Binary Photocatalysts Research Articles

Enhanced visible light photocatalytic degradation of bisphenol A (BPA) by reduced graphene oxide (RGO)–metal oxide (TiO2, ZnO and WO3) based nanocomposites

We have successfully synthesized high-performance visible light photocatalytic activity of Reduced graphene oxide (rGO) and metal oxide dependent binary (RGO/TiO2, RGO/ZnO, and RGO/WO3) nanocomposites (NCs) with improved adsorption characteristics using hydrothermal method. The titanium oxide (TiO2), zinc oxide (ZnO), and titanium oxide (WO3) are strongly anchored over RGO nanosheets in the microscopy images of the nanocomposites, which increases the surface area of the resulting NCs. The UV and PL findings show that combining RGO with metal oxides could increase the charger transfer process and organic pollutant absorption significantly. With varying irradiation times, the photodegradation of methylene blue (MB) and bisphenol A (BPA) contaminants was recorded under visible light (0–60 min). As compared to other binary photocatalysts, the RGO/TiO2 composite photocatalyst delivers a high photodegradation (98.5%), first order kinetic rate constant (0.9 × 10−3 min−1) and long lasting stability against BPA. The synthesis of the samples with outstanding properties collected herein has the potential to greatly extend the application possibilities for environmental energy system applications.

Double Z-scheme FeVO4/Bi4O5Br2/BiOBr ternary heterojunction photocatalyst for simultaneous photocatalytic removal of hexavalent chromium and rhodamine B

HypothesisFabrication of the heterojunction photocatalyst with appropriate band potentials as a promising method of inhibiting electron-hole pair recombination leading to enhanced photocatalytic properties. ExperimentsHerein, BiOBr, Bi4O5Br2, and binary BiOBr/Bi4O5Br2 composite were selectively synthesized by employing a one-step microwave irradiation method. Then, double Z-scheme FeVO4/Bi4O5Br2/BiOBr ternary composites with different weight percentages (%wt) of FeVO4 were fabricated and their photocatalytic applications were studied. The photodegradation of organic compounds (rhodamine B (RhB), methylene blue (MB) and salicylic acid (SA)), along with the photoreduction of hexavalent chromium (Cr(VI)) were investigated. FindingsComparing with the single and binary photocatalysts, and a commercial TiO2, the 1 %wt-FeVO4/Bi4O5Br2/BiOBr photocatalyst demonstrated superior visible-light-driven photocatalytic performance. In a Cr(VI)/RhB combined system, Cr(VI) photoreduction was further improved and coexisting RhB molecules were simultaneously degraded. Removal of Cr(VI) and RhB were maximized by adjusting both pH values and catalyst dosages. Based on UV–vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, electrochemical investigations, active-species trapping, nitrotetrazolium blue transformation, and silver photo-deposition experiments, a double Z-scheme charge transfer mechanism with an RhB-sensitized effect was proposed. This special mechanism has led to significant enhancement in charge segregation and migration, along with higher redox properties of the ternary composite, which were responsible for the excellent photocatalytic activity.

Construction of Z-scheme g-C3N4 / MnO2 /GO ternary photocatalyst with enhanced photodegradation ability of tetracycline hydrochloride under visible light radiation

A facile wet-chemical method was adopted to synthesize g-C3N4/MnO2/GO heterojunction photocatalyst for visible-light photodegradation of tetracycline hydrochloride (TC). The addition of MnO2 and GO increased the absorption of visible light and the specific surface area of the photocatalyst. The results of photoluminescence, electrochemical impedance spectroscopy, and photocurrent response indicated that CMG-10 had the lowest electron–hole recombination probability, which was beneficial for the photocatalytic reaction. The ternary photocatalyst exhibited enhanced photoelectric performance and superior photocatalytic activity with 91.4% removal of TC (10 mg/L) under a mere 60 min visible light illumination, which showed enhanced photocatalytic degradation when compared with binary (CM, 77.95%; CG, 78.83%) and single (C3N4, 55.5%; MnO2, 36.41%) photocatalysts. A pH of 6 was optimal for the CMG-10 photocatalytic degradation of TC, and the optimal photocatalyst dosage was 0.5 g/L. Common coexisting ions influenced the removal of TC by influencing the production of active species. The catalyst is stable and reusable with only a 10% reduction in removal efficiency after four cycles. According to the active species analysis, the Z-scheme mechanism was a charge transfer behavior in the composite photocatalyst, which could prevent the recombination of photogenerated carriers. This study presents a photocatalytic approach to the effective removal of TC from water bodies, which provides practical implications to advance the use of photocatalytic technology in the restoration of aqueous environmental pollution.

Construction of visible-light driven Bi2MoO6-rGO-TiO2 photocatalyst for effective ofloxacin degradation

Photocatalytic removal is more appropriate for the destruction of organic contaminants. The ternary Bi2MoO6-reduced graphene oxide (rGO)-TiO2 catalyst was synthesized using a simple hydrothermal method, and various surface analytical optical techniques were analyzed. The photocatalytic decomposition efficiency of the Bi2MoO6-rGO-TiO2 composite was 92.3% higher than those of pure and binary photocatalysts. The effects of operational parameters, such as catalyst ratio, catalyst variation, rGO ratio variation, and pH value variation were also analyzed. The as-prepared ternary photocatalyst exhibited low photoluminescence and high photocurrent density, which suppressed photon-induced electron and hole (h+) recombination and effective charge separation. The study demonstrated that rGO has excellent electron transfer performance and enhanced photocatalytic reaction stability. The perfect cycling stability of Bi2MoO6-rGO-TiO2 was retained even after five consecutive cycles on the photocatalytic degradation reaction performance. In this study, we propose a decomposition performance mechanism for ofloxacin degradation that underwent visible-light irradiation.

A novel noble-metal-free binary and ternary In2S3 photocatalyst with WC and “W-Mo auxiliary pairs” for highly-efficient visible-light hydrogen evolution

Herein, noble-metal-free In2S3-WC and In2S3-based photocatalysts with dual cocatalysts of flower-like MoS2 and bulk WC were synthesized through a facile solvothermal reaction. Electrochemical results indicated WC increased the interface conductance of photocatalyst and boosted the transference of photogenerated carriers. The optimal In2S3-WC show a hydrogen production rate of 128.11 μmol·h−1·g−1, which is around 6 times higher than In2S3-1%Pt (20.73 μmol·h−1·g−1). The above results demonstrate commercial WC has a crucial impact of replacing precious metal and separating carriers. Morphology characterization exhibited hydrangea In2S3 and flower-like MoS2 were attached to bulk WC. Gratifyingly, photocurrent, impedance and photoluminescence results demonstrated MoS2 further effectively separated the photogenerated carriers. Remarkably, the higher hydrogen generation rate of 390.52 μmol·h−1·g−1 obtained by the optimal ternary In2S3-WC-MoS2 composite was around 3 and 18 times higher than the optimal In2S3-WC and In2S3-1% Pt. The photocatalytic results demonstrated that "W-Mo auxiliary pairs" was a great efficient synergistic cocatalyst for In2S3 to increase active sites and improve e--h+ pairs separation for H2 generation. Furthermore, a probable reaction mechanism of the enhanced photocatalytic H2 generation was also proposed. This presented research provides an effective concept to design novel and efficient noble-metal-free photocatalyst with "W-Mo auxiliary pairs" for prominent H2 generation activity.

CeO2 nanoparticles dispersed on CoAl-LDH hexagonal nanosheets as 0D/2D binary composite for enhanced photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution is considered a sustainable and environmentally friendly strategy to solve the increasingly serious environmental and energy crisis. A reasonable construction of heterojunction is a common method to improve the performance of photocatalysts. A novel binary composite photocatalyst was synthesized by modifying two-dimensional (2D) layered CoAl-LDH with zero-dimensional (0D) CeO2 nanoparticles for the first time. CeO2 has a lower reduction potential, and the cross band structure of the two semiconductors makes the electrons on the conduction band of CoAl-LDH spontaneously transfer to the CeO2, the electron transfer between them significantly reduces the recombination rate of photogenerated carriers, thus improved the hydrogen production efficiency. In addition, photoelectrochemical experiments show that the composite has the stronger visible light response, lower hydrogen evolution overpotential and interfacial transfer resistance, implying predominant photocatalytic hydrogen evolution performance, and stability of the composite photocatalyst. This study provides a new strategy for the application of CoAl-LDH in photocatalytic hydrogen production.

Visible-light driven S-scheme Mn0.2Cd0.8S/CoTiO3 heterojunction for photocatalytic hydrogen evolution

A novel S-scheme Mn0.2Cd0.8S/CoTiO3 photocatalytic system was formed. The morphology, microstructure, chemical state and optical behavior of Mn0.2Cd0.8S/CoTiO3 have been studied using SEM, XRD, TEM, UV–vis, PL and TRPL techniques, which proves that the existence of the S-scheme heterojunction accelerates the transfer of photogenerated carriers and the ability to capture and utilize visible light. The electrochemical test proved that the composite sample greatly reduces the overpotential of the hydrogen evolution reaction, thereby achieving ultra-high hydrogen evolution. In addition, the feasible mechanism of photocatalytic hydrogen evolution is described. This work will furnish fresh insights for the conception and construction of efficient binary heterojunction photocatalysts.

A Ternary Photocatalyst with Double Heterojunctionsfor Efficient Diesel Oil Degradation

AbstractThe photodegradation is a potential technology to solve environmental issues such as the diesel oil pollution. The titanium dioxide/graphitic carbon nitride (TiO2/g‐C3N4) photocatalyst is widely used for the photodegradation of pollutants. However, the performances of this binary photocatalyst such as the degradation efficiency and cyclic stability are still unsatisfactory for real applications. In our work, we introduce a p‐type NiO semiconductor into the binary TiO2/g‐C3N4 (98: 2) photocatalyst by a simple dipping method. The NiO semiconductor can form double heterojunctions with the TiO2 and g‐C3N4 (dual Z‐scheme and Z‐scheme+p‐n), which can accelerate the separation of photo‐generated electron‐hole pairs effectively. Thus, the as‐obtained ternary TiO2/NiO/g‐C3N4 (TCN) sample delivers a good photocatalytic performance for diesel oil degradation under a simulated sunlight. Specifically, the TCN (7 : 3) photocatalyst exhibits a 98.94 % degradation efficiency after 2 h of visible‐light, largely outperforming the single‐component photocatalysts (TiO2, g‐C3N4, NiO,) and the binary TiO2/g‐C3N4 (98 : 2) photocatalyst. The free radical capture test manifests that is the major factor on the degradation. This work presents a typical example to boost the photodegradation performance via a ternary catalyst design, which will provide valuable insight for the future high‐performance diesel oil degradation.

TiO2 doped HKUST-1/CM film in the three-phase photocatalytic ammonia synthesis system

Photocatalytic synthesis of ammonia from N2 and H2O at room temperature and atmospheric pressure is considered to be a safe, clean and sustainable method. Due to the low solubility and diffusion coefficient of nitrogen in water, the rate of ammonia synthesis is significantly hindered. As a result, we develop a kind of thin film photocatalyst, which can be used in gas-liquid-solid three phase reaction system to solve this problem. The catalyst bases on HKUST-1 thin film with high nitrogen adsorption performance and supported with TiO2 nanoparticles with photocatalytic nitrogen fixation performance. The constructed binary composite photocatalyst has a stable structure under a 300 W xenon lamp, which exhibits good photoelectric conversion performance. While characterizing the structure and photoelectric performance of the material, the performance of photocatalytic ammonia synthesis was investigated. The highest ammonia synthesis efficiency was 0.048 μmol·h−1·cm−2, and its performance was 2.8 times that of TiO2/CM catalyst under the same conditions. The thin film catalyst does't contain any N substance and won't interfere with the ammonia synthesis reaction. The preparation process is simplified by directly using the copper source in the CM without additional metal reagent. Moreover, it provides a new idea for the design of photocatalytic catalysts for ammonia synthesis.

Integration of Bi5O7I with TiO2: Binary photocatalysts with boosted visible-light photocatalysis in removal of organic contaminants

The water pollution caused by releasing widespread organic dyes into wastewater is one of the most important concerns affecting the human life. Providing visible-light-responsive photocatalysts based on TiO2 can be noticed as a promising approach for the remedy of water contaminations. Herein, Bi5O7I nanoparticles were integrated with TiO2 to establish efficient TiO2/Bi5O7I heterojunction photocatalysts with the aid of hydrothermal method. Several complementary analyses of XRD, SEM, EDS, BET, photocurrent density, UV–vis DRS, TEM, HRTEM, PL, EIS, and XPS were applied to investigate the structure, texture, optical feature, and charge transfer efficiency of the as-prepared photocatalysts. The obtained results of the mentioned analyses revealed that the Bi5O7I particles have been successfully introduced to the surface of TiO2. The photocatalytic property of TiO2/Bi5O7I nanocomposites was evaluated by the elimination of fuchsine, MB, MO, and RhB pollutants under visible light. According to the photocatalytic tests, the binary photocatalysts manifested a prominent ability in the degradation of these pollutants than the single components. The outstanding photocatalytic ability belonged to the TiO2/Bi5O7I (15%) sample. The photocatalytic performance of TiO2/Bi5O7I (15%) was 3.8, 4.1, 3.6, and 15.1 times more than Bi5O7I and 16.8, 14.8, 18.4, and 50.5 times premier than TiO2 in the elimination of MB, fuchsine, MO, and RhB contaminants, respectively. The charge separation efficiency of the electron-hole pairs in TiO2/Bi5O7I photocatalysts was confirmed by photoelectrochemical tests. The increased surface area, boosted visible-light absorption, as well as extended lifetime of photogenerated charges have led to enhanced photocatalytic efficiency in the TiO2/Bi5O7I nanocomposites. Based on the radical trapping tests, the h+ and •O2− identified as the active species in the degradation reaction. A possible photocatalytic mechanism and photo-degradation pathway were proposed based on the outcomes obtained from the trapping experiments and photoelectrochemical analysis. Moreover, the TiO2/Bi5O7I samples exhibited good photostability over four cycles. This work presented that the TiO2/Bi5O7I photocatalysts can be a proper candidate for environmental purification.

Fabrication of a Z-Scheme Heterojunction Polyhedral-Shaped BiOIO3/MIL-53(Fe) Photocatalyst for Enhancing Gaseous Hg0 Removal

A Z-scheme heterojunction polyhedral-shaped BiOIO3/MIL-53(Fe) photocatalyst is prepared by a solvothermal method. The samples are characterized by XRD, XPS, SEM, TEM, FT-IR, UV–vis, PL, and other material characterization analysis methods. The photocatalytic performance of photocatalysts is studied for removal of vapor-phase mercury (Hg0) under visible-light irradiation. The results suggest that the Hg0 removal efficiency of the BiOIO3/MIL-53(Fe) composite is significantly improved compared with that of MIL-53(Fe). When the molar ratio of BiOIO3 and MIL-53(Fe) is 2:1, the BiOIO3/MIL-53(Fe) composite photocatalyst exhibits the best Hg0 removal efficiency, reaching 74.19%. BiOIO3 and MIL-53(Fe) form a Z-scheme heterojunction with a suitable energy band structure, which results in the effective separation of photoinduced electron–hole pairs and delays their recombination. Finally, the photocatalytic oxidation mechanism of Hg0 by the BiOIO3/MIL-53(Fe) composite is proposed, which paves the way for the study of the built-in electric field and electron transport channels between binary photocatalyst materials.

Persulfate enhanced visible light photocatalytic degradation of iohexol by surface-loaded perylene diimide/acidified biochar

Persulfate (PS) is extensively employed as an oxidant to develop the sulfate radical-based advanced oxidation processes for removing organic pollutants and various PS activation methods have been explored. Iohexol (IOH), as a typical iodinated X-ray contrast media, poses a threat to human health and ecological environment, which is difficult to be removed by conventional treatment methods. In our work, a photocatalytic coupling persulfate system was constructed for efficient IOH degradation. A novel binary photocatalyst of biochar loaded with perylene diimide (PDI/BC, PB) was successfully prepared via a one-pot water bath heating method, which achieved BC acidification and PDI self-assembly simultaneously. Different mass ratios of BC and PDI lead to variance in average particle size, electronegativity, bandgap width and electron/hole separation efficiency. The optimized efficiency of 10 mg/L IOH on PB-9 (PDI:BC = 1:9, w/w) reached 100% in 2 h with 1.5 mM sodium persulfate under visible light irradiation. Based on the results of trapping experiments and electron paramagnetic resonance, holes and hydroxyl radicals were the dominant active species and the free radical chain reaction and mutual conversion reaction of active species occurred. The amide hydrolysis, amine and C-OH oxidation, hydrogen extraction, deiodination and OH addition were observed during the degradation process. Density functional theory calculation was conducted to confirm the free radical attack sites. The findings of this work demonstrate that metal-free supramolecular loaded photocatalyst has the potential for application in the removal of organic pollutants for water remediation.

WITHDRAWN: g-C3N4-nanosheet/ZnCr2O4 S-scheme heterojunction photocatalyst with enhanced visible-light photocatalytic activity for degradation of phenol and tetracycline [Sep. Purif. Technol. (2021) 118511

Abstract Photocatalytic processes based on semiconductors have been regarded as an efficient environmental purification technology to remove different contaminants from wastewater, and summon for impressive photocatalysts is incessant. Herein, a new step-scheme nanocomposite constructed of g-C3N4-nanosheet/ZnCr2O4 heterojunction is synthesized for effective degradation of phenol and tetracycline. The prepared g-C3N4-nanosheet/ZnCr2O4 nanocomposite exhibits photocatalytic performance for phenol and tetracycline degradation more than 5.8 and 22.5-folds greater than bare g-C3N4-nanosheet and 6.2 and 34.2-times larger than pure ZnCr2O4, respectively. The recycling tests also display that about 88.2% and 89.7% of phenol and tetracycline can be photo-degraded by binary g-C3N4-nanosheet/ZnCr2O4 photocatalyst even after five cycles. The prepared binary photocatalyst pursues a step-scheme charge transfer mechanism that leads to the significant photocatalytic activity under visible illumination. The superior photoability is assigned to the excellent visible light-harvesting capability and fast charge separation and transportation characteristics. The present research serves as a principle route to design and extend striking step-scheme g-C3N4-based nanocomposites with promising environmental purification and solar fuel generation usage.

RETRACTED: Recent advancements of spinel ferrite based binary nanocomposite photocatalysts in wastewater treatment

A lot of studies on spinel ferrites (MFe2O4, M = divalent metal ion) and their binary nanocomposites as photocatalysts in the decontamination of wastewater have been performed, because MFe2O4 nanoparticles are relatively stable, biocompatible and low-cost efficient photocatalyst. The separation of MFe2O4 photocatalyst is easy owing to its excellent magnetic behavior. With this background, the recent developments on photocatalytic performances of MFe2O4 based binary nanocomposites were comprehensively reviewed. Especially, a focus on MFe2O4/metal oxides, MFe2O4/carbon based materials, MFe2O4/polymers, MFe2O4/metal nanoparticles and MFe2O4/other compounds for the photocatalytic degradation of dyes, emerging contaminants and inorganic pollutants has been thoroughly given. The advantages of MFe2O4 based nanocomposites as photocatalysts were also discussed. In addition, the possible pathway of active free radical generation by these photocatalysts under visible and ultraviolet irradiation has been explained. A comparison of photocatalytic activities of MFe2O4 based binary nanocomposites with recent reports has been carried out. This review concludes that MFe2O4 based binary nanocomposites have potential capacity in water purification technology. Nevertheless, their practical utilization in water treatment plants still needs to be further studied.

In-situ preparation of double Z-scheme Bi2S3/BiVO4/TiO2 ternary photocatalysts for enhanced photoelectrochemical and photocatalytic performance

In this study, novel double-Z-scheme Bi2S3/BiVO4/TiO2 (BVT) heterostructured photocatalysts were prepared using continuous hydrothermal methods. The in situ conversion of BiVO4/TiO2 (VT) binary photocatalysts into BVT ternary photocatalysts with large optical absorption coefficients was achieved. Compared to TiO2 nanorod (TNR) arrays, BVT photocatalysts extend the light absorption range to the near-infrared with consistently high absorption intensities. Photoelectrochemical tests demonstrate that BVT(4) achieves the highest transient photocurrent (110 µA/cm2) of approximately 11 times that of TiO2 (10 µA/cm2). The photocatalytic performances of all samples were investigated by degrading methyl orange (MO) under visible light irradiation. The results show that BVT(4) possesses the best degradation efficiency (76.3%) which is about 4 times higher than that of bare TNR (19.7%). The outstanding photocatalytic performance can be attributed to the double Z-scheme charge transfer path, which effectively promotes the separation and transfer of electron-hole pairs, resulting in a strong redox activity of the accumulated charge to decompose organic dyes during a degradation reaction.

Synthesis of Novel Cunb2o6/G-C3n4 Binary Photo-Catalyst Towards Efficient Visible Light Reduction of Cr (Vi) and Dyes Degradation for Environmental Remediation

Synthesis of Novel Cunb2o6/G-C3n4 Binary Photo-Catalyst Towards Efficient Visible Light Reduction of Cr (Vi) and Dyes Degradation for Environmental Remediation

In English

The use of oxygen modified graphite-like carbon nitride (C3N4Ox), photosensitive in the visible region of the optical spectrum, along with TiO2, photocatalytically active only in the ultraviolet region of the spectrum, in the C3N4Ox/TiO2 binary photocatalyst, opens a possibility of the use of sunlight energy. To increase opportunities of various kinds of photochemistry-related applications of C3N4Ox/TiO2 photocatalyst, the phase composition of the TiO2 matrix and morphology of nanoparticles of composite and their optical properties are very important. A novel composite material, C3N4Ox/TiO2, was synthesized in the present work in accordance with the approach developed in Frantsevich Institute for Problems of Materials Science of NASU for the synthesis of powdered oxygen-doped carbon nitride (C3N4Ox) by CVD method under the special reactionary conditions of the melamine pyrolysis, in particular, in the presence of a fixed air volume. Deposition of C3N4Ox carried out on the surface of a nanostructured powdered TiO2 matrix of different phase composition, rutile or anatase. The deposition of C3N4Ox (~5 % O) on both rutile and anatase nanopowders was confirmed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis-DRS) methods. SEM micrographs (recorded with a MIRA3 TESCAN scanning electron microscope) of nanoparticles of both C3N4Ox/TiO2 composites (anatase and rutile phases) demonstrate the arrangement of TiO2 as separate globular nanoparticles and clusters between the plates and in the channels of the porous scaly plates C3N4Ox. However, the anatase phase nanoparticles (synthesized in IPM NASU) have a higher dispersion, the average size of non-aggregated almost monodisperse particles is about 10 nm. Using UV/Vis spectroscopy, it has been found that a redshift of long-wavelength edge of the fundamental absorption band of the spectra is observed when going from TiO2 (anatase), TiO2 (rutile), C3N4, C3N4Ox/TiO2 (anatase), C3N4Ox/TiO2 (rutile) and, then, to C3N4Ox, and the band gap decreases from 3.2, 3.0, 2.6, 2.4, 2.25 to 2.1 eV in the above sequence of materials. In such a case, C3N4Ox/TiO2 (especially deposited on anatase phase) would absorb more visible light than g-C3N4 and TiO2, by generating more charges which favor the improvement in the photoactivity of the catalysts.

Facile solvothermal synthesis of a Z-Scheme 0D/3D CeO2/ZnIn2S4 heterojunction with enhanced photocatalytic performance under visible light irradiation

Reasonable designing heterojunction photocatalysts is an effective way to improve the photocatalytic activity of semiconductor. Herein, the efficient binary heterojunction photocatalyst formed between zero-dimensional (0D) CeO2 nanoparticles and three-dimensional (3D) floriated shaped ZnIn2S4 microspheres was synthesized by a simple solvothermal method. A series of analytical methods were used to characterize the optical properties and morphology of CeO2/ZnIn2S4 composite photocatalysts. Photodegradation experimental results showed that CeO2/ZnIn2S4 composites displayed strong photocatalytic activity for the degradation of tetracycline (TC) with heavy concentrations (30 mg/L). The as-obtained optimum 10 wt% CeO2/ZnIn2S4 sample displays high degradation efficiency of 91% within 120 min, which is about 12.9 and 3.03 times higher than that of pure CeO2 and ZnIn2S4, respectively. The enhanced photocatalytic activity is ascribed to the formation of Z-scheme heterojunction between CeO2 and ZnIn2S4, which contributes to the increased surface area, enhanced redox ability and high separation efficiency of photogenerated charge carriers. The degradation pathways and intermediate products of TC over CeO2/ZnIn2S4 composite were analyzed by liquid chromatography-mass spectrometry (LC/MS) measurement. This study provides a new approach to prepare of efficient 0D/3D-based Z-scheme heterojunction photocatalysts.

Noble-metal-free ultrathin MXene coupled with In2S3 nanoflakes for ultrafast photocatalytic reduction of hexavalent chromium

The conversion of highly toxic heavy metal hexavalent chromium (Cr(VI)) in the natural environment into low-toxic trivalent chromium (Cr(III)) is one of the research topics of great concern. Herein, a binary noble-metal-free photocatalyst consisting of ultrathin MXene (Ti3C2) and indium sulfide (In2S3) is prepared for ultrafast photocatalytic reduction of Cr(VI) to Cr(III) under visible light. A simple electrostatic assembly and reflow method uniformly coats the In2S3 nanoflakes on the surface of hollow Ti3C2 nanospheres, which effectively boost the separation of charges and thus enhance the photocatalytic performance. Thus, the prepared heterojunction can reduce Cr(VI) to Cr(III) completely within 6 min with an ultrafast rate constant of k = 0.739 min−1. More importantly, the appropriate band structure ensures the stable existence of Cr(III). Therefore, it provides a new insight for economic MXene-based binary photocatalysts for efficient environmental remediation.

Highly Active Binary Exfoliated MoS2 Sheet–Cu2O Nanocrystal Hybrids for Efficient Photocatalytic Pollutant Degradation

Semiconductor–semiconductor binary photocatalysts with complementary band gaps and desirable conduction band (CB)/valence band (VB) potentials are considered as attractive photocatalysts. In this study, binary exfoliated MoS2 sheet–Cu2O nanocrystal (e‐MoS2sheet–Cu2ONC) hybrids have been synthesized through direct growth of Cu2O nanocrystals on e‐MoS2 sheets. Under visible light irradiation, electrons and holes are efficiently generated in the binary e‐MoS2sheet–Cu2ONC hybrids. In addition, migration of electrons and holes is also accelerated into opposite e‐MoS2 sheets and Cu2O nanocrystals, respectively. The efficient charge carrier formation and transfer in the e‐MoS2sheet–Cu2ONC hybrids are attributed to their morphological and compositional features, which boost their photocatalytic performance toward methyl orange degradation.