Formation Of Heterojunction Research Articles

Ultrathin 2D/2D ZnIn2S4/La2Ti2O7 nanosheets with a Z-scheme heterojunction for enhanced photocatalytic hydrogen evolution.

Layered lanthanum titanate (La2Ti2O7) perovskite is a good photocatalytic material owing to its high stability, strong redox ability, and non-toxicity. However, its inherent wide bandgap limits its application in photocatalytic hydrogen evolution. Therefore, combining La2Ti2O7 with two-dimensional (2D) narrow-bandgap semiconductors to form 2D/2D layered structures is the preferred strategy to improve its photocatalytic performance. In this study, a novel 2D/2D ZnIn2S4/La2Ti2O7 Z-scheme heterojunction was prepared through a solvothermal method. The experimental results show that when the molar ratio of La2Ti2O7 to ZnIn2S4 is 1 : 4, the hydrogen evolution rate of the composite under ultraviolet-visible light reaches 6.97 mmol g-1 h-1, which is 3.5 times higher than that of the pure ZnIn2S4. The results of the morphological characterization studies of the samples and the photoelectrochemical measurements show that channels for the rapid transfer of carriers are generated by the unique 2D/2D structure of these samples, and the separation and migration efficiency of the photogenerated carriers significantly improved due to the formation of the Z-scheme heterojunction. This study provides useful insights into the modulation of wide-bandgap semiconductors and research into solar energy conversion.

Synthesis of iron phthalocyanine/CeO2 Z-scheme nanocomposites as efficient photocatalysts for degradation of 2,4-dichlorophenol.

Modulating the photogenerated electrons of CeO2 to activate O2 and efficiently photocatalytic degradation of chlorophenols is a highly desired goal. Herein, we have successfully fabricated an FePc/CeO2 heterojunction through H-bond induced assembly. The photocatalytic degradation of 2,4-DCP by the amount-optimized FePc/CeO2 nanocomposite was improved by 3 times compared with that by pure CeO2. By means of electron paramagnetic resonance (EPR) and single wavelength photocurrent spectroscopy, it is confirmed that the excellent photocatalytic performance is mainly attributed to the formation of the Z-scheme heterojunction, which promotes charge separation and transfer, and the introduction of FePc broadens the visible light absorption range of the heterojunction. Moreover, O2 temperature-programmed-desorbed curves and electrochemical O2 reduction measurement results demonstrate that the single Fe-N4(II) site in FePc is more conducive to promoting O2 activation than that of other metal phthalocyanines. Based on in situ FT-IR and liquid chromatography-tandem mass spectrometry (LC-MS/MS), a possible reaction pathway of 2,4-DCP degradation was proposed. This study provides a novel strategy for preparing CeO2 based Z-scheme heterojunctions with abundant monoatomic sites for pollutant degradation.

Construction of S-scheme heterojunction via Cu2ZnSnS4 coupled with g-C3N4 for enhancing HER performance

It is shown that replacing non-noble metals with noble metals in photocatalytic water splitting is pivotal for increased and sustained hydrogen production. However, the challenge persists in designing and developing a cost-effective, highly active catalyst with effective carrier separation and providing sufficient H+ reduction sites to enhance photocatalytic H2 evolution efficiency. Herein, a series of S-scheme Cu2ZnSnS4/g-C3N4 (CZTS/CN) heterojunction composites were prepared via the hydrothermal method, followed by comprehensive characterizations for in-depth investigation. The TEM image exhibits a clear interface, showing the heterojunction formation between CZTS and CN nanosheets. The results show that incorporating CZTS cocatalyst significantly improves CN photocatalytic hydrogen evolution reaction (HER) and its performance is notably influenced by CZTS to CN mass ratio. Among CZTS/CN heterojunction composites, the 5% CZTS/CN heterojunction composite exhibited a significantly improved HER of 243.64 μmol g−1h−1, which is 29.4 and 7.08 folds superior as compared to CN (8.29 μmol g−1h−1) and CZTS (34.42 μmol g−1h−1), respectively. The mechanism study revealed that the excellent superior H2 evolution performance resulted from the established internal electric field (IEF) in p-n heterojunction, which expedites the efficient separation and migration of photoinduced carriers coupled with the distinctive flower-like configuration of CZTS offering a substantial surface area and enough active reduction sites for photocatalysis process. This work presents a rational design and an inexpensive and efficient heterojunction photocatalysis system suitable for diverse applications.

Optimizing photocatalytic hydrogen evolution performance by rationally constructing S-scheme heterojunction to modulate the D-band center

The research in the field of photocatalysis has progressed, with the development of heterojunctions being recognized as an effective method to improve carrier separation efficiency in light-induced processes. In this particular study, CuCo2S4 particles were attached to a new cubic CdS surface to create an S-scheme heterojunction, thus successfully addressing this issue. Specifically, owing to the higher conduction band and Fermi level of CuCo2S4 compared to CdS, they serve as the foundation and driving force for the formation of an S-scheme heterojunction. Through in-situ X-ray photoelectron spectroscopy and electron paramagnetic resonance analysis, the direction of charge transfer in the composite photocatalyst under light exposure was determined, confirming the charge transfer mechanism of the S-scheme heterojunction. By effectively constructing the S-scheme heterojunction, the d-band center of the composite photocatalyst was adjusted, reducing the energy needed for electron filling in the anti-bonding energy band, promoting the transfer of photogenerated carriers, and ultimately enhancing the photocatalytic hydrogen production. performance. After optimization, the hydrogen evolution activity of the composite photocatalyst CdS-C/CuCo2S4-3 reached 5818.9 μmol g−1h−1, which is 2.6 times higher than that of cubic CdS (2272.3 μmol g−1h−1) and 327.4 times higher than that of CuCo2S4 (17.8 μmol g−1h−1), showcasing exceptional photocatalytic activity. Electron paramagnetic resonance and in situ X-ray photoelectron spectroscopy have established a theoretical basis for designing and constructing S-scheme heterojunctions, offering a viable method for adjusting the D-band center to enhance the performance of photocatalytic hydrogen evolution.

In-situ construction of the novel In2S3/BiOIO3 heterojunction with boosted visible-light photodegradation performance for diverse persistent organic pollutants

Designing rational heterojunctions to achieve efficient separation and transmission of photoinduced charge carriers is one of the effective strategies to improve the activity of semiconductor photocatalysts. In this study, the novel In2S3/BiOIO3 binary heterojunctions were facilely synthesized at room temperature using a simple in-situ growth method. The physicochemical properties of the fabricated In2S3/BiOIO3 heterojunction catalyst were investigated using various techniques including XRD, FT-IR, BET, XPS, TEM, UV–vis DRS, PL, EIS, and PC analysis. The In2S3/BiOIO3 composite catalyst possesses suitable band position and bandgap energy and therefore is capable of degrading organic contaminants under visible light irradiation. The optimized composite catalyst with In2S3/BiOIO3 molar ratio of 0.5 (In2S3/BiOIO3-5) exhibited superior photocatalytic activity, achieving 98.6 % degradation rate for Rhodamine B (RhB), far surpassing the performance of the individual components. In addition, In2S3/BiOIO3-5 showed broad-spectrum photocatalytic activity in the decomposition of various organic pollutants including methyl orange (MO), methylene blue (MB), tetracycline (TC) and bisphenol A (BPA). The improved photocatalytic activity of the prepared composite catalysts can be ascribed to the formation of type-II heterojunction, which facilitates the separation and migration of e–/h+ pairs. The excellent photocatalytic properties and favorable structural stability make In2S3/BiOIO3-5 a viable material for degrading various persistent organic pollutants.

Fabrication of Ag NPs decorated TiO2/WO3 S-scheme heterojunction for efficiently mineralizing gaseous toluene

The energy band structure and corresponding carrier transfer efficiency are crucial roles in photocatalysis performance, especially involving the volatile organic compounds (VOCs) degradation in gas-solid phase photocatalytic systems. Herein, we reported a S-scheme heterojunction photocatalyst of Ag@WO3/TiO2. The photocatalytic experiments display that Ag@WO3/TO2 (denoted as Ag@h-WT) possesses almost 94 % of toluene removal rate and nearly 90 % mineralization after 60 min irradiation under simulated sunlight, superior to those of pure TiO2 and h-WO3 as well as binary WO3/TO2 heterojunction. The improved photocatalytic activity is mainly ascribed to i) the formation of S-scheme heterojunction. ii) The Ag nanoclusters promotes the carrier separation and broadens the light absorption region.

Novel and noble-metal-free CdIn2S4/MoB Schottky heterojunction photocatalysts with efficient charge separation for boosting photocatalytic H2 production

The construction of Schottky heterojunctions by selecting applicable metalloids and semiconductors is highly effective for improving the activity of semiconductors. Herein, we deposited CdIn2S4 on MoB by hydrothermal method to construct a noble metal-free and unreported CdIn2S4/MoB Schottky heterojunction for achieving high photocatalytic H2 production. In ultraviolet photoelectron tests, the Fermi level of the CdIn2S4/MoB composites exhibited a certain shift compared with CdIn2S4 and MoB, manifesting the rearrangement of the Fermi level and the formation of Schottky heterojunction. The formed Schottky heterojunction greatly promoted the electron migration from CdIn2S4 to MoB (proved by XPS tests) to obtain high charge separation efficiency (confirmed by PL and electrochemical tests). CdIn2S4/MoB composites possessed smaller H2 evolution overpotential and Tafel slope, which greatly promoted the release of H2 in the kinetics. Besides, CdIn2S4/MoB composites had higher light absorption capacity and larger specific surface area, which were for more conducive to H2 production. Ultimately, CdIn2S4/MoB composites had significantly improved H2 production activity. Among all composites, the activity of CdIn2S4/20MoB was the highest (463.53 μmol·g−1·h−1), which was 3.5 times that of CdIn2S4-1 %Pt. Besides, CdIn2S4/MoB composites possessed excellent stability in five experiments. Simultaneously, the formation of the Schottky heterojunction and its mechanism of promoting H2 production reaction were also thoroughly investigated. This work is the first to report that MoB could construct Schottky heterojunctions with sulfides for efficient photocatalytic H2 evolution, which is easily extended to sulfides other than CdIn2S4.

Rational design and construction of direct Z-scheme ternary heterojunction photocatalyst AgBr/CoWO4/Ag for efficient environmental remediation

The indiscriminate discharge of micropollutants (e.g., dyes, antibiotics, industrial additives, etc.) represents a significant risk to human health, and the removal of these substances from water bodies has become a prominent area of research within the field of environmental remediation. A simple hydrothermal-precipitation-photoreduction method was employed to synthesize novel Z-scheme heterojunction photocatalysts of AgBr/CoWO4/Ag. The catalysts demonstrated remarkable degradation capabilities with regard to a range of micropollutants present in wastewater. Of the catalysts tested, 5AgBr/CoWO4/Ag exhibited the highest degradation rates, reaching 98.58% for Rhodamine B, 86.82% for tetracycline hydrochloride, and 95.60% for 2-mercaptobenzothiazole within 60 min. In particular, the reaction kinetic rate of 5AgBr/CoWO4/Ag towards Rhodamine B degradation (k2 = 0.26278 L mg−1·min−1) is 9 times that of AgBr (k2 = 0.02953 L mg−1·min−1) and 113 times that of CoWO4 (k2 = 0.00233 L mg−1·min−1), which serves to highlight the exceptional photocatalytic activity of the material. The experimental data and subsequent analysis indicated that the enhanced photocatalytic performance can be attributed to two factors: firstly, the electron mediation by Ag nanoparticles leading to improved charge separation efficiency, and secondly, the formation of Z-scheme heterojunctions between AgBr and CoWO4. The cyclic tests provided confirmation of the excellent stability and recyclability of the AgBr/CoWO4/Ag photocatalysts. It is anticipated that this study will facilitate the development of novel methods for the degradation of refractory micropollutants and provide insights into environmental remediation, thereby contributing to the sustainable development of society.

Design of a novel direct Z-scheme BiOIO3/Bi2WO6 heterojunction for enhanced photocatalytic degradation of norfloxacin under visible light

The unique electronic structure, appropriate bandgap energy, and excellent electron transfer capability make bismuth-based semiconductors hotspots in the field of photocatalysis. Novel BiOIO3/Bi2WO6 Z-scheme heterojunctions were fabricated via in-situ hydrothermal synthesis. The BIOBIW-3 heterojunctions (BiOIO3:Bi2WO6=0.25:0.8, mole ratio) exhibited excellent photocatalytic activity for norfloxacin (NOR), with a degradation efficiency of 90.41 % after 90 min of photoreaction and a reaction kinetic constant of 0.02132 min−1, which was 5.02 and 9.35 times higher than that of BIO and BIW, respectively. The superior photocatalytic performance can be attributed to the intimate interface between BiOIO3 and Bi2WO6, as well as the staggered energy band structure that facilitates the formation of a Z-type heterojunction. This not only widens the range of visible light absorption but also enhances the separation and transfer of photogenerated carriers while maintaining a high capacity for redox reactions. The dominant active species in the degradation process were photogenerated holes (h+) and superoxide (∙O2−) radicals, and an in-depth exploration of the possible mechanism was conducted. Furthermore, the effects of various parameters, including solution pH, catalyst dosage, and NOR concentration on the photocatalytic degradation of NOR were also investigated. The prepared BiOIO3/Bi2WO6 heterojunctions exhibited remarkable photocatalytic performance and chemical stability, presenting a novel research direction for employing layered bismuth-based materials in the degradation of fluoroquinolone antibiotic wastewater.

Z-scheme promoted interfacial charge transfer on Cu/In-porphyrin MOFs/CdIn2S4 heterostructure for efficient photocatalytic H2 evolution

The rational modulation of charge transfer pathway within heterojunction is essential toward boosting photocatalytic activity for H2 production from water splitting Herein, the bimetallic-modified porphyrin MOFs (CuIn-PMOFs) crystals have been developed as a substrate for the epitaxial wrapping of CdIn2S4 (CIS) nanosheets via a facile solvothermal process to fabricate novel hierarchical CuIn-PMOFs@CdIn2S4 (CuIn-PMOFs@CIS) heterojunctions. The experimental results, combined with density-functional theory calculations, demonstrated that the CuIn-PMOFs have a more negative conduction band position and the electrons transfer pathway is inclined from CIS to CuIn-PMOFs, which leads to the formation of unique Z-scheme heterojunctions. Profiting from the special “O-In” charge transfer channel, extensive highly active photoinduced electrons areaggregated and depleted in the conduction band of CuIn-PMOFs, contributing to the improvement of H2 generation activity. Moreover, the heterojunction model also revealed the minimum Gibbs free energy for H* intermediate adsorption (ΔGH*). Concretely, the optimized composite displayed a maximum H2 evolution rate of 7527.54 μmol g–1h−1, which is around 13.12 and 6.63 times higher than that of pure CdIn2S4 and CuIn-PMOFs, respectively. This work aims to suggest that constructing distinctive Z-scheme modulated charge transfer mechanism is an advanced strategy for acquiring highly efficient photocatalysts.

2D/2D Bi2WO6/C3N5 S-scheme heterojunction for highly selective production of CH4 by photocatalytic CO2 reduction under visible light

Photocatalytic CO2 reduction is a practical solution to the energy dilemma and environmental damage caused by greenhouse gases, and it is very important to explore high-efficiency photocatalysts. In this study, a novel Bi2WO6/C3N5 step(S)-scheme heterojunction was successfully constructed and applied for CO2 photoreduction. The 2D/2D structure showed excellent photocatalytic properties, with methane production reaching 1.976 μmol·g−1·h−1 and selectivity reaching 100 % under 5 hours of visible light irradiation. The result indicates that combining Bi2WO6 and C3N5 can promote interfacial charge separation and maintain the optimal reducing ability of photogenerated electrons. Based on experimental and theoretical calculations, we characterized the reaction mechanism and heterojunction formation mechanism. This study offers a novel approach to improve the selectivity and photocatalytic efficiency of CO2 reduction products.

Fabrication of Z-scheme ZnIn2S4/ZnSe heterostructed microspheres toward antibiotic degradation from real pharmaceutical wastewater

BackgroundAlthough Z-type heterojunction can significantly improve the catalytic performance of photocatalyst, there have been few reports on Z-type heterojunction about ZnSe. Therefore, it is meaningful to search for the Z-type photocatalyst in ZnSe to enhance its photocatalytic efficiency. MotivationZnIn2S4, as a novel photocatalyst, its VB (1.72V) and CB (−0.71V) can match with ZnSe, indicating the potential formation of a Z-type heterojunction. Therefore, we hope to construct the ZnIn2S4/ZnSe photocatalyst by forming Z-type heterojunction to boost the photocatalytic activity of ZnSe. MethodsIn this paper, ZnIn2S4/ZnSe heterojunction was prepared through hydrothermal method using ZnIn2S4, Zn(CH3COO)2·2H2O and Na2SeO3 as raw materials, and heated at 180 °C for 24 h. Results and conclusionsThe optimum 30 % ZnIn2S4/ZnSe nanocomposites exhibit superior photocatalytic degradation towards Tc and OTC, with removal rates reaching 80 % and 74 % within 60 min, respectively, significantly higher than the degradation efficiency of pure ZnSe. And in the process of photodegradation for antibiotics, the most significant contribution rate are ∙O2− and h+, while ·OH plays a minor role. Herein, we have provided a good example for removing antibiotic residues by using ZnSe based Z-type heterojunction towards environmental remediation.

Fabrication of ZnO[sbnd]Cu3SnS4 NCs for enhanced visible light-induced photocatalytic degradation of carvedilol

The widespread use of pharmaceutical drugs like carvedilol (CAR) has raised concerns regarding antibiotic resistance, environmental pollution, and potential human health risks. This study addresses these issues by employing advanced pristine nanomaterials, including ZnO and Cu3SnS4 to intricately engineer ZnOCu3SnS4 nanocomposite (NCs). These NCs are designed for enhanced photocatalytic degradation of CAR. Detailed characterization through SEM, and elemental mapping reveals the nanocluster morphology, amorphous nature, proper deposition distribution, and heterojunction formation. XRD studies confirm the purity of the synthesized materials, while XPS validate their chemical states and bonding nature. BET and BHJ analyses demonstrate the enhanced surface area and mesoporous nature of the NCs respectively. UV–visible DRS illustrates successful visible-light sensitization of the ZnOCu3SnS4 NCs with a bandgap of 2.96 eV. Photoluminescence studies indicate reduced charge carrier recombination in the NCs. .OH being the dominant radical involved in photodegradation. The photocatalytic degradation of CAR by ZnOCu3SnS4 NCs achieves a remarkable degradation efficiency of 98 % under optimal condition. These NCs also show outstanding stability across several cycles and remain to function in the presence of ions. Finally, GC–MS analysis suggests the potential CAR degradation routes that result in less hazardous end products. In conclusion, the present research highlights the potential of ZnOCu3SnS4 NCs for efficient wastewater treatment and highlights their capacity to tackle issues related to pharmaceutical drug contamination.

Construction of Z-scheme SbVO4/g-C3N4 heterojunction with efficient photocatalytic degradation performance

As visible light responsive materials, g-C3N4 has become an outstanding research object for photocatalysis due to its facile synthesis, excellent chemical and thermal stability. In this paper, a Z-scheme SbVO4/g-C3N4 heterojunction was successfully constructed by thermal polymerization method. The synthesized SbVO4/g-C3N4 nanocomposite showed efficient photocatalytic activity on tetracycline (TC) degradation. The photocatalytic degradation of TC follows a first-order kinetic model, in which ·O2− and ·OH free radicals play a major role. The formation of Z-scheme heterojunction between SbVO4 and g-C3N4 can effectively promote the separation of photogenerated electron-hole pairs and the generation of ·O2− and ·OH. The photocatalytic removal rate of TC reached 82.3 % within 150 min under visible light. The as-synthesized SbVO4/g-C3N4 heterojunction can still maintain good stability. Furthermore, a photocatalytic degradation mechanism for the SbVO4/g-C3N4 heterojunction is proposed.

A Schottky/Z-Scheme Hybrid for Augmented Photocatalytic H2 and H2O2 Production.

The prodigious employment of fossil fuels to conquer the global energy demand is becoming a dreadful threat to the human society. This predicament is appealing for a potent photocatalyst that can generate alternate energy sources via solar to chemical energy conversion. With this interest, we have fabricated a ternary heterostructure of Ti3C2 nanosheet modified g-C3N4/Bi2O3 (MCNRBO) Z-scheme photocatalyst through self-assembly process. The morphological analysis clearly evidenced the close interfacial interaction between g-C3N4 nanorod, Bi2O3 and Ti3C2 nanosheets. The oxygen vacancy created on Bi2O3 surface, as suggested by XPS and EPR analysis, supported the Z-scheme heterojunction formation between g-C3N4 nanorod and Bi2O3 nanosheets. The collaborative effect of Z-scheme and Schottky junction significantly reduced charge transfer resistance promoting separation efficiency of excitons as indicated from PL and EIS analysis. The potential of MCNRBO towards photocatalytic application was investigated by H2O2 and H2 evolution reaction. A superior photocatalytic H2O2 and H2 production rate for MCNRBO is observed, which are respectively around 5 and 18 folds higher as compared to pristine CNR nanorod. The present work encourages for the development of a noble, eco-benign and immensely efficient dual heterojunction based photocatalyst, which can acts as saviour of human society from energy crisis.

Enhanced photoelectrocatalytic performance of direct Z-scheme CuWO4|TiO2 heterojunction for moxifloxacin oxidation

Films formed by the heterojunction of CuWO4 and TiO2 on conductive transparent substrate (fluorine-doped tin oxide - FTO) were utilized in moxifloxacin (MOX) degradation under polychromatic irradiation. The individual materials and the heterojunctions were systematically characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX), confirming the formation of heterojunctions from pure materials. Compared to the other configuration, the electrochemical characterizations showed higher photocurrent for FTO|CuWO4|TiO2 heterojunction, associated with better charge transport in the film. Thus, the photocatalytic activity of the FTO|CuWO4|TiO2 heterojunction was investigated for MOX degradation, which achieved an oxidation of 54.4 % of the drug in 150 min, employing the configuration electrochemically assisted heterogeneous photocatalysis (EHP). The efficiency of the heterojunction is about 2.5 times greater than that shown by electrodes formed from their individual materials. Radical scavenger studies showed that •OH radicals are the main species responsible for MOX oxidation process. The results of XPS, radical scavenging, photoelectrochemical, and photoelectrocatalytic activity show a charge transfer mechanism associated with a direct Z-scheme and that the FTO|CuWO4|TiO2 film is promising for the degradation of organic pollutants.

Effect of morphology modulation and interface engineering of SnS-MoS2 heterojunction on nonlinear optical response

MoS2 base films with different morphologies were prepared by modulating the magnetron sputtering parameters, and the base films were used to induce the growth of SnS with different structures, forming columnar and worm-like SnS-MoS2 heterojunctions, which were found to have excellent nonlinear absorption properties and their properties could be modulated by the morphology of the films by Z-scanning tests. The tunable morphology and crystalline quality of the films were characterized using scanning electron microscopy, atomic force microscopy and X-ray diffraction techniques and explained using the Stranski-Krastanow growth mechanism. The Raman spectrum of the heterojunction shows the A1g vibrational peak at 320 cm−1 and the appearance of Sn4+ in the X-ray photoelectron spectroscopy confirms the existence of S-Sn-S charge transfer channels between the interfaces. The fine spectra of all the elements in the X-ray photoelectron spectroscopy data as well as the characteristic absorption peaks in the absorption spectra confirm the formation of heterojunctions, and the constructed heterojunctions are determined to be type-II heterojunctions using the method of the core energy level. Heterojunction was determined to be a type-II heterojunction by using the core energy level method. The photoluminescence peak quenching of the heterojunction indicates that there is a process of charge transfer between the interfaces, and the type-II heterostructure of SnS-MoS2 makes the nonlinear absorption performance in the 800 nm band regulated by the morphology of the material. The nonlinear optical absorption coefficient is two orders of magnitude higher than that of the pure materials, and the nonlinear absorption performance of the worm-like SnS-MoS2 heterojunction is superior to that of the columnar SnS-MoS2 heterojunction, which is attributed to the larger interfacial contact area, the better crystalline quality, and the more efficient carrier interfacial transport capability. These tunable type-II SnS-MoS2 heterojunctions with ultrafast nonlinear optical absorption have a positive impact on practical applications such as optical limiter devices and all-optical switching devices.

Origin of the Improved Photoelectrochemical and Photocatalytic Activity in a ZnO-TiO2 Nanohybrid Revealed by Experimental and Density Functional Theory Studies.

Heterojunctions of metal oxides have attracted a great deal of attention as photo (electro) catalysts owing to their excellent photoactivity. While multiple fundamental studies have been dedicated to heteroaggregation, self-assembly of oppositely charged particles to obtain heterojunctions for energy applications has been underexplored. Herein, we report the synthesis of ZnO-TiO2 heterojunctions using the electrostatic self-assembly approach. The synthesized ZnO-TiO2 heterojunctions were characterized by using multiple experimental techniques. Density functional theory calculations were conducted to establish the heterojunction formation mechanism and electronic properties. The ZnO-TiO2 nanohybrid was tested for the photodegradation of rhodamine B dye and water splitting applications. The photocatalytic performance of the ZnO-TiO2 nanohybrid is 3.5 times higher than that of bare ZnO. In addition, the heterostructure exhibited an excellent photocurrent density of 2.4 mA cm-2 at a low onset potential during photoelectrochemical oxygen evolution. The performance improvements are attributed to the formation of the type II heterojunction between ZnO and TiO2, which suppresses carrier recombination and enhances carrier transport, boosting the catalytic activity.

Unraveling the synergism mechanistic insight of O-vacancy and interfacial charge transfer in WO3-x decorated on Ag2CO3/BiOBr for photocatalysis of water pollutants: Based on experimental and density functional theory (DFT) studies

Photocatalysis has been widely used as one of the most promising approaches to remove various pollutants in liquid or gas phases during the last decade. The main emphasis of the study is on the synergy of vacancy engineering and heterojunction formation, two widely used modifying approaches, to significantly alter photocatalytic performance. The vacancy-induced Ag2CO3/BiOBr/WO3-x heterojunction system has been fabricated using a co-precipitation technique to efficiently abate methylene blue (MB) dye and doxycycline (DC) antibiotic. The as-fabricated Ag2CO3/BiOBr/WO3-x heterojunction system displayed improved optoelectronic characteristic features because of the rational combination of dual charge transferal route and defect modulation. The Ag2CO3/BiOBr/WO3-x system possessed 97% and 74% photodegradation efficacy for MB and DC, respectively, with better charge isolation and migration efficacy. The ternary photocatalyst possessed a multi-fold increase in the reaction rate for both MB and DC, i.e., 0.021 and 0.0078 min−1, respectively, compared to pristine counterparts. Additionally, more insightful deductions about the photodegradation routes were made possible by the structural investigations of MB and DC using density functional theory (DFT) simulations. This study advances the understanding of the mechanisms forming visible light active dual Z-scheme heterojunction for effective environmental remediation.

Nonaqueous Synthesis of Pd/PdO-Functionalized NiFe2O4 Nanoparticles Enabled Enhancing n-Butanol Detection.

The efficient detection of n-butanol, which is in demand for highly sensitive materials, is essential for multiple applications. A nonaqueous method was applied to prepare NiFe2O4 nanoparticles (NPs) using benzyl alcohol as a solvent, which shows a size of 7.9 ± 1.6 nm and a large surface area of 82.23 m2/g. To further improve the sensing performance for n-butanol, Pd/PdO functionalization was sensitized with NiFe2O4 NPs. Gas sensing results demonstrate that the Pd/PdO-NiFe2O4 exhibits an enhanced response of 36.9 to 300 ppm n-butanol and a fast response and recovery time (18.2/17.6 s) at 260 °C. Furthermore, the Pd/PdO-NiFe2O4-based sensor possesses a good linear relationship between responses and the n-butanol concentration from 1 to 1000 ppm, and great selectivity against other volatile organic compounds (VOCs). The excellent sensing enhancement is attributed to the catalytic effects of Pd/PdO, the increase of oxygen vacancies, and the formation of heterojunction between PdO and NiFe2O4. Thus, this study offers an effective route for the synthesis of Pd/PdO-functionalized NiFe2O4 NPs to achieve n-butanol detection with excellent sensing performance.