatalytic reaction. Attributing to these superiorities, the sample of 0.75-BMT with optimal proportion shows admirable photocatalytic performance for the photocatalytic tetracycline hydrochloride (TC-HCl, k1 =1.0 h−1) degradation and hexavalent chromium (Cr (Ⅵ), k2 = 0.43 h−1) reduction, which are about 2.6 and 4.3 times of pristine Zn-HMT, respectively. This work provides inventive inspiration for constructing a novel 2D/2D Z-scheme photocatalyst as the effect way to handle the environmental pollution issues.

Synthesis of GdFeO3/α-Fe2O3 heterostructure with enhanced photo-Fenton-like performance for organic pollutant degradation

The synergistic effects of photo-Fenton-like oxidation and heterostructure photocatalysis are highly beneficial for wastewater treatment. In this work, photo-Fenton-like GdFeO3 (GFO)/α-Fe2O3 catalysts with Z-scheme heterostructures were successfully fabricated via a facile ultrasonic method and then characterized using X-ray diffraction, transmission electron microscopy (TEM), field emission scanning electron microscopy, high-resolution TEM, ultraviolet–visible diffuse reflectance spectroscopy, X-ray photoelectron microscopy, photocurrent analysis, and electron impedance spectroscopy. The heterostructure with a GFO/Fe ratio of 3:7 showed the highest photocatalytic activity during degradation of organic pollutants, and adding small amounts of H2O2 increased its visible-light-driven catalytic activity by 9.5, 2.3, and 16.4 times that of rhodamine B, methylene blue, and tetracycline, respectively. The catalytic results were significantly improved due to the synergy of the Z-scheme heterostructure and photo-Fenton-like oxidation. The results indicate that an appropriate composition ratio can accelerate the conversion rate of surface ≡Fe3+ to ≡Fe2+ and promote the separation of electron–holes that can form more reaction active sites. Furthermore, a possible photocatalytic mechanism associated with the GFO/Fe composite was proposed using an electron spin resonance test and active-species trapping experiments. Overall, this work presents an important synthesis route for photo-Fenton-like catalysts that can degrade organic pollutants in wastewater.

Ag3PO4-anchored La2Ti2O7 nanorod as a Z-Scheme heterostructure composite with boosted photogenerated carrier separation and enhanced photocatalytic performance under natural sunlight

Developing wide spectra-responsive photocatalysts has attracted considerable attention in the photocatalytic technology to achieve excellent catalytic activity. Ag3PO4, with strong response to light spectra shorter than 530 nm, shows extremely outstanding photocatalytic oxidation ability. Unfortunately, the photocorrosion of Ag3PO4 is still the biggest obstacle to its application. Herein, the La2Ti2O7 nanorod was used to anchor Ag3PO4 nanoparticles in this study, and a novel Z-Scheme La2Ti2O7/Ag3PO4 heterostructure composite was constructed. Remarkably, the composite showed strong responsive to most of the spectra in natural sunlight. The Ag0 formed in-situ acted as the recombination center of photogenerated carriers, which promoted their efficient separation and contributed to the improved photocatalytic performance of the heterostructure. When the mass ratio of Ag3PO4 in the La2Ti2O7/Ag3PO4 catalyst was 50%, the degradation rate constant of Rhodamine B (RhB), methyl orange (MO), chloroquine phosphate (CQ), tetracycline (TC), and phenol under natural sunlight irradiation were 0.5923, 0.4463, 0.1399, 0.0493, and 0.0096 min−1, respectively. Furthermore, the photocorrosion of the composite was greatly inhibited, 76.49% of CQ and 83.96% of RhB were still degraded after four cycles. Besides, the holes and O2•− played a significant role in RhB degradation, and it included multiple mechanisms of deethylation, deamination, decarboxylation, and cleavage of ring-structures. Moreover, the treated solution can also show safety to the water receiving environment. Overall, the synthesized Z-Scheme La2Ti2O7/Ag3PO4 composite exhibited immense potential for removing various organic pollutants through photocatalytic technology under natural sunlight irradiation.

Boosted Light-Excited NO2 Detection Based on Hierarchical Z-Scheme MoS2/SnO2 Heterostructure Microspheres at Room Temperature

Light excitation has been developed as an economical way to realize room-temperature gas sensing recently. However, the high recombination rate of photogenerated carriers in semiconductor gas sensing materials leads to very limited carriers that can effectively take part in sensing reactions, which greatly restricts the further performance improvement of gas sensing under light excitation. Here, a hierarchical Z-scheme heterostructure microsphere of MoS2/SnO2 is designed and prepared. The heterostructure demonstrates an outstanding NO2 sensing performance at room temperature with the excitation of a low-power LED light (0.06 W), which exhibits an ultrahigh sensitivity of 264.2 to 10 ppm of NO2 along with acceptable response/recovery properties. The physical mechanism of NO2 sensing is analyzed. The results suggest that the construction of the Z-scheme heterostructure between MoS2 and SnO2 can greatly promote the separation of photogenerated carriers so that more photogenerated carriers can take part in the NO2 sensing reaction. Furthermore, the designing of a hierarchically porous structure can provide abundant active sites for gas sensing reactions. The work not only expands the development of Z-scheme heterostructures in gas sensing but also provides a strategy to promote the performance of light-excited gas sensors by designing a Z-scheme heterostructure with a hierarchically porous structure.

A Z-scheme photocatalysis for phenol eradication from water using peroxymonosulfate activation Ag/AgBr/SCN nanocomposite

BackgroundThe present work was mainly focused on construction of direct Z-scheme Ag/AgBr/SCN heterostructure and their photocatalytic ability to removal of phenol using synthesized photocatalysts. Ag/AgBr/SCN photocatalyst was prepared via facile deposition-precipitation method while bare g-C3N4 (GCN) and SCN (sulphur doped g-C3N4) were prepared via simple thermal-polycondensation method. MethodsThe Ag/AgBr/SCN Z-scheme heterostructure was fabricated by integration of 2D SCN with AgBr. Doping of sulphur in GCN structure has incremented the light absorption ability of GCN via reducing the energy gap to 2.64 eV from 2.7 eV. Different spectroscopic and analytical techniques have confirmed the successful formation of photocatalysts. Significant findingsThe addition of PMS during the photocatalytic experiment has enhanced the removal efficiency of photocatalysts due to more •OH and •SO4−radicals generation. It was observed from the results that PMS assisted Ag/AgBr/SCN photocatalytic material exhibited highest removal efficiency i.e. 99% compared to other bare photocatalysts within 80 min of visible-light exposure. Proposed mechanism validated the Z-scheme charge transfer route in Ag/AgBr/SCN in accord to apt band alignment in SCN and AgBr. However, Ag metal acted as an electron mediator to just transfer the electron from CB of SCN to CB of AgBr. The transference of electron from sulphur doped g-C3N4 to AgBr through Ag improved electron transportation. This ultimately enhanced charge separation rate and reduced the charge recombination rate in Ag/AgBr/SCN nanocomposite. The proposed mechanism also presented that •OH, SO4•− and •O2− radicals were the primary reactive species during Ag/AgBr/SCN/PMS assisted photocatalytic phenol degradation process (verified through scavenging tests). Finally, the recyclability experiment confirmed the stability and reusability of the prepared photocatalyst to 5 consecutive cycles. Consequently, this work presents a new perspective to fabricate greener, cheaper and proficient visible driven photocatalytic material for wastewater detoxification and environmental remediation.

0D/2D Z-schemed carbon nitride quantum dots/Bi2MoO6-x with enhanced carriers’ separation efficiency toward oxidation coupling of amines under ambient conditions

Organic synthesis driven by solar energy is receiving extensive attention due to its inherent merits like higher target product selectivity as well as milder reaction condition. While sluggish photoinduced charge carriers’ separation kinetic severely limited its utilization efficiency, leading to inefficient catalytic performance or energy-consuming reaction conditions. Assembling 0D/2D Z-schemed semiconductor nano-heterojunction would be a promising candidate for solving such problem. Herein, 0D/2D carbon nitride quantum dots (CNQDs)/Bi2MoO6-x (BMO-OD) was devised and synthesized by facile NaBH4-mediated hydrothermal method. The CNQDs/BMO-OD exhibited superior catalytic activity toward amines oxidation coupling under ambient conditions. Broad substrates suitability as well as excellent photochemical stability implies it would be a robust alternative amines oxidation coupling photocatalyst under mild conditions. The superior photocatalytic performance is attributed to expeditious photoinduced charge carriers’ separation and transfer of Z-schemed heterostructures and unique multipoint contact interface of 0D/2D. Scavenger experiments and ESR results demonstrates h+ and •O2– radicals play a major role in aerobic conditions while only h+ paly predominant role in anerobic conditions. The design and synthesis of 0D/2D CNQDs/BMO-OD Z-scheme heterostructures would be beneficial for boosting photoinduced carriers’ separation kinetic, thus promoting the photocatalytic oxidation coupling of amines under mild conditions.

Newly constructed Z-scheme Cu2ZnSnS4/BiOBr heterostructure for high-efficient photocatalytic applications

The structural design of semiconductor photocatalyst is a key factor to achieve high-efficient dye wastewater purification, in which the common drawbacks of weak redox kinetics, fast carrier recombination and insufficient optical response should be addressed, but still challenging. Herein, using two-step hydrothermal/solvothermal process, a direct Z-scheme heterostructured photocatalyst is newly constructed by coupling Cu2ZnSnS4 (CZTS) and BiOBr (BOB) nanosheets. Under the synergistic action of the narrow-gap photosensitive characteristics of CZTS and BOB’s intrinsic interlayered electric field, such Z-scheme CZTS/BOB can possess significantly enhanced photocatalytic activity for photo-degrading methyl orange, having the highest degradation efficiency of up to 99% within 40 min with the degradation rate of 0.0907 min−1, which is about 3.3 and 37.8 times higher compared with the bare BOB (0.0273 min−1) and CZTS (0.0024 min−1), respectively. Through detailed analysis, such direct Z-scheme heterostructures can facilitate to broaden visible light response, efficiently separate photogenerated carriers, inhibit recombination and enhance the redox capacity as well, thus contributing to the improved photocatalytic efficiency. This study might provide a new idea for the construction of BOB-based high efficiency catalysts.

Constructing direct Z-scheme heterojunctions of defective MoS2-v on carbon nitride nanotubes for high-performance hydrogen peroxide production and iron-free photo-Fenton-like reactions over a wide pH range

In this work, we first applied molybdenum disulfide with S vacancy (MoS2-v) /carbon nitride nanotube (TCN) composite (MoS2-v/TCN) to drive the iron-free photo-Fenton-like reaction. The well-designed band structure enables MoS2-v/TCN to construct direct Z-scheme heterostructures, realizing the rapid separation of photoinduced-e− and h+, and effectively improving the photocatalytic efficiency of MoS2-v/TCN. DFT calculation showed that Z-scheme heterojunction greatly reduced the energy barrier for generating *OOH and *HO2–, affording MoS2/TCN high performance and stability toward H2O2 generation (pure water: 254.8–269.9 μmol·g−1·h−1, 10 % isopropanol: 1879 μmol·g−1·h−1) over a wide pH range (3–9). The photoinduced-e− and Mo4+ on the surface of MoS2-v/TCN rapidly converted H2O2 in situ to strong oxidizing •OH, realizing the efficient degradation of organic pollutants and rapid inactivation of bacteria. This work provides a new approach to solving the technical bottlenecks in traditional Fenton oxidation via synthesizing multifunctional heterojunction for in situ H2O2 generation and activation.