Z-scheme Heterostructure Research Articles

Incorporating ReS2 Nanosheet into ZnIn2S4 Nanoflower as Synergistic Z-Scheme Photocatalyst for Highly Effective and Stable Visible-Light-Driven Photocatalytic Hydrogen Evolution and Degradation.

Inspired by natural photosynthesis, the visible-light-driven Z-scheme system is very effective and promising for boosting photocatalytic hydrogen production and pollutant degradation. Here, a synergistic Z-scheme photocatalyst is constructed by coupling ReS2 nanosheet and ZnIn2S4 nanoflower and the experimental evidence for this direct Z-scheme heterostructure is provided by X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and electron paramagnetic resonance. Consequently, such a unique nanostructure makes this Z-scheme heterostructure exhibit 23.7 times higher photocatalytic hydrogen production than that of ZnIn2S4 nanoflower. Moreover, the ZnIn2S4/ReS2 photocatalyst is also very stable for photocatalytic hydrogen evolution, almost without activity decay even storing for two weeks. Besides, this Z-scheme heterostructure also exhibits superior photocatalytic degradation rates of methylene blue (1.7 × 10-2 min-1) and mitoxantrone (4.2 × 10-3 min-1) than that of ZnIn2S4 photocatalyst. The ultraviolet-visible absorption spectra, transient photocurrent spectra, open-circuit potential measurement, and electrochemical impedance spectroscopy reveal that the superior photocatalytic performance of ZnIn2S4/ReS2 heterostructure is mostly attributed to its broad and strong visible-light absorption, effective separation of charge carrier, and improved redox ability. This work provides a promising nanostructure design of a visible-light-driven Z-scheme heterostructure to simultaneously promote photocatalytic reduction and oxidation activity.

Developing Z-scheme Bi2MoO6@α-MnO2 beaded core-shell heterostructure in photoelectrocatalytic treatment of organic wastewater

Photoelectrocatalysis (PEC) oxidation technology with the combination of electrocatalysis and photocatalysis is an ideal candidate for treatment of dyeing wastewater containing multifarious intractable organic compounds with high chroma. Constructing high-quality heterojunction photoelectrodes can effectively suppress the recombination of photo-generated carriers, thereby achieving efficient removal of pollution. Herein, a beaded Bi2MoO6@α-MnO2 core-shell architecture with tunable hetero-interface was prepared by simple hydrothermal-solvothermal process. The as-synthesized Bi2MoO6@α-MnO2 had larger electrochemically active surface area, smaller charge transfer resistance and negative flat band potential, and higher separation efficiency of e−/h+ pairs than pure α-MnO2 or Bi2MoO6. It is noteworthy that the as-synthesized Bi2MoO6@α-MnO2 showed Z-scheme heterostructure as demonstrated by the free radical quenching experiments. The optimized Bi2MoO6@α-MnO2-2.5 exhibited the highest degradation rate of 88.64% in 120 min for reactive brilliant blue (KN-R) and accelerated stability with long-term(∼10000s) at the current density of 50 mA cm−2 in 1.0 mol L−1 H2SO4 solution. This study provides valuable insights into the straightforward preparation of heterogeneous electrodes, offering a promising approach for the treatment of wastewater in various industrial applications.

Host-Guest Interaction Mediated Perovskite@Metal-Organic Framework Z-Scheme Heterojunction Enabled Paper-Based Photoelectrochemical Sensing.

Exploring the high-performance photoelectronic properties of perovskite quantum dots (QDs) is desirable for paper-based photoelectrochemical (PEC) sensing;however, challenges remain in improving their stability and fundamental performance. Herein, a novel Z-scheme heterostructure with host-guest interaction by the confinement of CH3NH3PbBr3 QDs within Cu3(BTC)2 metal-organic framework (MOF) crystal (MAPbBr3@Cu3(BTC)2) is successfully constructed on the paper-based PEC device for ultrasensitive detection of Ochratoxin A (OTA), with the assistance of the exciton-plasmon interaction (EPI) effect. The host-guest interaction is estabilished by encapsulating MAPbBr3 QDs as guests within Cu3(BTC)2 MOF as a host, which prevents MAPbBr3 QDs from being damaged in the polar system, offering access to long-term stability with high-performance PEC properties. Benefiting from the precise alignment of energy levels, the photogenerated charge carriers can migrate according to the Z-scheme charge-transfer pathway under the driving force of the internal electric field, achieving a high photoelectric conversion efficiency. Upon OTA recognition, the EPI effect is activated to modulate the exciton response in MAPbBr3 QDs by accelerating radiative decay, finally achieving sensitive OTA sensing with a detection limit of 0.017 pg mL-1. We believe this work renders new insight into designing host-guest Z-scheme heterojunctions in constructing the paper-based PEC sensing platforms for environmental monitoring.

Construction of highly porous Z-scheme CuSe2/ZnSe heterostructure to achieve efficient CO2 photoreduction activity

The use of photocatalysts to convert CO2 into useful fuels is an important field of interest. Constructing morphology-controlled Z-scheme heterostructure is an effective method for improving photocatalyst surface charge localization. This can be achieved through facile and effective methods of loading appropriate co-catalysts to improve photocatalytic activity. In this study, a highly porous surface-morphology-controlled Z-scheme CuSe2/ZnSe heterostructure was successfully constructed. Among all composition ratios, 0.6 mmol CuSe2/ZnSe showed superior photocatalytic performance and stability, with the highest CO and CH4 yields of 616 and 351 µmolg−1, respectively, and a selectivity of 89 %. Both the effective interfacial charge transfer and the highly porous structure of the material influenced the separation and transfer of photogenerated charge carriers. This study is expected to provide useful information for engineering heterojunctions with morphology-controlled photocatalysts and investigating their charge transfer dynamics.

Enhanced light absorption and charge carrier’s separation in g-C3N4-based double Z-scheme heterostructure photocatalyst for efficient degradation of navy-blue dye

ABSTRACT Effective wastewater treatment is essential due to the dye environmental threats. Photocatalysis offers an eco-friendly dye degradation solution. Herein, we report a double Z-scheme photocatalyst, i.e. LaFeO3/Boron-doped g-C3N4/Fe2O3 (LFO/B-CN/FO), fabricated via a hydrothermal method. The formation of this ternary system is supported by structural, surface, and morphological analyses. Differential scanning calorimetry and thermal gravimetric analysis demonstrated the crystallization behavior of the composite. Because of synergetic effects in the ternary composite and boron doping, the optical band gap energy is reduced to 1.6 eV. Under visible light irradiation, the LFO/B-CN/FO nanocomposite degraded navy-blue dye by 98% in 130 min at neutral pH, surpassing CN, B-CN, and binary composites of B-CN with LFO and FO. The degradation process was rationalized using pseudo-first- and pseudo-second-order kinetic models, which confirmed high catalytic efficiency. The double Z-scheme heterojunction enhanced light absorption, charge separation, and carrier lifetime, hence improving the photocatalytic activity. Overall, the as-fabricated LFO/B-CN/FO ternary composite outperformed reference catalysts in terms of chemical reactivity, optical characteristics, and electrical performance. This work opens up a new route for the design and fabrication of double Z-scheme ternary composite photocatalysts for potential wastewater treatment and renewable energy applications.

Construction of broad-spectrum photocatalyst films through interface engineering: Orchestrating Bi nanoparticles in TiO2/BiVO4 Z-scheme heterojunctions

We successfully synthesized three-layered photocatalysts by modifying Bi nanoparticles on TiO2/BiVO4 bilayer composite films through a sol-gel process and sputtering. When exposed to ambient air, the surface of the prepared Bi nanoparticles oxidizes to form an amorphous ultra-thin Bi2O3 out layer. Under light exposure, this layer is reduced to metallic Bi, thanks to the band alignment between the Bi nanoparticles and TiO2/BiVO4 Z-scheme composite. The addition of Bi nanoparticles in the composite films improves visible-light absorption by the surface plasmon resonance (SPR), which contributes to the hot electron and enhances the photocatalytic characteristics. By constructing effective TiO2/BiVO4 Z-scheme heterostructures to facilitate photoinduced electron-hole pair separation and prevent recombination, Bi nanoparticles can efficiently capture photons and enhance the photocatalytic efficiency of semiconductors through the SPR effect. Optimizing the content of Bi nanoparticles decorated on the TiO2/BiVO4 Z-scheme composite film is a promising approach for designing a highly efficient photocatalyst, as evidenced by the performance of photoelectrochemical properties and RhB photodegradation ability.

Interface-engineering derived WS2/S-g-C3N4 nanosheet Z-scheme heterostructures towards enhanced photocatalytic redox and H2O2 generation

The growth of WS2 on S-doped graphic carbon nitrides (g-C3N4) was controlled to utilize horizontal implanting and get fine interfacial characteristic. Superior thin S-doped g-C3N4 nanosheets were fabricated via a two-step thermal polymerization at high temperature. Subsequent solvothermal procedure was used to create WS2/S-g-C3N4 (WS2/SCN) photocatalytic heterojunctions with optimized component ratios, in which doped S components in g-C3N4 play an important role for the horizontal growth and homogeneous distribution of WS2 nanosheets. Z-scheme charge transfer mechanism was proposed according to various characterizations. Photocatalytic rhodamine B (Rh B) degradation test indicated that WS2/SCN 15 % (sample WS2/SCN-3) revealed the best performance, in which Rh B of 92.8 % was photocatalytic oxidated with 20 min. Photocatalytic hydrogen generation experiments indicated that sample WS2/SCN-3 exhibited a H2 generation rate of 1380 μmol·g−1∙h−1, which was 3.7 times of that of S-g-C3N4 nanosheets. These WS2/S-g-C3N4 heterojunctions also exhibited excellent performance for photocatalytic H2O2 evolution. Sample WS2/SCN-3 exhibited a H2O2 generation rate of 5216 μmol·g−1·h−1 which was 6.4 times that of S-g-C3N4 sample. This excellent photocatalytic activity is scribed to WS2/S-g-C3N4 layered heterojunctions with well-developed interface characteristic. The result supplied an efficient approach for the preparation of photocatalysts.

Investigation on thermodynamic stability and electronic structure properties of Bi2CrO6 (0 0 1) surface using density functional theory

A density functional theory (DFT)-based thermodynamic approach was applied to investigate the stability and analyze the surface electronic structures of potential termination structures for the Bismuth chromate (Bi2CrO6) (001) surface. Five Bi2CrO6 (001) surface terminations can be stabilized under certain thermodynamic equilibrium conditions, according to the constructed Bi-Cr-O surface phase diagrams, which are based on calculated surface Gibbs free energies. Analysis of the surface electronic structure shows that O-Bi surface termination has high potential for photocatalytic applications. Additionally, the work functions exhibit substantial differences across various Bi2CrO6 surface terminations, implying that by selecting the thermodynamically more stable surface termination under suitable conditions, the performance of the direct Z-scheme heterostructure based on Bi2CrO6 can be optimized. These findings offer a valuable approach for subsequent experimental research on Bi2CrO6-based photocatalysts and facilitate the investigation of the intrinsic characteristics of Bi2CrO6 surfaces.

Facile construction of SPR effect assisted Bi2O2CO3/Bi/BiOCl Z-scheme heterostructure for robust photocatalytic decontamination of RhB

A ternary Bi2O2CO3/Bi/BiOCl Z-scheme heterostructure with an ordered flower-like structure was synthesized by controlling KCl content using a facile solvothermal technique, and the photodegradation performance of RhB was investigated in detail. The photocatalytic results suggested that the Bi2O2CO3/Bi/BiOCl manifested an attractive photodegradation rate with 99.20 % of removal efficiency within 20 min of irrigation. The main reason was credited to the SPR effect of metallic Bi and the construction of Z-scheme heterojunction, endowing enhanced adsorption ability of visible light, long lifetime of charge carriers, and fast interfacial electron flow. Furthermore, the degradation pathways towards RhB were also elaborated via LC–MS. A possible photocatalytic mechanism was explored by combining the radicals quench experiments, ESR tests with energy band structures. The study will supply a potential candidate for the remediation of natural RhB wastewater.

Highly efficient photocatalytic performance of Z-scheme BTe/HfS2 heterostructure for H2O splitting

Constructing van der Waals (vdW) heterostructures is one of the effective strategies for developing highly efficient photocatalysts. In this study, we have designed a novel BTe/HfS2 heterostructure and systematically investigated its electronic properties and photocatalytic performance using first-principles calculations. The dynamic stability and thermodynamic stability of the heterostructure are verified through phonon spectrum simulations and ab initio molecular dynamics (AIMD) simulations, respectively, enhancing the likelihood of experimental synthesis. The bandgap of the BTe/HfS2 heterostructure is 0.12 eV, and the band edge positions satisfy the overall water splitting requirements for photocatalysts. The charge density difference, work function, Bader charge, and band alignment all confirm that the BTe/HfS2 heterostructure is a typical direct Z-scheme heterostructure, effectively facilitating the separation of photogenerated charge carriers and exhibiting strong redox capability. The solar-to-hydrogen (STH) efficiency of the BTe/HfS2 heterostructure reaches as high as 17.32 %. Moreover, the heterostructure exhibits strong light absorption capability, reaching a magnitude of 105. The carrier mobility of the BTe/HfS2 heterostructure surpasses that of two individual monolayer materials, with the hole mobility in the x-direction reaching an impressive 28357.15 cm2s-1V-1. Simultaneously, the Gibbs free energy indicates that the BTe/HfS2 heterostructure can undergo the hydrogen evolution reaction (HER) with only 0.19 eV of external potential at pH = 0. Moreover, at pH = 7, it can spontaneously convert H2O into O2. Therefore, the newly designed BTe/HfS2 heterostructure offers a new direction for practical applications of photocatalysts.

Oxygen vacancies and Y-O-Ag bonds in the Z-scheme heterojunction cooperate to promote photodegradation of organic pollutants

Y2O3 is a cost-effective and environmentally friendly wide-band gap photocatalyst with extensive application potential. However, its limited ability to be excited by visible light restricts its practical uses. In this study, we coupled the narrow bandgap semiconductor AgI with Y2O3 to form a Z-scheme heterostructure, significantly promoting its photocatalytic degradation activity. Characterization and experimental results demonstrated the formation of Y-O-Ag bonds through coupling with AgI, leading to an increase in oxygen vacancies in Y2O3, which promotes the chemisorption of H2O and O2. The Y-O-Ag bond introduction promotes electron transfer, improves hole utilization, and boosts energy transfer efficiency, thus promoting the efficient generation of ·OH and 1O2. The photocatalytic degradation rates of RhB and o-nitrophenol by 7.5% AgI/Y2O3 were 26.5 and 4 times higher than those of pure Y2O3, respectively. This study provides theoretical support for the Z-scheme heterojunction to improve photocatalytic activity and offers efficient solutions and practical design ideas for sewage purification.

FeOCl/MOF-derived In2S3 photocatalysts with high H2O2 adsorption: Degradation mechanism, H2O2 activation process

The FeOCl-based photo-Fenton heterojunction catalyst holds great promise for effective water pollution treatment. A novel heterojunction FeOCl/MOF-In2S3 (F/M-I) was fabricated by coating hollow MOF-In2S3 nanoflowers onto the surface of FeOCl. Under the optimal conditions, the maximum photo-Fenton degradation rate constants of FeOCl/MOF-In2S3 for oxytetracycline (OTC) within 20 min is 0.88192 L mg−1·min−1, which are 3.2 and 2.5 times that of pure FeOCl (0.27357 L mg−1·min−1) and MOF-In2S3 (0.35222 L mg−1·min−1). Density functional theory (DFT) results confirm that the electron-rich nature of MOF-In2S3 accelerates the cycle between Fe (III)/Fe (II)of FeOCl, promoting H2O2 adsorption by FeOCl/MOF-In2S3 and generating more hydroxyl radicals (·OH) for pollutant degradation. Based on the results of DFT, combined with the results of the reactive oxidation species scavenger (ROSs), electron paramagnetic resonance (EPR) and Mott-Schottky curves, the separation and transfer behavior of photoexcited charges in FeOCl/MOF-In2S3 heterojunction and the possible photocatalytic degradation mechanism were investigated. Finally, a Z-scheme heterostructure is proposed to elucidate the catalytic mechanism. This study provides a new perspective on designing and synthesizing semiconductor materials for water treatment by photo-Fenton catalysis.

The property and mechanism of peroxymonosulfate activation boosted carbon cage encapsulated Mo2C/Bi2O2CO3 Z-scheme heterojunction for enhanced catalytic degradation and antibacterial activity

The regulation of heterogeneous material properties for the synergistic degradation of pollutants remains a challenge. Herein, cobalt-nitrogen co-doped carbon cage (NCC) encapsulated Mo2C nanoparticles boosting Bi2O2CO3 photocatalyst (Mo2C@NCC/BOC) we designed to achieve photoexcitation synergistic PMS activation. The degradation results revealed Mo2C@NCC/BOC could achieved 96.4 % tetracycline (TC) removal after only 5 min. The degradation rate was 3.1 times and 5.9 times higher than those of pure Bi2O2CO3 and pure Mo2C@NCC, respectively. The improved TC degradation performance could be attributed to the Z-scheme heterostructure, resulting in a higher conversion rate of photo-generated electrons into radicals. In addition, Co2+/Co3+ and Mo5+/Mo6+ dual ions redox cycle system effectively triggers the activation of HSO5− under visible light. The TC degradation pathways and intermediate toxicity, including the photocatalyticmechanism were evaluated in detail. This study provides novel perspectives on the rational design of atom co-sharing heterojunction photocatalysts in activating PMS for water remediation.

Rational Design of Z-Scheme Heterostructures Composed of Bi/Fe-Based MOFs for the Efficient Photocatalytic Degradation of Organic Pollutants

Rational Design of Z-Scheme Heterostructures Composed of Bi/Fe-Based MOFs for the Efficient Photocatalytic Degradation of Organic Pollutants

Indium oxide-based Z-scheme hollow core–shell heterostructure with rich sulfur-vacancy for highly efficient light-driven splitting of water to produce clean energy

Crafting an inorganic semiconductor heterojunction with defect engineering and morphology modulation is a strategic approach to produce clean energy by the highly efficient light-driven splitting of water. In this paper, a novel Z-scheme sulfur-vacancy containing Zn3In2S6 (Vs-Zn3In2S6) nanosheets/In2O3 hollow hexagonal prisms heterostructrue (Vs-ZIS6INO) was firstly constructed by an oil bath method, in which Vs-Zn3In2S6 nanosheets grew on the surfaces of In2O3 hollow hexagonal prisms to form a hollow core–shell structure. The obtained Vs-ZIS6INO heterostructrue exhibited much enhanced activity of the production of H2 and H2O2 by the light-driven water splitting. In particular, under visible light irradiation (λ > 420 nm), the rate of generation of H2 of Vs-ZIS6INO sample containing 30 wt% Vs-Zn3In2S6 (30Vs-ZIS6INO) could reach 3721 μmol g–1h−1, which was 87 and 6 times higher than those of Zn3In2S6 (43 μmol g–1h−1) and Vs-Zn3In2S6 (586 μmol g–1h−1), respectively. Meanwhile, 30Vs-ZIS6INO could exhibit the rate of H2O2 production of 483 μmol g–1h−1 through the dual pathways of indirect 2e– oxygen reduction (ORR) and water oxidation (WOR) without adding any sacrifice agents, far exceeding In2O3 (7 μmol g–1h−1) and Vs-Zn3In2S6 (58 μmol g–1h−1). The excellent photocatalytic activities of H2 and H2O2 generations of Vs-ZIS6INO sample might result from the synergistic effect of the sulfur vacancy, hollow core–shell structure, and Z-scheme heterostructure, which accelerated the electron delocalization, enhanced the absorption and conversion of solar energy, reduced the carrier diffusion distance, and ensured high REDOX ability. In addition, the possible photocatalytic mechanisms for the production of H2 and H2O2 were discussed in detail. This study provided a new idea and reference for constructing the novel and efficient inorganic semiconductor heterostructures by coordinating vacancy defect and morphology design to adequately utilize water splitting for the production of clean energy.

A direct polymeric carbon nitride/tungsten oxide Z-scheme heterostructure for efficient photocatalytic hydrogen generation via reforming of plastics into value-added chemicals

A direct polymeric carbon nitride/tungsten oxide Z-scheme heterostructure for efficient photocatalytic hydrogen generation via reforming of plastics into value-added chemicals

Enhanced photocatalytic degradation of oxytetracycline by Z-scheme heterostructure ZIF-8/Bi4O5Br2

Semiconductor photocatalysis technology has a wide range of application in the treatment of environmental pollution. In this study, the Z-scheme heterojunction photocatalyst ZIF-8/Bi4O5Br2 was synthesized by hydrothermal method. The morphology, structure, mechanism and photocatalytic performance of the materials were studied. Under simulated sunlight illumination for 60 minutes, the degradation efficiency of oxytetracycline (15 mg·L−1) reached 94.2 %. In light of density functional theory calculation and liquid chromatography-mass spectrometry, the attack sites and degradation pathways of OTC were determined. The consequence of free radical capture test and electron paramagnetic resonance detection showed that ·O2-, ·OH and h+ were the primary active substances. Based on the analysis above, the charge transfer principle of Z-scheme heterojunction was further elucidation. It inhibited the recombination of photo carriers and improved the photocatalytic performance. This work provides a hopeful measure for photocatalytic degradation of OTC by Z-scheme heterojunction composite.

Fabrication of NiFe-LDH/MoS2 2D/2D material to construct direct Z-scheme heterojunction for enhanced CO2 photocatalytic reduction under visible light irradiation

In recent years, the utilization of solar energy for conversion of CO2 into fuels has emerged as a promising strategy for mitigating the Greenhouse effect. However, transport efficiency of photogenerated carriers plays a crucial role in determining the efficacy of CO2 photocatalytic reaction. In this paper, a 2D/2D composite material consisting of NiFe-LDH/MoS2, presenting high efficiency in separating photogenerated electron-hole pairs, has been successfully synthesized using a straightforward hydrothermal method. XRD, XPS, FTIR and other characterization results proved that the composite was successfully prepared, and its unique direct Z-scheme heterostructure improved the efficiency of CO2 photocatalytic reduction effectively. The composite material NiFe-LDH/MoS2 demonstrated enhanced rate of photo-induced electron-hole pair separation comparing with pure NiFe-LDH. Apart from this, the charge transfer resistance was reduced simultaneously, the composite material exhibited perfect photocatalytic activity. In photocatalytic reduction reaction experiment, CO yield of NiFe-LDH/MoS2 can reach 10.72 μmol/g, which is 3.93-fold and 4.17-fold that of bare NiFe-LDH and MoS2. The cyclic test also shows that the catalyst has good stability under visible light irradiation.

Unraveling the photo-induced dynamic behavior of COF-based Z-scheme heterostructure monolithic aerogels

Unraveling the photo-induced dynamic behavior of COF-based Z-scheme heterostructure monolithic aerogels

Z-scheme S-modified Zn0.2Cd0.8S/α-Fe2O3 heterostructure for enhanced photoelectrochemical water oxidation

A Z-type heterojunction system is proven to be an efficient strategy to promote the separation of photo-generated carriers and maintain strong redox capacity for an enhanced photoanode. Herein, we synthesized a S-modified Fe2O3/Zn0.2Cd0.8S (Fe/ZCS) photoanode by one-pot hydrothermal treatment of FeOOH/Zn0.2Cd0.8S precursor film, followed by vapor deposition treatment. The as-synthesized S-modified Fe/ZCS displayed enhanced PEC water oxidation performance with a photocurrent density (2.76 mA cm−2) of about 2.63 times that of a pure phase Fe2O3 and 2.05 times that of Fe/ZCS at 1.23 VRHE. After 8 h of continuous operation, the photocurrent density retention rate was still 96.4 % demonstrating its satisfactory stability. Benefiting from the morphology of fine nanorods, the fabricated Z-scheme heterostructure exhibited strong oxidation–reduction ability and the well-distributed Fe(III)-SO42- bonds played key roles as the electron capture centers. The fabricated Z-scheme photoanode exhibited prospective applications in sustainable photoelectrochemical water oxidation.