Direct Z-scheme Heterostructure Research Articles

Construction of direct Z-scheme Sn3O4/WO3 heterostructure photocatalyst for enhanced Congo red degradation and Cr(Ⅵ) reduction performance

The development of well-designed architectures is crucial in accelerating the transport of photon-generated carriers in composite photocatalysts. In this study, a direct Z-scheme Sn3O4/WO3 (SW) photocatalyst was successfully fabricated utilizing a straightforward hydro/solvothermal approach, where Sn3O4 nanosheets (NSs) grew in-situ onto WO3 nanorods (NRs) uniformly. The optimal SW-2 composite exhibits a remarkable reduction rate of 93.5 % for Congo Red (CR) within 40 min, with a rate constant (k) of 0.075 min−1. This performance surpasses that of pristine Sn3O4 and WO3, which have rate constants of 0.027 min−1 and 0.018 min−1, respectively. Additionally, the SW-2 composite effectively removes 89.2 % of Cr(VI) over 100 min, achieving a k value of 0.019 min−1, which is higher than that of Sn3O4 (0.013 min−1) and WO3 (0.001 min−1). Furthermore, the photocatalytic degradation performance of the recovered samples retains their photocatalytic degradation performance after five consecutive experimental cycles, indicating excellent durability. The enhanced photocatalytic performance can be attributed to the construction of a direct Z-scheme heterostructure, which not only broadens the spectral response range, bur also ensures efficient separation of photoexcited carriers and fosters robust photo-redox capacity within the composite. This study is expected to provide some valuable insights into the design and synthesis of Z-scheme heterojunction photocatalysts, aimed at addressing pressing environmental pollution challenges.

Synthesis of a novel bismuth molybdite/iron oxide thin film for oxytetracycline degradation in a photoelectrocatalytic system

In this study, heterostructures based on Bismuth molybdite/iron oxide (Bi2MoO6/Fe2O3) thin films were fabricated by a dip-coating technique using precursor solutions. The heterostructures were deposited on fluorine-doped tin oxide glass substrates. From a detailed characterization using X-ray diffraction and X-ray photoelectron spectroscopy, the formation of the orthorhombic phase for Bi2MoO6 and the co-existence of hematite and maghemite in Fe2O3 was demonstrated. Meanwhile, the field emission scanning electron microscopy cross-section images confirm the formation of well-defined Bi2MoO6 film under the Fe2O3 deposition. The optical band gap energies for the heterostructure obtained were estimated from the diffuse reflectance spectra and ranged from 2.3 to 3.5 eV. Photoluminescence analysis revealed an improved separation and faster transfer of photogenerated electrons and holes for the Bi2MoO6/Fe2O3 (Het) film. The best oxytetracycline (OTC) removal percentage through photoelectrocatalytic treatment was 96.85% using the Het. Besides, were carried out the variation of parameters which affect the OTC photoelectrocatalytic degradation as pH, potential applied, and scavenger assay. The 1O2 was the oxidant predominate, which attack the OTC ring to initiate and accelerate the degradation process. Based on the analysis of degradation intermediates and characteristics of Bi2MoO6/Fe2O3, possible degradation pathways and mechanisms of OTC were displayed. An enhancement of oxytetracycline degradation efficiency of Het fabricated compared to pristine oxides was achieved mainly due to avoid the charge recombination of photogenerated electron-hole pairs provided by Direct Z-scheme heterostructure. Finally, the Het fabricated represents a promising material for efficient and sustainable pharmaceutical removal applications.

First-principles study of GeC/Ga2SO heterostructure as a potential direct Z-scheme photocatalyst for water splitting

The rational design of van der Waals heterostructure offers an effective avenue for improving the photocatalytic efficiency of individual two-dimensional materials, garnering extensive interest in recent years. Herein, the feasibility of GeC/Ga2SO heterostructure as a photocatalyst for overall water splitting has been explored based on the first-principles calculations. Our findings reveal that the electronic bandstructure of GeC/Ga2SO heterostructure can be engineered in staggered or straddling band alignment depending on stacking patterns. Particularly, in the GeC/Ga2SO heterostructure with staggered band alignment, an intrinsic built-in electric field is established at the interface with the direction from GeC to Ga2SO, facilitating the formation of a direct Z-scheme heterostructure. Also importantly, the band-edge positions of Z-scheme GeC/Ga2SO heterostructure cross the water redox potentials, providing adequate driving force for both the reduction and oxidation reactions of water. Gibbs free energy calculations demonstrated that the photocatalytic overall water splitting can proceed spontaneously in the neutral environment (pH = 7) under light irradiation. Moreover, GeC/Ga2SO heterostructure exhibits good thermal stability and a strong (magnitude in 105 cm−1) and broad (from visible to ultraviolet light) optical absorption. Finally, through applying the tensile strain, further enhancements in the optical absorption and carrier redox ability are achieved due to the favorable modulation in the bandgap. Therefore, all these features make GeC/Ga2SO heterostructure show great potential in the application of photocatalytic water splitting.

Transforming sunlight through ultrasonically engineered ZnO and g-C₃N₄ Z-scheme heterostructure for superior photocatalysis: Experimental and theoretical study

In this study, we enhanced ZnO photocatalytic activity by synthesizing nanostructures with high aspect ratio of exposed polar facets. Post-synthesis ultrasonication induced morphological reconfiguration, improving optoelectronic properties, charge carrier separation, photocurrent, and shifted the valence band edge potential to higher positive values, providing a heightened overpotential for hydroxyl radical formation. The resulting overpotential for hydroxyl radical formation significantly boosted phenol degradation under UV light. To extend photoresponse, we employed ultrasonication to create a direct Z-scheme heterostructure with gCN, preventing particle aggregation. The S-ZnO/gCN photocatalyst, exhibiting a highly ordered structure, demonstrated superior photocatalytic activity under solar light for phenol degradation. Experimental results showed that increased dissolved oxygen accelerated hydroquinone and catechol formation, enhancing phenol degradation. Experimental results were supported by theoretical calculations. This innovative approach not only improves ZnO photocatalytic activity but also broadens its application to solar light-driven reactions.

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.

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.

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.

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.

Constructing a 3D Bi2WO6/ZnIn2S4 direct Z-scheme heterostructure for improved photocatalytic CO2 reduction performance

Developing efficient heterojunction photocatalysts with enhanced charge transfer and reduced recombination rates of photogenerated carriers is crucial for harnessing solar energy in the photocatalytic CO2 reduction into renewable fuels. This study employed electrostatic self-assembly techniques to construct a 3D Bi2WO6/ZnIn2S4 direct Z-scheme heterojunctions. The unique 3D structure provided abundant active sites and facilitated CO2 adsorption. Moreover, the optimized Bi2WO6/ZnIn2S4 composite demonstrated an impressive CH4 yield of 19.54 μmol g−1 under 4 h of simulated sunlight irradiation, which was about 8.73 and 16.30-fold higher than pure ZnIn2S4 and Bi2WO6. The observed enhancements in photocatalytic performance are attributed to forming a direct Z-scheme heterojunction, which effectively promotes charge transport and migration. This research introduces a novel strategy for constructing photocatalysts through the synergistic effect of morphological interface modifications.

Direct Z-scheme β-SnSe/HfS2 heterostructure for photocatalytic water splitting: High solar-to-hydrogen efficiency and excellent carrier mobility

Constructing directly stacked Z-scheme van der Waals (vdW) heterostructures of different two-dimensional (2D) monolayers is one effective approach to developing highly efficient photocatalysts. In this study, a β-SnSe/HfS2 heterostructure is designed, and its electronic properties and photocatalytic water splitting performance are systematically investigated through first-principles calculations. The charge density difference and work function indicate the presence of an electric field within the heterostructure, further demonstrating its characteristic direct Z-scheme heterostructure. The heterostructure exhibits excellent photocatalytic activity with higher light absorption coefficients of up to 6.67 × 105 cm−1 in the visible and ultraviolet regions compared to the two monolayers alone. The heterostructure possesses high electron mobility in the x direction (2405.86 cm2s−1V−1) and high hole mobility in the y direction (537.56 cm2s−1V−1), facilitating the separation of electron-hole pairs. According to Gibbs free energy, the heterostructure can split water spontaneously overall in acidic settings and only needs an extra potential of 0.64 eV to do so in neutral situations. It is anticipated that the heterostructure have a solar-to-hydrogen (STH) efficiency of up to 14.29%. Because of this, the β-SnSe/HfS2 heterostructure possesses a significant amount of promise for use as a photocatalyst in the generation of hydrogen through the process of water splitting.

Direct Z-scheme MS2/Si2PAs (M = Zr, Hf) heterostructures for efficient water splitting: A first-principles study

Designing direct Z-scheme heterostructure is an effective strategy to enhance redox ability, greatly raising the attention of photocatalysis in recent years. Here, we design 24 diverse vertical MS2/Si2PAs (M = Zr, Hf) heterostructures with different stacking configurations. Four kinds of heterostructures with different interlayer contacts are taken as examples to investigate the geometry, stability, and electronic properties, as well as the photocatalytic mechanism based on the first-principles calculations. We find that the competitiveness of MS2/Si2PAs (M = Zr, Hf) heterostructures is attributed to their excellent visible light absorption (∼2 × 105 cm−1), ultrafast carrier migration (∼13 587.28 cm2 V−1 s−1), and high solar-to-hydrogen efficiency (10.02%), indicating that this kind of system can be as a promising candidate in the field of semiconductor photocatalysis.

A direct Z-scheme BS/PtO2 van der Waals heterojunction for enhanced visible-light photocatalytic water splitting: a first-principles study.

A direct Z-scheme heterostructure holds a unique advantage in solar-driven overall water splitting, while the rational design of efficient photocatalysts for water splitting in such heterostructures remains a challenge. Based on first-principles calculations, this study proposes a novel direct Z-scheme two-dimensional (2D) van der Waals (vdW) heterostructure photocatalyst, denoted as BS/PtO2. Its band edges match the oxidation-reduction potentials of water, satisfying the conditions for the oxidation and reduction of water. Under acidic conditions (pH = 0), the results of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) indicate that BS/PtO2 can drive the OER without the need for an external bias, while the HER requires catalytic assistance. Interestingly, compared to single-layer materials, this heterostructure exhibits a significant enhancement in visible light absorption, implying a more efficient solar energy conversion capability. Therefore, the BS/PtO2 heterostructure holds the potential to become a promising direct Z-scheme photocatalyst with efficient visible light activity.

Direct Z-scheme MoSTe/g-GeC heterostructure for photocatalytic water splitting: A first-principles study

In this paper, based on the first-principle calculations of hybrid density functional theory, the MoSTe/g-GeC of the Z-scheme heterostructure is constructed. The stability, electronic properties, optical absorption properties, and photocatalytic mechanism of the heterostructure is investigated. The band structure of MoSTe/g-GeC heterostructure is staggered, and the bandgap is 0.47 eV. The built-in electric field from g-GeC to MoSTe, with a size of 1.03 eV. The optical absorption coefficient of MoSTe/g-GeC heterostructures is significantly higher than that of MoSTe and g-GeC layer. When pH ranges from 0 to 7, the reduction reaction occurs in g-GeC layer, and the oxidation reaction occurs in the MoSTe layer. In the MoSTe/g-GeC heterostructure under different stresses, the band structure is arranged in a staggered manner. Importantly, under tensile strain, the bandgap of MoSTe/g-GeC heterostructure can be changed from the indirect into a direct bandgap. The bandgap of heterostructure decreases under the strain. In addition, the analysis of the photocatalytic mechanism shows that the redox reaction of the MoSTe/g-GeC heterostructure occurs on the layer with strong redox ability, and their light absorption ability is significantly enhanced compared to single-layers, which effectively improves the photocatalytic properties. It's a potential high-efficiency photocatalytic materials for direct Z-scheme heterostructure.

Electronic properties and applications of MoSSe/MoSTe heterostructure in photocatalytic water splitting

Monolayer material’s electronic properties can be controlled by constructing heterostructures, such as transition metal dichalcogenides (TMDCs) heterostructures. Among them, heterostructures with a new direct Z-scheme electronic band structure are promising solar-driven water splitting photocatalysts. In this work, the first principle calculation based on Density functional theory (DFT) was used to study the structure, electrical properties and optical properties of MoSSe/MoSTe heterostructures. By vertically stacking MoSSe and MoSTe monolayers and via lattice relaxation, 12 different MoSTe/MoSSe heterostructure models have been constructed. Model 1 (TeMoS/SeMoS) and model 2 (SMoTe/SMoSe) are novel direct Z-scheme heterostructure and traditional type II band configurations, respectively. Compared to type II heterostructures, direct Z-scheme arrangement can achieve more efficient spatial separation of photogenerated carriers, increase the lifetime of minority carriers while retaining the redox ability of internal carriers. And compared to monolayer materials, MoSTe/MoSSe heterostructures exhibit stronger and broader optical absorption. Additionally, the conduction band edge potential of MoSTe in the heterostructure is negative to the H+/H2O electrode potential, and the valence band edge potential of MoSSe is positive to the O2/H2O electrode potential. It can be inferred that MoSTe/MoSSe heterostructure has strong reduction and oxidation capabilities, and can achieve total water-splitting reaction. Further Gibbs free energy calculation found that the MoSSe/MoSTe heterostructure can spontaneously conduct thermodynamic water splitting under the light in both acidic and neutral environments, and the theoretical hydrogen production efficiency is 16.7 %.

Construction of Z-Scheme MoS2/ZnFe2O4 heterojunction photocatalyst with enhanced photocatalytic activity under visible light

Construction of direct Z-scheme heterostructure photocatalysts with improved photogenerated charge carriers has gained considerable attention during the past few years. In this work, a direct Z-scheme MoS2/ZnFe2O4 heterostructure photocatalyst was synthesized via a facile hydrothermal method. The photocatalytic activity of this photocatalyst was evaluated through degradation of methylene blue (MB) dye under visible light irradiation. The MZF-25 catalyst showed high catalytic activity with a degradation efficiency of 92.3%, higher than that of pristine MoS2 and ZnFe2O4. Further, the reusability of the MoS2/ZnFe2O4 heterostructure was analysed and there was no significant loss in the photocatalytic activity even after four cycles. Finally, the Z-scheme mechanism of the MoS2/ZnFe2O4 photocatalyst was determined for the degradation of MB. This work provides a promiosing strategy for designing MoS2/ZnFe2O4-based Z-scheme heterostructures for removal of organic pollutants.

Design of a direct Z-scheme GeC/arsenene van der Waals heterostructure as highly efficient photocatalysts for water splitting

The utilization of heterostructures as photocatalysts for water decomposition is a promising method to tackle contemporary environmental challenges. This research paper presents the design of a direct Z-scheme heterostructure utilizing a monolayer of GeC and a monolayer of arsenene, based on first-principle calculations. The photocatalytic efficiency of this GeC/arsenene van der Waals (vdW) heterostructure in a direct Z scheme has been investigated. The presence of a built-in electric field from the GeC monolayer to the arsenene monolayer has been established through an analysis of band alignment, work function, charge density, and Bader charge. The GeC/arsenene heterostructure exhibits excellent and robust optical absorption efficiency for the sunlight, alongside achieving the maximum solar-to-hydrogen (STH) energy conversion efficiency, amounting to 7.28%, under a biaxial strain of +4%. Furthermore, the Gibbs free energy changes in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) of the GeC/arsenene heterostructure have been calculated. The outcomes indicate that the GeC/arsenene heterostructure is a feasible semiconductor for photocatalytic water splitting.

Construction of Bi2MoO6/CoWO4 Z-scheme heterojunction for high-efficiency photocatalytic degradation of norfloxacin under visible light: Performance and mechanism insights

In this work, we employed Bi2MoO6 and CoWO4 to fabricate a direct Z-scheme Bi2MoO6/CoWO4 (BMC-x) heterostructure with high redox potential for norfloxacin (NOR) photodegradation. Under visible light (λ > 420 nm) illumination, BMC-x composites displayed excellent photodegradation performance toward norfloxacin. The photodegradation rate of norfloxacin by BMC-30 reached 97.1% within 60 min of illumination, and the apparent rate constant (0.0588 min−1) was 2.42 and 17.8 times those of Bi2MoO6 and the CoWO4, respectively. The photocatalytic performance of BMC-x nanocomposites was mainly ascribed to the more efficient utilization of electrons (e−) and holes (h+) due to the fabrication of a direct Z-scheme heterostructure. In addition, the mechanisms of NOR degradation were investigated through active species capture experiments and ESR analyses, indicating that O− 2and h+ worked as primary components. Furthermore, the NOR photodegradation pathways were investigated by density functional theory (DFT) and intermediates analysis. More importantly, depending on the QSAR predictions and E.colicultivation, the comprehensive toxicity of the final intermediates was lower than that of the parent. Thus, this work offers a feasible idea for the design and construction of Z-scheme heterojunctions for the highly effective degradation of emerging contaminants in water.

Internal electric field enhanced photoelectrochemical water splitting in direct Z-scheme GeC/HfS2 heterostructure: A first-principles study

Designing direct Z-scheme heterostructure photocatalysts has received enormous attention due to the efficient separation of photo-generated carriers in water splitting. Based on first-principles calculations, electronic properties and a photocatalytic mechanism of a GeC/HfS2 van der Waals (vdW) heterostructure are systematically explored. From the analysis of band arrangement and the built-in electric field, the heterostructure, with an indirect bandgap of 0.40 eV, is demonstrated to be a typical direct Z-scheme system. Remarkably, there is also a 0.40 eV interlayer work function difference in the heterostructure, which is helpful to further drive carrier separation and enhance the water splitting ability by partially bending the redox potential of water. The Gibbs calculation shows that the GeC/HfS2 vdW heterostructure can achieve overall photocatalytic water splitting spontaneously under neutral conditions. Moreover, excellent visible light absorption ability (∼5×105 cm−1) and giant carrier mobilities (5823 cm2 V−1 s−1) also make GeC/HfS2 heterostructure highly competitive in numerous photocatalytic materials and optoelectronic devices. The bandgap can be flexibly adjusted by biaxial strain, enabling a wider application of the heterostructure. All these significant properties not only demonstrate the great application potential of GeC/HfS2 heterostructure as photocatalysis but also provide ideas for designing novel electric field-enhanced heterostructures.

Direct Z-Scheme SnSe2/SnSe Heterostructure Passivated by Al2O3 for Highly Stable and Sensitive Photoelectrochemical Photodetectors.

To mimic the natural photosynthesis system, a Z-scheme heterostructure is proposed as a viable and effective strategy for efficient solar energy utilization such as photocatalysis and photoelectrochemical (PEC) water splitting due to the high carrier separation efficiency, fast charge transport, strong redox, and wide light absorption. However, it remains a huge challenge to form a direct Z-scheme heterostructure due to the internal electric-field restriction and vital band-alignment at the interface. Herein, the van der Waals heterostructure based on the allotrope SnSe2 and SnSe is designed and synthesized by a two-step vapor phase deposition method to overcome the limitation in the formation of the Z-scheme heterostructure for the first time. The Z-scheme heterostructure of SnSe2/SnSe is confirmed by X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, PEC measurement, density functional theory calculations, and water splitting. Strikingly, the PEC photodetectors based on the Z-scheme heterostructure show a synergistic effect of superior stability from SnSe and fast photoresponse from SnSe2. As such, the SnSe2/SnSe Z-scheme heterostructure shows a good photodetection performance in the ultraviolet to visible wavelength range. Furthermore, the photodetector shows a faster response/recovery time of 13/14 ms, a higher photosensitivity of 529.13 μA/W, and a higher detectivity of 4.94 × 109 Jones at 475 nm compared with those of single components. Furthermore, the photodetection stability of the SnSe2/SnSe is also greatly improved by a-thin-Al2O3-layer passivation. The results imply the promising rational design of a direct Z-scheme heterostructure with efficient charge transfer for high performance of optoelectronic devices.

Exploring the effects of different crystal facet combinations and I-doping in the BiOCl/BiOI heterostructure on photocatalytic properties: a hybrid density functional investigation.

This study uses hybrid functional calculations to investigate the effects of various crystal facet combinations in BiOCl and BiOI on the photocatalytic activity of the BiOCl/BiOI heterostructure. The results show that the separation efficiencies of photo-generated electron-hole pairs in BiOCl(010)/BiOI(001) and BiOCl(010)/BiOI(010) are constrained by type I band alignments in principle. In contrast, BiOCl(001)/BiOI(001) and BiOCl(001)/BiOI(010) heterostructures, which operate under the direct Z-scheme type, exhibit an enhanced photo-generated charge separation efficiency, superior redox capacity, and enhanced visible light absorption. Specifically, BiOCl(001)/BiOI(010) exhibits a more remarkable reduction ability that can reduce O2 to ˙O2-. Furthermore, our investigations demonstrate that targeted I element doping in BiOCl(001)/BiOI(010) can reduce the band gap of the BiOCl(001) sheet, enhance visible light absorption, and maintain the direct Z-scheme characteristics, thereby further improving the photocatalytic performance. Additionally, we discovered that I doping can transform the BiOCl(010)/BiOI(001) heterostructure from type I into a direct Z-scheme heterostructure, resulting in a substantial enhancement in the separation efficiency and reduction ability of photo-generated carriers as well as visible light absorption with increasing I doping concentration. Considering the excellent charge injection efficiency observed in experiments with the BiOCl(010)/BiOI(001) heterostructure, I-BiOCl(010)/BiOI(001) may represent a superior photocatalyst. Thus, this study highlights the crucial and substantial roles of engineering specific crystal facet combinations and I doping in enhancing the photocatalytic performance of the BiOCl/BiOI heterostructure. This theoretical study contributes to the comprehension of related experimental findings and offers valuable insights for the development of novel BiOCl/BiOI heterostructures with superior photocatalytic activity.