Semiconductor-based Photocatalysts Research Articles

Enhanced Photocatalytic Performances of SnS2/TiO2 Composites via a Charge Separation Following Z-Scheme at the SnS2/TiO2{101} Facets

The formation of heterojunctions for efficient charge separation has been practiced for the preparation of efficient semiconductor-based photocatalysts for applications such as hydrogen production and environmental remediation. In this study, we synthesized a composite structure with a heterojunction between SnS2 and TiO2 through a microwave-assisted hydrothermal process, in which SnS2 nanoparticles grew on nanocrystalline TiO2 nanosheets preferentially at the exposed {101} facets. Appropriate exposure of the {001} and {101} facets of the TiO2 nanosheet in the composite with a preferential growth of SnS2 nanoparticles at the {101} facets was the origin of the charge separation following a direct Z-scheme mechanism to result in enhanced photocatalytic performances in photodegradation of organic dyes such as methylene blue (MB) and rhodamine B (RhB) compared to that of SnS2 and TiO2 alone. A plot of photodegradation rates vs. SnS2 ratios in the composites gave an overall volcano-shaped curve with a maximum at the SnS2 ratio of about 33% at which small SnS2 nanoparticles were populated at the {101} facets of the TiO2 nanosheets with a high surface area (118.2 m2g−1). Our results suggest the microwave-assisted hydrothermal process can be a good synthetic approach for composite-based photocatalysts with a preferential heterojunction structure.

Indium-doped tungsten oxide architectures anchored on 2D rGO Matrix with enhanced visible-light-response and efficient charge separation for photocatalytic degradation of organic pollutants

Visible-light-responsive photocatalysis has been recognized as a sustainable strategy to address environmental pollution, but semiconductor-based photocatalysts often suffer from many shortcomings, including low visible light absorption and rapid recombination of photo-generated charge carriers. In this regard, rationally designed composite materials have gained substantial prominence, as achieving an ideal photocatalyst's characteristics in a single component material is frequently difficult. In the present study, we have synthesized pure (WO3) and indium-doped tungsten oxide (In-WO3) by the facile solvothermal route. The doped material was anchored on a 2D rGO matrix to fabricate the In-WO3/rGO composite. The structural, morphological, electrical, and optical properties of the as-synthesized materials were investigated as a function of doping and composite fabrication by various physical and electrochemical techniques. The comparative photocatalytic performance was evaluated by degrading Congo Red (CR) dye and paracetamol (PCM) drug. The composite material shows degradation efficiencies of ~96% (K=0.0174min-1) and ~91% (K=0.0144min-1) for CR dye and PCM drug, respectively. The boosted catalytic performance corresponds to the declined band gap (2.53eV) and increased conductivity (0.1270 Sm-1), which enhances its visible light absorption and a surge in the charge carrier's population. The kinetics, relative contribution of different active species generated, and the potential mechanism of photodegradation reaction are discussed in detail. The significant increase in photocatalytic performance of the fabricated In-WO3/rGO composite discloses its promising catalytic potential for the degradation of recalcitrant organic pollutants.

Microwave synthesized ternary BiOCl/BiOBr/Bi2O3 nanocomposite for enhanced degradation of organic contaminants under visible light exposure

BackgroundThis research addresses the urgent need for efficient water treatment methods to treat water pollution resulting from industrial activities and population growth. It focuses on developing semiconductor-based photo-catalysts with enhanced photocatalytic activity under visible light, aiming to contribute to pollution control and sustainable energy solutions. MethodsA novel layer-structured ternary BiOCl/BiOBr/Bi2O3 nanocomposite was successfully synthesized via a rapid, one-step microwave-assisted method. The unique layered structure of this heterojunction facilitated efficient migration and separation of photoinduced electron-hole pairs, essential for effective photocatalysis. Significant FindingsThe synthesized nanocomposite exhibited excellent photocatalytic performance, achieving complete degradation of 30 mg L−1 RhB, 98.0% efficiency for 10 mg L−1 TCH, and 83.0% efficiency for 10 mg L−1 MO. Furthermore, the photo-catalyst displayed remarkable photostability, retaining 99.7% efficiency even after seven cycles of RhB degradation. The study also revealed favorable conditions for RhB degradation, emphasizing the impact of high temperature and low pH media while demonstrating the catalyst's resilience to the presence of ions (NO3−, Cl−, SO42−, and NH4+). The study indicates that singlet oxygen (1O2) was predominant among the oxidizing species in photodegradation. This work introduces a highly efficient and stable ternary BiOCl/BiOBr/Bi2O3 nanocomposite as a promising solution for addressing water pollution issues and harnessing visible light for photocatalytic applications.

Enhanced efficiency of AgAlO2/g-C3N4 binary composite to degrade organic pollutants for environmental remediation under visible light irradiation

This study explores the utilization of semiconductor-based photocatalysts for environmental remediation through photocatalytic degradation, harnessing solar energy for effective treatment. The primary focus is on the application of photocatalytic technology for the degradation of 2-chlorophenol and methylene blue, critical pollutants requiring remediation. The research involves the synthesis of binary AgAlO2/g-C3N4 nanocomposites through an exchange ion method, subsequent calcination, and sonication. This process enhances the transfer of photogenerated electrons from AgAlO2 to g-C3N4, resulting in a significantly increased reductive electron charge on the surface of g-C3N4. The photocatalytic activity of the synthesized composites is comprehensively examined in the degradation of 2-chlorophenol and methylene blue through detailed crystallographic, electron-microscopy, photoemission spectroscopy, electrochemical, and spectroscopic characterizations. Among the various composites, AgAlO2/20% g-C3N4 emerges as the most active photocatalyst, achieving an impressive 98% degradation of methylene blue and 97% degradation of 2-chlorophenol under visible light. Notably, AgAlO2/20% g-C3N4 surpasses bare AgAlO2 and bare g-C3N4, exhibiting 1.66 times greater methylene blue degradation and constant rate (k) values of 20.17 × 10−3 min−1, 4.18 × 10−3 min−1 and 3.48 × 10−3 min−1, respectively. The heightened photocatalytic activity is attributed to the diminished recombination rate of electron-hole pairs. Scavenging evaluations confirm that O2•− and h+ are the primary photoactive species steering methylene blue photodegradation over AgAlO2/g-C3N4 in the visible region. These findings present new possibilities for the development of efficient binary photocatalysts for environmental remediation.

Removal of Emerging Organic Pollutants by Zeolite Mineral (Clinoptilolite) Composite Photocatalysts in Drinking Water and Watershed Water

One of the most challenging problems for people around the world is the lack of clean water. In the past few decades, the massive discharge of emerging organic pollutants (EOPs) into natural water bodies has exacerbated this crisis. Considerable research efforts have been devoted to removing these EOPs due to their biotoxicity at low concentrations. Heterogeneous photocatalysis via coupling clay minerals with nanostructured semiconductors has proven to be an economical, efficient, and environmentally friendly technology for the elimination of EOPs in drinking water and watershed water. Natural zeolite minerals (especially clinoptilolites) are regarded as appropriate supports for semiconductor-based photocatalysts due to their characteristics of having a low cost, environmental friendliness, easy availability, co-catalysis, etc. This review summarizes the latest research on clinoptilolites used as supports to prepare binary and ternary metal oxide or sulfide semiconductor-based hybrid photocatalysts. Various preparation methods of the composite photocatalysts and their degradation efficiencies for the target contaminants are introduced. It is found that the good catalytic activity of the composite photocatalyst could be attributed to the synergistic effect of combining the clinoptilolite adsorbent with the semiconductor catalyst in the heterogeneous system, which could endow the composites with an excellent adsorption capacity and produce more e−/h+ pairs under suitable light irradiation. Finally, we highlight the serious threat of EOPs to the ecological environment and propose the current challenges and limitations, before putting the zeolite mineral composite photocatalysts into practice. The present work would provide a theoretical basis and scientific support for the application of zeolite-based photocatalysts for degrading EOPs.

Efficient Photocatalytic Core–Shell Synthesis of Titanate Nanowire/rGO

Wide bandgap semiconductor-based photocatalysts are usually limited by their low solar energy conversion efficiency due to their limited absorption solar wavelength, their rapid surface recombination of the photogenerated electron–hole pairs, and their low charge-carrier mobility. Here, we report a novel stepwise solution synthesis for achieving a new photocatalytic core–shell consisting of a titanate nanowire/reduced graphene oxide shell (or titanate/rGO) 1D-nanocomposite. The new core–shell nanocomposite maximized the specific surface area, largely reduced the charge transfer resistance and reaction energy barrier, and significantly improved the absorption of visible light. The core–shell nanocomposites’ large on/off current ratio and rapid photo-responses boosted the photocurrent by 30.0%, the photocatalysis rate by 50.0%, and the specific surface area by 16.4% when compared with the results for the pure titanate nanowire core. Our numerical simulations support the effective charge separation on the new core–shell nanostructure, which can help further advance the novel photocatalysis.

Photocatalytic CO2 Reduction Using Ti3C2Xy (X = Oxo, OH, F, or Cl) MXene-ZrO2: Structure, Electron Transmission, and the Stability.

CO2 photoreduction using a semiconductor-based photocatalyst is a promising option for completing a new carbon-neutral cycle. The short lifetime of charges generated owing to light energy is one of the most critical problems in further improving the performance of semiconductor-based photocatalysts. This study shows the structure, electron transmission, and stability of Ti3C2Xy (X = oxo, OH, F, or Cl) MXene combined with a ZrO2 photocatalyst. Using H2 as a reductant, the photocatalytic CO formation rate increased by 6.6 times to 4.6 μmol h-1 gcat-1 using MXene (3.0 wt %)-ZrO2 compared to that using ZrO2, and the catalytic route was confirmed using 13CO2 to form 13CO. In clear contrast, using H2O (gas) as a reductant, CH4 was formed as the major product using Ti3C2Xy MXene (5.0 wt %)-ZrO2 at the rate of 3.9 μmol h-1 gcat-1. Using 13CO2 and H2O, 12CH4, 12C2H6, and 12C3H8 were formed besides H212CO, demonstrating that the C source was the partial decomposition and hydrogenation of Ti3C2Xy. Using the atomic force and high-resolution electron microscopies, 1.6 nm thick Ti3C2Xy MXene sheets were observed, suggesting ∼3 stacked layers that are consistent with the Ti-C and Ti···Ti interatomic distances of 0.218 and 0.301 nm, respectively, forming a [Ti6C] octahedral coordination, and the major component as the X ligand was suggested to be F and OH/oxo, with the temperature increasing by 116 K or higher owing to the absorbed light energy, all based on the extended X-ray absorption fine structure analysis.

Crystal Facet Engineering on SrTiO3 Enhances Photocatalytic Overall Water Splitting.

Single-crystal semiconductor-based photocatalysts exposing unique crystallographic facets show promising applications in energy and environmental technologies; however, crystal facet engineering through solid-state synthesis for photocatalytic overall water splitting is still challenging. Herein, we develop a novel crystal facet engineering strategy through solid-state recrystallization to synthesize uniform SrTiO3 single crystals exposing tailored {111} facets. The presynthesized low-crystalline SrTiO3 precursors enable the formation of well-defined single crystals through kinetically improved crystal structure transformation during solid-state recrystallization process. By employing subtle Al3+ ions as surface morphology modulators, the crystal surface orientation can be precisely tuned to a controlled percentage of {111} facets. The photocatalytic overall water splitting activity increases with the exposure percentage of {111} facets. Owing to the outstanding crystallinity and favorable anisotropic surface structure, the SrTiO3 single crystals with 36.6% of {111} facets lead to a 3-fold enhancement of photocatalytic hydrogen evolution rates up to 1.55 mmol·h-1 in a stoichiometric ratio of 2:1 than thermodynamically stable SrTiO3 enclosed with isotropic {100} facets.

Achieving Long-Lived Charge Separated State through Ultrafast Interfacial Hole Transfer in Redox Sites-Isolated CdS Nanorods for Enhanced Photocatalysis.

As opposed to natural photosynthesis, a significant challenge in a semiconductor-based photocatalyst is the limited hole extraction efficiency, which adversely affects solar-to-fuel efficiency. Recent studies have demonstrated that photocatalysts featuring spatially isolated dual catalytic oxidation/reduction sites can yield enhanced hole extraction efficiencies. However, the decay dynamics of excited states in such photocatalysts have not been explored. Here a ternary barbell-shaped CdS/MoS2/Cu2S heterostructure is prepared, comprising CdS nanorods (NRs) interfaced with MoS2 nanosheets at both ends and Cu2S nanoparticles on the sidewall. By using transient absorption (TA) spectra, highly efficient charge separation within the CdS/MoS2/Cu2S heterostructure are identified. This is achieved through directed electron transfer to the MoS2 tips at a rate constant of >8.3 × 109 s-1 and rapid hole transfer to the Cu2S nanoparticles on the sidewall at a rate of >6.1 × 1010 s-1, leading to an exceptional overall charge transfer constant of 2.3 × 1011 s-1 in CdS/MoS2/Cu2S. The enhanced hole transfer efficiency results in a remarkably prolonged charge-separated state, facilitating efficient electron accumulation within the MoS2 tips. Consequently, the ternary CdS/MoS2/Cu2S heterostructure demonstrates a 22-fold enhancement in visible-light-driven H2 generation compare to pure CdS nanorods. This work highlights the significance of efficient hole extraction in enhancing the solar-to-H2 performance of semiconductor-based heterostructure.

Progress on enhancing the charge separation efficiency of carbon nitride for robust photocatalytic H2 production.

Solar-driven H2 production from water splitting with efficient photocatalysts is a sustainable strategy to meet the clean energy demand and alleviate the approaching environmental issues caused by fossil fuel consumption. Among various semiconductor-based photocatalysts, graphitic carbon nitride (g-C3N4) has attracted much attention due to its advantages of long term-stability, visible light response, low cost, and easy preparation. However, the intrinsic Coulombic attraction between charge carriers and the interlayer electrostatic barrier of bulk g-C3N4 result in severe charge recombination and low charge separation efficiency. This perspective summarizes the recent progress in the development of g-C3N4 photocatalytic systems, and focuses on three main modification strategies for promoting charge transfer and minimizing charge recombination, including structural modulation, heterojunction construction, and cocatalyst loading. Based on this progress, we provide conclusions regarding the current challenges of further improving photocatalytic efficiency to fulfill commercial requirements, and propose some recommendations for the design of novel and satisfactory g-C3N4 photocatalysts, which is expected to progress the solar-to-hydrogen conversion.

Sonochemical regulation of oxygen vacancies for Bi2WO6 nanosheet-based photoanodes to promote photoelectrochemical performance.

Integration of oxygen vacancies (Vo) into nanostructured semiconductor-based photocatalysts has been recognized as a promising strategy for enhancing the performance of photoelectrochemical (PEC) water splitting. However, precisely controlling the Vo concentration in photocatalysts via an effective and tunable approach remains challenging. Herein, a series of optimized bismuth tungstate (Bi2WO6) nanosheet-based photoanodes with varying concentrations of Vo were prepared by a sonochemical method with in situ cavitation detection, which enables accurate manipulation of the acoustic cavitation intensity applied to the surface of Bi2WO6 photoanodes in alkaline solution. Based on the analysis of the Vo concentration and sound field characteristics, the mechanism of sonochemical regulation of Vo in Bi2WO6 nanosheets was interpreted. Specifically, the increase in Vo concentration can be attributed to the enhancement of Bi-O bond dissociation. This enhancement is influenced not only by the intensified impact of shear force and the generation of active radicals by transient cavitation, but also by the accelerated diffusion of the reactant, a result of stable cavitation. By optimizing the transient and stable cavitation intensity, a Vo-rich Bi2WO6 photoanode was obtained without altering the microstructure of Bi2WO6 nanosheets. The presence of high concentration Vo facilitates the interfacial chemical reactivity and the transmission of photogenerated carriers, leading to the drastic promotion of the PEC water splitting performance. The transient photocurrent density of the Vo-rich Bi2WO6 photoanode reaches 69.2 μA cm-2 (1.23 V vs. RHE), 7.86 times that of the untreated Bi2WO6 photoanode. Additionally, the charge injection efficiency increases to 35.4%. This work provides a controllable and effective method for defect engineering of nanostructured semiconductor-based electrodes.

Carbon nanofibers (CNf) cocatalyst-integrated CdS nanoflowers photocatalyst for the deterioration of rhodamine B

In a heterostructure photocatalyst, a proper co-catalyst plays an important role, which is essential for achieving high efficiency in photocatalyst systems for treating organic pollutants. Carbonaceous nanomaterials are recognized as the most effective, economical, and environmentally friendly cocatalyst for various semiconductor-based heterostructure photocatalysts. CNf would be the best carbonaceous semiconducting material to form a heterogeneous photocatalyst. The heterostructure of CNf/CdS nanoflowers is prepared by a solvothermal route and probed for visible-light decomposition of the rhodamine B (RhB) dye. CNf provides a large surface area for dye adsorption, acts as a sink for photogenerated electrons from the semiconductor CdS, and improves the utilization of visible light. As a result, CNf as a co-catalyst significantly improved the photocatalytic performance of semiconductor-based organic pollutant removal systems. The plausible degradation mechanism of RhB is determined on the basis of the scavenger study. The intermediates formed during photodegradation were detected by LCMS analysis. The probable pathway of RhB degradation to CO2 and H2O is presented in this report.

CaTiO3 perovskite /g-C3N4 heterojunction-based composite photocatalyst, part II: Synthesis, characterization and the boosted photocatalytic activity towards Gemifloxacin

BackgroundDue to the potential ecosystem protection and management applications, searching to achieve highly optimized semiconductor-based photocatalysts utilizing solar energy is still a significant challenge. MethodsThus, CaTiO3/g-C3N4 heterostructures synthesis via in-situ calcination method was synthesized here, and its structure was investigated by different characterization techniques such as FT-IR, XRD, SEM, EDX, X-ray mapping, cyclic voltammetry (CV), EIS, and DRS techniques. Significant findingsThe average crystallite size of the composite sample was estimated at 3.8 nm and 3.5 nm, respectively, according to the Scherrer and Williamson-Hall using XRD results. pHpzc values were approximately 8.6, 5.5, and 6.5 for CaTiO3, g-C3N4, and CaTiO3/g-C3N4 samples. Based on the DRS data, the evaluated band gap energy for the g-C3N4, CaTiO3, and CaTiO3/g-C3N4 were 2.76, 3.5, and 2.6 eV, respectively. EIS and CV data confirmed better charge carriers' transfer in the composite. The proposed CaTiO3/g-C3N4 composite showed a synergistic effect in the photodegradation of Gemifloxacin in an aqueous solution under both UV and Vis light illumination. Changes in the CaTiO3:g-C3N4 ratio varied the photocatalytic activity of the obtained catalyst.

Comparative photocatalytic study of visible light driven BiVO4, Cu2O, and Cu2O/BiVO4 nanocomposite for degradation of antibiotic for wastewater treatment.

Semiconductor-based photocatalysts have become increasingly used in the removal of pollutants from wastewater, especially antibiotics. A series of composite-based cuprous oxide and bismuth vanadate (Cu2O/BiVO4) composite-based photocatalysts were synthesized by using the chemical method. The structure of the Cu2O/BiVO4 composite was verified by using x-ray diffraction, scanning electron microscopy, photoluminescence, Fourier transform infrared spectroscopy, and UV-visible spectra. The degradation of methylene blue (MB) and tetracycline (TC) was investigated to check the photocatalytic activity of the Cu2O/BiVO4 composite series. The quantity of Cu2O was varied from 1% to 7% by weight to prepare the series of Cu2O/BiVO4 composites. The analysis of results verified that 5% Cu2O/BiVO4 exhibits an outstanding photocatalytic activity as compared to 1%, 3%, and 7% Cu2O/BiVO4, pure Cu2O, and pure BiVO4 under visible light irradiation. The optimum value of photocatalytic degradation achieved with 5% Cu2O/BiVO4 was 97% for MB dye and 95% for TC in 120min, which is greater than the photocatalytic degradation of pure BiVO4 (MB 45% and TC 72%), pure Cu2O (MB 57% and TC 80%), 1% Cu2O/BiVO4 (MB 72% and TC 85%), 3% Cu2O/BiVO4 (MB 83% and TC 88%), and 7% Cu2O/BiVO4 (MB 87% and TC 91%). The stability and reusability of Cu2O/BiVO4 were also investigated. To check the major role of trapping in degradation, a trapping experiment was also performed by using three trapping agents: BQ, EDTA, and tBuOH. The results showed that Cu2O/BiVO4 exhibits an improved photocatalytic activity in the degradation of antibiotics in polluted water because the recombination rate of the electron-hole pair decreased and the surface area increased, which increased the active sites for redox reactions. Such a photocatalytic composite with high efficiency has various applications, such as energy production, environmental remediation, and water remediation.

Machine learning analysis to interpret the effect of the photocatalytic reaction rate constant (k) of semiconductor-based photocatalysts on dye removal

Photocatalytic reactions with semiconductor-based photocatalysts have been investigated extensively for application to wastewater treatment, especially dye degradation, yet the interactions between different process parameters have rarely been reported due to their complicated reaction mechanisms. Hence, this study aims to discern the impact of each factor, and each interaction between multiple factors on reaction rate constant (k) using a decision tree model. The dyes selected as target pollutants were indigo and malachite green, and 5 different semiconductor-based photocatalysts with 17 different compositions were tested, which generated 34 input features and 1527 data points. The Boruta Shapley Additive exPlanations (SHAP) feature selection for the 34 inputs found that 11 inputs were significantly important. The decision tree model exhibited for 11 input features with an R2 value of 0.94. The SHAP feature importance analysis suggested that photocatalytic experimental conditions, with an importance of 59%, was the most important input category, followed by atomic composition (39%) and physicochemical properties (2%). Additionally, the effects on k of the synergy between the metal cocatalysts and important experimental conditions were confirmed by two feature SHAP dependence plots, regardless of importance order. This work provides insight into the single and multiple factors that affect reaction rate and mechanism.

Construction of oxygen-deficient In2O3/ZnIn2S4 with hollow tubular heterostructure for photocatalytic CO2 reduction to syngas and benzyl alcohol oxidation

To reduce the recombination of the photogenerated charge carriers (PCCs), increase the utilization of the PCCs may be an effective method. In this work, the heterojunction catalysts of MIL-68 derived In2O3 (IO) microtube and ZnIn2S4 (ZIS) nanosheets were prepared by self-template and in-situ growth strategy. By growing ZnIn2S4 nanosheets on the surface of oxygen-deficient IO microtube, these two distinct semiconductors are integrated into hierarchical tubular hybrids with heterogeneous interfacial contacts. To improve the utilization rate of PCCs, the photocatalytic CO2 reduction is proceeded on IO/ZIS composite coupling with benzyl alcohol (PhCH2OH) oxidation. With the mass ratio of IO and ZIS adjusted, 30% IO/ZIS performs the best photocatalytic activity of CO2 reduction, which is 64.19 times higher than that of pure ZIS. The largely enhanced photocatalytic activity of IO/ZIS is attributed to the intimate interfacial contacts between IO and ZIS, which accelerates the separation and migration of PCCs via the Z-scheme model. The separated electrons and holes are respectively participated in the CO2 reduction and the PhCH2OH oxidation, as the reduction and oxidation products are close to 1: 1. This work not only provides the guideline for the design and construction of complex semiconductor-based photocatalysts, but an effective way to increase the utilization of PCCs.

V2C MXene–modified g-C3N4 for enhanced visible-light photocatalytic activity

Increasing the efficiency of charge transfer and separation efficiency of photogenerated carriers are still the main challenges in the field of semiconductor-based photocatalysts. Herein, we synthesized g-C3N4@V2C MXene photocatalyst by modifying g-C3N4 using V2C MXene. The prepared photocatalyst exhibited outstanding photocatalytic performance under visible light. The degradation efficiency of methyl orange by g-C3N4@V2C MXene photocatalyst was as high as 94.5%, which is 1.56 times higher than that by g-C3N4. This was attributed to the V2C MXene inhibiting the rapid recombination of photogenerated carriers and facilitating rapid transfer of photogenerated electrons (e−) from g-C3N4 to MXene. Moreover, g-C3N4@V2C MXene photocatalyst showed good cycling stability. The photocatalytic performance was higher than 85% after three cycles. Experiments to capture free radicals revealed that superoxide radicals (·O2−) are the main contributors to the photocatalytic activity. Thus, the proposed g-C3N4@V2C MXene photocatalyst is a promising visible-light catalyst.

Coupling of surface oxygen vacancy and 2D structure of Aurivillius-phase CaBi2Ta2O9 nanoplates for enhanced photocatalytic H2 production

Solar-driven water splitting over semiconductor-based photocatalyst is considered as one of the most promising approaches to address the looming energy shortage and environmental pollution. However, most of photocatalysts still suffer from low hydrogen production activity owing to the poor photo-absorption ability, rapid recombination of photo-generated charge carriers and insufficient surface active sites. Herein, we tackle these challenges by introducing surface oxygen vacancies (OVs) on the layered Aurivillius-phase perovskite CaBi2Ta2O9 nanoplates via a combined high-temperature molten salt and post-reduction process. Theoretical and experimental results demonstrate that the rich OVs anchored on the surface of CaBi2Ta2O9 nanoplates not only extend the photo-responsive range to visible region, improve the separation efficiency of photo-induced charge carriers, but also enrich the surface reactive sites. As a result, under a 300 W xenon lamp irradiation, the OVs-abundant CaBi2Ta2O9 nanoplates exhibit an outstanding H2 production rate, which is 7.4 times higher than that of the bulk CaBi2Ta2O9 in the absence of OVs. Our study provides a general and efficient coupling strategy to advance the H2 production performance of layered perovskite oxide for solar energy conversion.

Principle of CoS2/ZnIn2S4 heterostructure effect and its mechanism of action in a visible light-catalyzed antibacterial process

The development of visible-light-driven catalytic antimicrobial technology is a significant challenge. In this study, heterojunctions were constructed for the appropriate modification of semiconductor-based photocatalysts. A simple hydrothermal method was used for material reconstruction, and smaller CoS2 nanoparticles were deposited and in situ grown on two-dimensional nanoflower-like ZnIn2S4 carriers to form CoS2/ZnIn2S4 (CS/ZIS) Schottky heterojunctions. Systematic study via characterization techniques and density functional theory calculations indicated that the excellent photocatalytic activity of CS/ZIS stemmed from the solid interfacial coupling between the two solid-phase materials. These materials acted as co-catalysts to increase the number of active reaction sites, enhance charge transfer, drive unidirectional electron movement, and improve charge separation efficiency, which effectively facilitated the production of reactive oxygen species (ROS). The optimized CS/ZIS heterojunction exhibited excellent performance for the efficient photocatalytic degradation of organic matter and inactivation of Escherichia coli (E. coli) compared with the ZnIn2S4 photocatalyst. Moreover, the antibacterial mechanism of the heterojunction photocatalyst and the extent of damage to the cell membrane and internal cytoplasm were explored by performing various assays. It was demonstrated that superoxide radicals are the predominant active species and multiple ROS act together to cause oxidative stress damage and cell inactivation.

Enhancing photocatalytic degradation efficiency via the construction of organic/inorganic S-scheme supramolecular hybrid heterostructures

This study demonstrates the successful construction of a hybrid van der Waals heterostructure (vdWH) consisting of 3D supramolecular networks and 2D semiconductor Ag3PO4, using hydrogen-bonded 3D networks H12SubPcB-OPh2OH self-assembled onto Ag3PO4. The resulting organic/inorganic vdWH exhibits significantly enhanced photocatalytic degradation efficiency for oxytetracycline (OTC) and tetracycline (TC) under visible light irradiation, with apparent rate constants 1.8 and 1.5 times higher than those of pristine Ag3PO4, respectively. Moreover, after five photocatalytic cycles, the photocatalytic activity of vdWH was still much higher than that of pristine Ag3PO4. Molecular dynamics simulations indicate that the SubPc-3 supramolecular assembly is more prone to forming a 3D hydrogen bonding network rather than a 1D columnar stacking. In-situ irradiated X-ray photoelectron spectroscopy analyses and theoretical calculations confirm that the charge transfers between H12SubPcB-OPh2OH and Ag3PO4 are consistent with the S-scheme mechanism. This work provides a promising strategy for designing and fabricating efficient and stable supramolecular self-assembled semiconductor-based photocatalysts.