Dual Heterojunction Research Articles

Simulation And Design of a Vertical Gallium Nitride JFET with Dual Lateral Heterojunction Channels

A novel vertical gallium nitride (GaN) junction field-effect transistor (JFET) is reported in this article. Through the setup of dual lateral heterojunction channels in the body, the current density is high while the p-type gallium nitride growth area can be adjusted to easily achieve enhanced mode. Based on the structure parameter settings in this article, through the device simulation software TCAD, and under the condition of selecting the appropriate p-type GaN growth region, the threshold voltage of the device is 1.1 V, the source output current density can reach 7.2 kA/cm2, the breakdown voltage is about 750 V, and the on-resistance is 0.52 mΩ·cm2. Finally, the test circuit is built, and the switching characteristics of the device proposed in this paper are simulated under the consideration of parasitic inductance.

Dual Heterojunctions and Nanobowl Morphology Engineered BiVO4 Photoanodes for Enhanced Solar Water Splitting.

Photoelectrochemical (PEC) water splitting represents an attractive strategy to realize the conversion from solar energy to hydrogen energy, but severe charge recombination in photoanodes significantly limits the conversion efficiency. Herein, a unique BiVO4 (BVO) nanobowl (NB) heterojunction photoanode, which consists of [001]-oriented BiOCl underlayer and BVO nanobowls containing embedded BiOCl nanocrystals, is fabricated by nanosphere lithography followed by in situ transformation. Experimental characterizations and theoretical simulation prove that nanobowl morphology can effectively enhance light absorption while reducing carrier diffusion path. Density functional theory (DFT) calculations show the tendency of electron transfer from BVO to BiOCl. The [001]-oriented BiOCl underlayer forms a compact type II heterojunction with the BVO, favoring electron transfer from BVO through BiOCl to the substrate. Furthermore, the embedded BiOCl nanoparticles form a bulk heterojunction to facilitate bulk electron transfer. Consequently, the dual heterojunctions engineered BVO/BiOCl NB photoanode exhibits attractive PEC performance toward water oxidation with an excellent bulk charge separation efficiency of 95.5%, and a remarkable photocurrent density of 3.38mA cm-2 at 1.23 V versus reversible hydrogen electrode, a fourfold enhancement compared to the flat BVO counterpart. This work highlights the great potential of integrating dual heterojunctions engineering and morphology engineering in fabricating high-performance photoelectrodes toward efficient solar conversion.

Visible-light induced tetracycline degradation catalyzed by dual Z-scheme InVO4/CuBi2O4/BiVO4 composites: The roles of oxygen vacancies and interfacial chemical bonds

Dual Z-scheme InVO4/CuBi2O4/BiVO4 (CuInBi) composites with rich oxygen vacancies and chemical bonds at the heterojunction interfaces were fabricated, for the first time, through hydrothermal method with post annealing treatment, in which CuBi2O4 acts as a bridge to connect InVO4 and BiVO4. The as-prepared composites exhibited superior photocatalytic activity compared with the individual semiconductors. Specifically, the degradation rate of tetracycline (20 mg/L) in the presence of CuInBi-1 (1.0 g/L) was up to 5.4, 2.8, and 3.1 times faster than those in the presence of CuBi2O4, InVO4, and BiVO4, respectively. The enhanced photocatalytic performance could be partially attributed to the good light absorption of CuBi2O4, which broadens the visible light response of the InVO4/CuBi2O4/BiVO4 composites. Meanwhile, the interfacial chemical bonds in the dual Z-scheme heterojunction help accelerate charge separation and maintain strong redox activity. In addition, the oxygen vacancies, induced mainly by the low-valent vanadium atoms, facilitate the production of singlet oxygen (1O2) through energy transfer, which easily attacks the electron-rich groups, including phenolic group, dimethylamino group, amine group, and double bonds, in tetracycline. The InVO4/CuBi2O4/BiVO4 composite exhibited excellent reusability and stability, and performed well in photocatalytic degradation of tetracycline in river water and under natural sunlight, demonstrating great potential for practical application. The probable photocatalytic mechanism of InVO4/CuBi2O4/BiVO4 composite was proposed according to the results of density functional theory (DFT) calculations, and the reactive oxygen species (ROSs) and major degradation intermediates detected in the photocatalytic system. This work demonstrates the important roles of oxygen vacancies and interfacial chemical bonds in boosting the photocatalytic activity of Z-scheme heterojunctions and provides a reference for the construction of high-activity photocatalysts for efficient degradation of antibiotics.

Internal electric fields drive dual S-scheme heterojunctions: Insights into the role of the triple interlaced lattice

The internal electric field induced by the lattice interfaces in a heterojunction can facilitate charge transfer, thereby improving the photocatalytic performance. However, the details of the relationship between the lattice interfaces and the charge transfer mechanism in heterojunctions remain unclear. In this study, a Bi2WO6/Bi2O2CO3/C3N4 heterojunction (BBC) with an interlaced lattice was prepared, and the role of the interlaced lattice in charge transfer was revealed. Compared to pristine Bi2O2CO3, Bi2WO6, and C3N4, BBC exhibited an increased ciprofloxacin degradation rate constant (0.0573 min−1). A series of experiments were performed to reveal the role of the interlaced lattice interface in the enhanced photocatalytic performance. The results show that the driving force provided by the interlaced lattice interface changes the charge transfer mechanism from a dual Ⅱ-scheme to a dual S-scheme. This work provides profound insights into the effects of lattice interfaces in heterojunctions and the design of efficient photocatalysts.

Integration of high visible-light-driven ternary dual Z-scheme AgVO3-InVO4/g-C3N4 heterojunction nanocomposite for enhanced uranium(VI) photoreduction separation

With deepening application of nuclear power technology, the problem of water ecological environment pollution caused by uranium (U(VI)) is becoming increasingly serious. Photoreduction separation of U(VI) on photocatalysts is considered as an effective strategy to solve uranium pollution. In this work, a novel ternary dual Z-scheme AgVO3-InVO4/g-C3N4 heterojunction (Z-AIGH) nanocomposite with high surface area (73.45 m2 g−1, Z-AIGH2) was designed. The batch adsorption experiment in dark environment showed that Z-AIGH2 nanocomposite had an excellent U(VI) adsorption performance. As for photocatalytic experiments, Z-AIGH2 exhibited a rapid photocatalytic response for separating U(VI) without any organic sacrifice agents. The U(VI) separation rate on Z-AIGH2 nanocomposite was over 98.7% after only 20.0 min visible light irradiation (T = 298 K, CU(Ⅵ) = 10.0 mg L−1, m/V = 0.1 g L−1 and pH = 7.0). Z-AIGH2 nanocomposite also showed good selectivity and cycle stability. The U(VI) removal rate of Z-AIGH2 nanocomposite after fifth cycles was about 96.1% (T = 298 K, CU(Ⅵ) = 10.0 mg L−1, m/V = 0.1 g L−1 and pH = 7.0). High photocatalytic activity of Z-AIGH2 for U(VI) was attributed to the construction of ternary dual Z-scheme heterojunction structure and ant nest-like hole structure. Based on above results, Z-AIGH2 nanocomposite had great potential for water environment renovation.

Sensitive dual-mode sensing platform for Amyloid β detection: Combining dual Z-scheme heterojunction enhanced photoelectrochemistry analysis and dual-wavelength ratiometric electrochemiluminescence strategy

As a tumor biomarker, the accumulation of amyloid β oligomers (Aβo) in the brain has been suggested as a key feature in the pathogenesis and progression of Alzheimer's disease (AD). In this work, we designed a novel photoelectrochemical (PEC) and electrochemiluminescence resonance energy transfer (ECL-RET) dual-mode biosensor to achieve ultra-sensitive detection of Aβo. Specifically, the electrode surface modified Carbon Dots (C Dots) and the electrodeposited polyaniline (PANI) film formed a Z-scheme heterojunction reversing the photocurrent signal, and then the Aβo specific recognition peptide was attached to the surface via amide bonding between the amino group of PANI and carbonyl group of peptide. After that, in the presence of CdTe labeled specific recognition aptamer for Aβ (CdTe-Apt), Aβo was captured to construct a sandwich-type biosensor and exhibited a significantly enhanced cathodic photocurrent response because the formed dual Z-scheme heterojunction promoted charge separation efficiency. Interestingly, the proposed biosensor also caused a ratiometric change in the ECL intensity at 555 nm and 640 nm. Therefore, the developed biosensor achieved dual-mode detection of Aβo, where the PEC detection range of Aβo was from 10 fM to 0.1 μM (with a detection limit of 4.27 fM) and the ECL method provided a linear detection range of 10 fM to 10 nM (with a detection limit of 6.41 fM). The stability and reliability of the experimental results indicate that this has been a promising biosensing pattern and could be extended to the analysis of other biomarkers.

Unique roles of exfoliated bentonite in S-scheme BiOBr/Bi2MoO6 heterojunction for boosted ciprofloxacin degradation

S-scheme heterojunction retained the strong redox potential of catalysts, yet confronting severe photocorrosion and particle agglomeration, resulting in poor stability. Herein, the dual Bi-based S-scheme heterojunction supported by exfoliated bentonite (BiOBr/Bi2MoO6/BTex) was fabricated via a facile microwave hydrothermal strategy. BTex could promote the dispersion of photocatalysts and reinforce heterojunction stability through intensive surface interaction, thus reducing leakage of metal ions. The optimal BiOBr/10% Bi2MoO6/BTex exhibited excellent visible light photocatalytic performance and 94% ciprofloxacin (CIP) could be degraded within 120 min. Furthermore, the high catalytic efficiency could be maintained within the pH range from 5 to 9, and efficient degradation of tetracycline and dyes could also be achieved. Basing the analysis of band structures and determination of active species, enhanced separation and migration efficiency of photogenerated carriers could be ascribed to the synergistic effect of internal electron field (IEF) from heterojunction and surface charge repulsion from BTex. Additionally, the susceptible sites of CIP were obtained by density functional theory calculations, and three possible degradation pathways, including breakage of the quinolone ring, oxidation of the piperazine ring and defluorination were speculated combined with HPLC-MS results. With prolonging photocatalysis time, the diminished toxicity of intermediates was confirmed. This study supplied new insights to improve performance and control morphology of S-scheme heterojunctions by introducing cost-effective nature bentonite.

Synthesis of Dual Z-Scheme CuBi2O4/Bi2Sn2O7/Sn3O4 Photocatalysts with Enhanced Photocatalytic Performance for the Degradation of Tetracycline under Visible Light Irradiation

The dual Z-scheme heterojunction CuBi2O4/Bi2Sn2O7/Sn3O4(CBS) was successfully constructed through in situ growth methods, and its photocatalytic performance was evaluated via degradation of tetracycline hydrochloride under visible light. Out of all samples, CBS-2 exhibited the highest photocatalytic activity, with an apparent rate constant of 2.34, 20.16, and 44.17 times that of Bi2Sn2O7, CuBi2O4, and Sn3O4, respectively. Even after four cycles, the photocatalytic efficiency remained above 85%. The improvement can be attributed to the construction of the Z-scheme heterojunction, which effectively promotes the separation and migration of photogenerated carriers. The possible photocatalytic degradation mechanism of dual Z-scheme heterojunction CBS was deduced based on the theory of free radical capture and energy band.

Enhanced electron channel via the interfacial heterotropic electric field in dual S-scheme g-C3N4/WO3/ZnS photocatalyst for year-round antibiotic degradation under sunlight

Widespread and persistent presence of antibiotic contaminants in natural aquatic environments has aroused all mankind concern due to their potential threat to human health. Photocatalysis represents a promising means to remediate polluted waters with the simple assistance of solar energy. In this context, the feasibility of treating antibiotic contaminated water with g-C3N4/WO3/ZnS dual S-scheme heterojunction driven by interfacial heterotropic electric field was investigated under year-round climate conditions. The optimum composite (5-CWZ) could degrade >85% of tetracycline within 1 h of summer sunlight and 1.5 h of winter sunlight irradiation. The results of electron spin resonance (ESR), chemical trapping experiment, High performance liquid chromatography mass spectrometry (HPLC-MS), ultraviolet photoelectron spectroscopy (UPS) and density functional theory (DFT) calculation reflected that in-situ anchoring of WO3 and ZnS on the surface of g-C3N4 facilitates the formation of interfacial heterotropic electric field which were effective towards low-resistance charge carrier channelization, resulting sufficient •O2–, h+, •OH species evolving for attacking the active atoms of contaminants with high Fukui index. Furthermore, the retention of superior photocatalytic properties in complex actual water matrices together with the non-toxicity of both 5-CWZ photocatalyst and treated TC solution proved by Pisum sativum bud radicle elongation and bacterial (E. coli and B. subtilis) cultivation further demonstrated the feasibility of the 5-CWZ to treat antibiotics in real water under irradiation of solar light.

Self-Powered Photodetector with High Efficiency and Polarization Sensitivity Enabled by WSe2/Ta2NiSe5/WSe2 van der Waals Dual Heterojunction.

Self-powered photodetectors have triggered widespread attention because of the requirement of Internet of Things (IoT) application and low power consumption. However, it is challenging to simultaneously implement miniaturization, high quantum efficiency, and multifunctionalization. Here, we report a high-efficiency and polarization-sensitive photodetector enabled by two-dimensional (2D) WSe2/Ta2NiSe5/WSe2 van der Waals (vdW) dual heterojunctions (DHJ) along with a sandwich-like electrode pair. On account of enhanced light collection efficiency and two opposite built-in electric fields at the hetero-interfaces, the DHJ device achieves not only a broadband spectral response of 400-1550 nm but outstanding performance under 635 nm light illumination including an ultrahigh external quantum efficiency (EQE) of 85.5%, a pronounced power conversion efficiency (PCE) of 1.9%, and a fast response speed of 420/640 μs, which is much better than that of the WSe2/Ta2NiSe5 single heterojunction (SHJ). Significantly, based on the strong in-plane anisotropy of 2D Ta2NiSe5 nanosheets, the DHJ device shows competitive polarization sensitivities of 13.9 and 14.8 under 635 and 808 nm light, respectively. Furthermore, an excellent self-powered visible imaging capability based on the DHJ device is demonstrated. These results pave a promising platform for realizing self-powered photodetectors with high performance and multifunctionality.

Heterogeneous photo-Fenton catalyst α-Fe2O3@g-C3N4@NH2-MIL-101(Fe) with dual Z-Scheme heterojunction for degradation of tetracycline

A novel photo-Fenton catalyst α-Fe2O3@g-C3N4@NH2-MIL-101(Fe) (FGN) with dual Z-scheme heterojunction was successfully prepared by hydrothermal method to degrade tetracycline (TC). The preparation conditions were optimized by orthogonal test, and the successful synthesis was confirmed by characterization analyses. The prepared FGN showed better light absorption performance, higher photoelectrons-holes separation efficiency, lower photoelectrons transfer resistance, and higher specific surface area and pore capacity compared with α-Fe2O3@g-C3N4 and α-Fe2O3. The effects of experimental conditions on the catalytic degradation of TC were investigated. The degradation rate of 10 mg/L TC could reach 98.33% within 2 h when the dosage of FGN was 200 mg/L, and the degradation rate could remain 92.27% after 5 times of reuse. Furthermore, the XRD spectra and XPS spectra of FGN before and after reuse were compared to explore the structural stability and catalytic active sites of FGN, respectively. According to the identification of oxidation intermediates, three degradation pathways of TC were proposed. Through H2O2 consumption experiment, radical-scavenging experiments, EPR results, the mechanism of the dual Z-scheme heterojunction was proved. The improved performance of FGN was attributed to the dual Z-Scheme heterojunction effectively promoting the separation of photogenerated electrons from the holes and accelerating the electrons transfer, and the increase of the specific surface area.

Graphitic carbon nitride (g–C3N4)–assisted materials for the detection and remediation of hazardous gases and VOCs

Graphitic carbon nitride (g–C3N4)–based materials are attracting attention for their unique properties, such as low-cost, chemical stability, facile synthesis, adjustable electronic structure, and optical properties. These facilitate the use of g-C3N4 to design better photocatalytic and sensing materials. Environmental pollution by hazardous gases and volatile organic compounds (VOCs) can be monitored and controlled using eco-friendly g–C3N4– photocatalysts. Firstly, this review introduces the structure, optical and electronic properties of C3N4 and C3N4 assisted materials, followed by various synthesis strategies. In continuation, binary and ternary nanocomposites of C3N4 with metal oxides, sulfides, noble metals, and graphene are elaborated. g-C3N4/metal oxide composites exhibited better charge separation that leads to enhancement in photocatalytic properties. g-C3N4/noble metal composites possess higher photocatalytic activities due to the surface plasmon effects of metals. Ternary composites by the presence of dual heterojunctions improve properties of g-C3N4 for enhanced photocatalytic application. In the later part, we have summarised the application of g-C3N4 and its assisted materials for sensing toxic gases and VOCs and decontaminating NOx and VOCs by photocatalysis. Composites of g-C3N4 with metal and metal oxide give comparatively better results. This review is expected to bring a new sketch for developing g–C3N4–based photocatalysts and sensors with practical applications.

Novel dual Z-scheme Ag-bridged AgI/FeVO4-C3N4 plasmonic heterojunction: A study on the performance and mechanism of photocatalytic reduction of Cr(VI)

Proper design and synthesis of photocatalysts with efficient interfacial charge transfer, strong redox capabilities, and robust environmental applications are essential. Herein, a novel dual Z-scheme Ag-bridged AgI/FeVO4-C3N4 plasmonic heterojunction was successfully synthesized by a chemical deposition method. Compared with FeVO4, FeVO4-C3N4, AgI/C3N4, AgI/FeVO4, and AgI/FeVO4-C3N4, the optimized dual Z-scheme Ag@AgI/FeVO4-C3N4 composite exhibited an excellent photocatalytic reduction of Cr(VI) in water with approximately 100% reduction efficiency within 60 min. The reduction rate of Cr(VI) by Ag@AgI/FeVO4-C3N4 was estimated to be 0.0525 min−1, which was 3.5-fold and 26.2-fold of that by AgI/FeVO4-C3N4 and FeVO4, respectively. In addition, Ag@AgI/FeVO4-C3N4 showed good properties in terms of catalytic activity and 5 cycles stability. Furthermore, the reactive oxygen species •O2- and •OH enhancement processes were further verified by nitroblue tetrazolium (NBT) and terephthalic acid (TA) conversion experiments, respectively. Due to the strong force between AgI and FeVO4-C3N4 and the local surface plasmon resonance (LSPR) effect of Ag, a double Z-scheme heterojunction with rapid electron transfer ability was formed, which improved the photocatalytic performance of Ag@AgI/FeVO4-C3N4. Therefore, the new dual Z-scheme heterojunction Ag@AgI/FeVO4-C3N4 composites have a good application prospect in water purification. This study provides a new idea for the design of high-efficiency double Z-scheme photocatalysts and their application in the field of environmental purification.

1D/3D trepang-like N-modified carbon confined bimetal carbides and metal cobalt: Boosting electron transfer via dual Mott-Schottky heterojunctions triggered built-in electric fields for efficient hydrogen evolution and tri-iodide reduction

Tailoring the electronic structure of active centres is a critical strategy for improving the activity of catalysts, but its implementation still remains challenging. Herein, advanced 1D/3D trepang-like N-modified carbon confined Co and Co6Mo6C2 nanoparticles (namely Co6Mo6C2/Co@NC), a dual Mott-Schottky heterojunctions catalyst, is elaborately fabricated by utilizing bimetallic-ZIF and phosphomolybdic acid hydrate. The robust built-in electric field triggered by the dual Mott-Schottky heterojunctions composed of the Co6Mo6C2 and Co with N-modified carbon contact interfaces (Co6Mo6C2|NC and Co|NC) is favorable for transferring electrons and optimizing the electronic structures of the active centres near the Co6Mo6C2|NC and Co|NC interfaces. The 1D/3D Co6Mo6C2/Co@NC achieves a small Tafel slope of 58 mV dec−1. The photovoltaic device assembled with the Co6Mo6C2/Co@NC delivers a power conversion efficiency of 8.45 %. This work not only provides a new avenue for synthesizing high-performance carbon-confined metal and carbide electrocatalysts but also offers valuable insights into the synergistic effect of dual Mott-Schottky heterojunctions.

2D Ti3C2 MXene interfaced ZnO/WO3 thin film nanostructures towards improved photoelectrochemical water splitting

We explored the morphology evolution approach for sustained photoelectrochemical (PEC) water splitting by developing dual heterojunction. Herein, novel ZnO/WO3/Ti3C2 photoelectrode has been developed for the first time by the integration of flake-like ZnO, nanocrystal featured WO3, and layer-structured two-dimensional (2D) Ti3C2 MXene morphologies towards PEC activity under simulated solar light. By adjusting the radio frequency (RF) magnetron sputtering and post-annealing, flake-like/nanocrystals featured ZnO/WO3 heterostructure observed with uniform growth of WO3 nanocrystals over the flake-like ZnO. Further, efficient integration of layer-structured 2D Ti3C2 MXene on ZnO/WO3 was provided through spin-coating. Utilizing robust surface interface between ZnO, WO3, and Ti3C2, optical transmittance and band gap have been modified. Accordingly, ZnO/WO3/Ti3C2 improved the photocurrent generation about 1.4 × 10−3 A/cm2 compared to pure ZnO (7.8 × 10−4 A/cm2) and ZnO/WO3 (1.1 × 10−3 A/cm2) at +0.4 V. These findings further provided a photoconversion efficiency of 1.16 % by the ZnO/WO3/Ti3C2 at +0.4 V. The PEC studies proved that electrically conductive Ti3C2 MXene can significantly separate the charge carriers from ZnO/WO3. On the other hand, this morphology-induced architecture proved sustainable surface interaction with KOH electrolyte than Na2SO3 and Na2SO4 media. Overall, the above developments suggest a robust interface in ZnO/WO3/Ti3C2 under controlled surface morphology and PEC water splitting activity.

Fabrication of magnetic BiOBr/ZnFe2O4/CuO heterojunction for improving the photocatalytic destruction of malachite green dye under LED irradiation: Dual S-scheme mechanism

Constructing superior heterojunction for organic degradation is extremely important but still a big challenge. In this work, a novel magnetic BiOBr/ZnFe2O4/CuO photocatalyst was constructed via a facile hydrothermal approach followed by a co-precipitation method. However, 1D ZnFe2O4 and CuO were uniformly immobilized on the surface of 2D BiOBr nanoplates to develop stable dual S-scheme heterojunction. Significantly, the ternary heterojunction attained optimum photocatalytic properties, in which 98% of malachite green (MG) was destroyed in 90 min. The BiOBr/ZnFe2O4/CuO composite reflected the fastest reaction kinetics of 6.57, 3.78, and 4.31 folds compared to BiOBr, ZnFe2O4, and CuO, respectively. The synergistic action among BiOBr, ZnFe2O4, and CuO exhibited a crucial role in facilitating the charge dissociation in the dual S-scheme route, generating a huge number of reactive species with stronger redox capabilities that can participate in MG elimination. Besides that, the developed heterojunction revealed boosted surface area, which was attributed to the role of BiOBr nanoplates to regulate the deposition of ZnFe2O4 and CuO with lower aggregation effects. Under visible light irradiation, different operational parameters were optimized, such as pH, catalyst loading, and MG concentration. Of note, BiOBr/ZnFe2O4/CuO manifested facile reusability and excellent stability. Dramatically, the scavenger tests indicated significant contributions of •OH, •O2−, h+ in MG destruction over BiOBr/ZnFe2O4/CuO. Finally, the mechanism outcomes clarified that the dual S-scheme system moderates the density of photo-carriers, promoting their migration along suitable pathways.

Highly efficient In2S3 nanosphere decorated WO3/Bi2WO6 dual heterostructure nanoflake arrays for enhanced low bias watersplitting under visible light irradiation

Highly efficient visible light excitation and generating high photogenerated charges in semiconductor electrodes yet challenging in photoelectrochemical (PEC) water splitting. Herein, dual heterojunctions comprising of WO3/Bi2WO6 2D nanoflakes surrounded by In2S3 nanosphere photo absorbers used as a photoelectrodes. Under visible light irradiation, the WO3/Bi2WO6/In2S3 photoelectrode produced an excellent low overpotential-photocurrent. The photocurrent density of 4.02 mA/cm2 at 0.84 V vs. RHE was achieved for a heterostructure photoanode and 8-fold higher than WO3 photoanode. The incident photon to the current conversion efficiency of WO3/Bi2WO6/In2S3 (52% at 400 nm) is about 8 fold higher that of WO3. The improved hydrogen evolution performance was attained through hindering recombination and better band alignment between In2S3 and Bi2WO6. The low charge transfer resistance (152.8 Ohm) of WO3/Bi2WO6/In2S3 photoanode substantially improves the surface charge separation through In2S3 photoactivated catalytic sites. The WO3/Bi2WO6/In2S3 photoanode demonstrates an outstanding charge carriers lifetime, resulting in a maximum photocurrent density of 4.02 mA/cm2 for stable water splitting applications.

Spontaneous Internal Encapsulation via Dual Interfacial Perovskite Heterojunction Enables Highly Efficient and Stable Perovskite Solar Cells

Deep traps stemming from the defects formed at the surfaces and grain boundaries of the perovskite films are the main reasons of nonradiative recombination and material degradation, which significantly affect efficiency and stability of perovskite solar cells (PSCs). Here, a spontaneous internal encapsulation strategy was developed by constructing a dual interfacial perovskite heterojunction at the top and buried interface of the three-dimensional (3D) perovskite film. The spacer cations of the two-dimensional (2D) perovskite structure interacted strongly with the 3D perovskite to passivate the defects and optimize the energy level alignment. Meanwhile, the interfacial perovskite heterojunction underearth delayed the crystallization speed and improved the crystallization quality of the upper 3D perovskite. Thanks to these positive effects, the PSC exhibited a power conversion efficiency of 22.92% with good reproducibility. Significantly, the unencapsulated device with the dual interfacial perovskite heterojunction maintained 88% of its initial efficiency after 2900 h under 65 ± 5% RH in air.

Dual heterojunctions and sulfur vacancies of AgInS2/rGO/MoS2 co-induced photocatalytic degradation of tetracycline hydrochloride

The construction of dual heterojunctions in semiconductors can boost light harvesting, spatial separation of photogenerated electron-hole pairs, as well as photocatalytic efficiency. Sulfur vacancies, as prevalent point defects in semiconductors, can act as active sites for trapping electrons to maneuver charge transfer and separation and surface catalytic reactions. Moreover, the mechanism of synergy of dual heterojunctions and sulfur vacancies co-induced the formation of interfacial electric field should be revealed. In this paper, sulfur vacancies doped AgInS2/rGO/MoS2 dual heterojunctions were prepared via two-step hydrothermal method. Excellent photoelectrochemical performance was achieved on the AgInS2/rGO/MoS2 because sulfur vacancies served as “high-speed electrons trappers”, which may effectively inhibit the recombination of photogenerated charge carriers. Furthermore, the optimal AgInS2/rGO/MoS2, with the molar ratio of AgInS2 and MoS2 equaling 1:1, exhibited high photocatalytic efficiency in removing tetracycline hydrochloride under visible light irradiation. The remarkable photocatalytic activity of AgInS2/rGO/MoS2 can be attributed to the formation of multiple charge transfer pathways between the interfacial layers of Z-scheme heterojunction and rGO-n junction, deriving from the synergistic effect of dual heterojunction and sulfur vacancies. This work offers a promising way into designing dual-heterojunction and intrinsic defect co-induced photocatalysts for removing harmful antibiotic pollutants.

Fabrication of Bi2O3 QDs decorated TiO2/BiOBr dual Z-scheme photocatalysts for efficient degradation of gaseous toluene under visible-light

Weak visible-light capture ability, ultrahigh charge recombination rate, and poor redox ability are crucial constraints to improve the photocatalytic performance for toluene degradation under visible-light. Hence, a dual Z-scheme of Bi2O3 quantum dots decorated TiO2/BiOBr photocatalysts (Bi2O3 QDs@TiO2/BiOBr) were prepared by a two-step hydrothermal method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were performed to identify the existence of Bi2O3 QDs and TiO2 that loaded on the surface of BiOBr. The introducing of oxygen vacancies in TiO2 broadened its light absorption region to the visible-light. The constitutes of Bi2O3 QDs and BiOBr were regulated and the optimized photocatalyst BT1-B10 exhibited 94.1 % of removal rate for gaseous toluene degradation after 150 min irradiation of visible-light (>420 nm) as well as good recoverability and durability. This result was obviously superior to other comparison samples. In-situ DRIFTs spectra and Gas Chromatography-Mass Spectrometry (GC-MS) were carried out to provide a possible pathway for the toluene degradation. Additionally, a dual-channel electron transfer model based on the Z-scheme was proposed, which presented desirable visible-light response region, efficient charge separation efficiency, and enhanced redox ability. Notably, hydroxyl radicals (•OH) served as the dominant active species was confirmed by electron spin resonance (ESR) and gas-phase capture tests, that was beneficial to the ring-opening of toluene degradation. This dual Z-scheme heterojunction of Bi2O3 QDs@TiO2/BiOBr photocatalyst showed great potential for the degradation of toluene under visible-light irradiation.