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"heterojunctions"
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Classification and Characterization Methods for Heterojunctions
Heterojunction constructions are usually used to promote the separation of photocarriers and improve the photocatalytic activities. However, misuse and confusion often occur in current research because there are no unified rules for the classification and naming of heterojunctions. In order to avoid this problem, this review summarizes and standardizes the classification and naming rules of heterojunctions, based on different band structure distribution of the two semiconductors in heterojunctions and transfer paths of photogenerated carriers. Moreover, the distinctions in photogenerated carrier behavior among O–scheme heterojunction, Z–scheme heterojunction, and S–scheme heterojunction within type II heterojunction are clearly elucidated. Additionally, current methodologies for identifying heterojunction types, including metal–ion photo–deposition, in situ X–ray photoelectron spectroscopy, surface photovoltage spectroscopy, transient absorption spectroscopy, and cathodoluminescence spectrometry, are summarized. This review also highlights the applicability of various heterojunction types across different photocatalytic applications and suggests future directions for heterojunction research. Currently, there is no unified standard for the classification and nomenclature of heterojunctions. To address this issue, this article systematically summarizes and standardizes the classification and naming rules for heterojunctions. Furthermore, it provides a clear elucidation of the differences in photogenerated carrier behavior among O–scheme, Z–scheme, and S–scheme heterojunctions within the Type II heterojunction system.
Journal Article
Highly efficient photosynthesis of hydrogen peroxide in ambient conditions
Photosynthesis of hydrogen peroxide (H₂O₂) in ambient conditions remains neither cost effective nor environmentally friendly enough because of the rapid charge recombination. Here, a photocatalytic rate of as high as 114 μmol·g−1·h−1 for the production of H₂O₂ in pure water and open air is achieved by using a Z-scheme heterojunction, which outperforms almost all reported photocatalysts under the same conditions. An extensive study at the atomic level demonstrates that Z-scheme electron transfer is realized by improving the photoresponse of the oxidation semiconductor under visible light, when the difference between the Fermi levels of the two constituent semiconductors is not sufficiently large. Moreover, it is verified that a type II electron transfer pathway can be converted to the desired Z-scheme pathway by tuning the excitation wavelengths. This study demonstrates a feasible strategy for developing efficient Z-scheme photocatalysts by regulating photoresponses.
Journal Article
Layered double hydroxides‐based Z‐scheme heterojunction for photocatalysis
Layered double hydroxides (LDHs)‐based photocatalysts have generated widespread interest owing to their great potential for solving both energy and environmental issues through directly converting nonconsumable solar energy. Numerous methods have been investigated and analyzed in recent years to promote the photocatalytic efficiency of LDHs. Z‐scheme heterojunction that mimics the artificial photosynthesis is employed in photocatalysis owing to the outstanding advantages, such as high quantum efficiency, separation of redox sites, and low recombination of photocarriers. Herein, various LDHs‐based Z‐scheme heterojunction photocatalysts are briefly reviewed. Z‐scheme heterojunction associated with LDHs‐based materials exhibit high photocatalysis performance, and these types of hybrids are applied in photocatalytic H 2 O splitting, CO 2 reduction, and pollution degradation, which are introduced and summarized in detail. In the end, a brief conclusion focused on future challenges and expectations of LDH‐based Z‐scheme photocatalytic system is presented. We expect that more advances for LDH‐based Z‐scheme photocatalyst can be achieved in the field of photocatalysis in the coming days.
Journal Article
Electric-field tunable Type-I to Type-II band alignment transition in MoSe2/WS2 heterobilayers
Semiconductor heterojunctions are ubiquitous components of modern electronics. Their properties depend crucially on the band alignment at the interface, which may exhibit straddling gap (type-I), staggered gap (type-II) or broken gap (type-III). The distinct characteristics and applications associated with each alignment make it highly desirable to switch between them within a single material. Here we demonstrate an electrically tunable transition between type-I and type-II band alignments in MoSe
2
/WS
2
heterobilayers by investigating their luminescence and photocurrent characteristics. In their intrinsic state, these heterobilayers exhibit a type-I band alignment, resulting in the dominant intralayer exciton luminescence from MoSe
2
. However, the application of a strong interlayer electric field induces a transition to a type-II band alignment, leading to pronounced interlayer exciton luminescence. Furthermore, the formation of the interlayer exciton state traps free carriers at the interface, leading to the suppression of interlayer photocurrent and highly nonlinear photocurrent-voltage characteristics. This breakthrough in electrical band alignment control, interlayer exciton manipulation, and carrier trapping heralds a new era of versatile optical and (opto)electronic devices composed of van der Waals heterostructures.
Photoluminescence and photocurrent measurements indicate that MoSe
2
/WS
2
hetero-bilayers can be switched from type-I to type-II band alignment by applying a vertical electric field.
Journal Article
Classification and Characterization Methods for Heterojunctions (Adv. Mater. Interfaces 15/2025)
Type II Heterojunction In order to avoid the misuse and confusion of the classification and naming of different types of heterojunction in photocatalysis, this review categorizes Type II heterojunctions into O‐scheme, Z‐scheme and S‐scheme heterojunctions according to different transfer paths of photocarriers. More details can be found in article 2500191 by Hongna Zhang, Hai‐Ying Jiang, and co‐workers.
Journal Article
Asymmetrical electrohydrogenation of CO₂ to ethanol with copper–gold heterojunctions
Copper is distinctive in electrocatalyzing reduction of CO₂ into various energy-dense forms, but it often suffers from limited product selectivity including ethanol in competition with ethylene. Here, we describe systematically designed, bimetallic electrocatalysts based on copper/gold heterojunctions with a faradaic efficiency toward ethanol of 60% at currents in excess of 500 mA cm−2. In the modified catalyst, the ratio of ethanol to ethylene is enhanced by a factor of 200 compared to copper catalysts. Analysis by ATR-IR measurements under operating conditions, and by computational simulations, suggests that reduction of CO₂ at the copper/gold heterojunction is dominated by generation of the intermediate OCCOH*. The latter is a key contributor in the overall, asymmetrical electrohydrogenation of CO₂ giving ethanol rather than ethylene.
Journal Article
Interface engineering of charge-transfer excitons in 2D lateral heterostructures
The existence of bound charge transfer (CT) excitons at the interface of monolayer lateral heterojunctions has been debated in literature, but contrary to the case of interlayer excitons in vertical heterostructure their observation still has to be confirmed. Here, we present a microscopic study investigating signatures of bound CT excitons in photoluminescence spectra at the interface of hBN-encapsulated lateral MoSe
2
-WSe
2
heterostructures. Based on a fully microscopic and material-specific theory, we reveal the many-particle processes behind the formation of CT excitons and how they can be tuned via interface- and dielectric engineering. For junction widths smaller than the Coulomb-induced Bohr radius we predict the appearance of a low-energy CT exciton. The theoretical prediction is compared with experimental low-temperature photoluminescence measurements showing emission in the bound CT excitons energy range. We show that for hBN-encapsulated heterostructures, CT excitons exhibit small binding energies of just a few tens meV and at the same time large dipole moments, making them promising materials for optoelectronic applications (benefiting from an efficient exciton dissociation and fast dipole-driven exciton propagation). Our joint theory-experiment study presents a significant step towards a microscopic understanding of optical properties of technologically promising 2D lateral heterostructures.
The authors unveil the many-particle processes underpinning the formation of bound charge transfer excitons at the interface of hBN-encapsulated lateral MoSe
2
-WSe
2
heterostructures. The excitons can be tuned via interface (i.e. high quality lateral junction) and dielectric (i.e. hBN encapsulation) engineering.
Journal Article
Heterojunction photocatalysts for degradation of the tetracycline antibiotic: a review
Antibiotic pollution is a major health issue inducing antibiotic resistance and the inefficiency of actual drugs, thus calling for improved methods to clean water and wastewater. Here we review the recent development of heterojunction photocatalysis and application in degrading tetracycline. We discuss mechanisms for separating photogenerated electron–hole pairs in different heterojunction systems such as traditional, p–n, direct Z-scheme, step-scheme, Schottky, and surface heterojunction. Degradation pathways of tetracycline during photocatalysis are presented. We compare the efficiency of tetracycline removal by various heterojunctions using quantum efficiency, space time yield, and figures of merit. Implications for the treatment of antibiotic-contaminated wastewater are discussed.
Journal Article
ZnO-based heterostructures as photocatalysts for hydrogen generation and depollution: a review
Energy shortage and escalating pollution are major challenges globally. Heterogeneous photocatalysis is one of the most cost-effective methods for producing renewable energy and removing pollutants. In particular, ZnO nanostructures are promising photocatalysts that are economic, stable, and biologically safe. ZnO-based nanoheterostructures have been used for heavy metal reduction, organic pollutants degradation, photocatalytic hydrogen production, and drug mineralization. Here, we review ZnO-based nanoheterojunctions as photocatalysts for hydrogen production and pollutant degradation. Hydrogen production has reached 1200 mol g−1 h−1 using Ce-doped ZnO/ZnS heterojunction, with a 8.5-fold higher efficiency than bare ZnO. Nearly complete removal of a dye pollutant was achieved in 15 min using hybrid ethyl cellulose-modified g-C3N4/ZnO. Moreover, ZnO/Ag2WO4/Fe3O4 showed a 152% and 143% higher antibiotic degradation rate than bare Ag2WO4 and ZnO, respectively. We present methods to modify ZnO, including coupling with other semiconductors, metal/non-metal doping, and carbon-based materials coupling; and methods for charge divergence in binary and ternary ZnO-based nanocomposites.
Journal Article