Ternary Heterojunction Research Articles

Construction of Z-scheme heterojunction C3N4/N-CQDs@W18O49 for full-spectrum photocatalytic organic pollutant degradation

To achieve efficient solar-energy conversion, the development of full-spectrum light-driven photocatalysts with valid charge separation performance from UV to NIR wavelengths is a key challenge. Herein, a full-spectrum light-driven g-C3N4/nitrogen doped carbon quantum dots/W18O49 (C3N4/N-CQDs@W18O49) ternary heterojunction catalyst was fabricated via a solvothermal and hydrothermal method. The prepared ternary heterojunction was shown to exhibit high photocatalytic activity under full-spectrum light, particularly in the NIR region, for degrading the organic pollutants methyl blue (MB), methyl orange (MO), ciprofloxacin (CIP) and tetracycline (TC). XRD, XPS and TEM analysis demonstrated that the synergistic effects of Z-scheme dual-channel charge transfer pathways and localized surface plasmon resonance (LSPR) effects contributed to the high photocatalytic activity. Under UV–vis light irradiation, the Z-scheme pathway enhanced photogenerated charge separation, maintaining the redox of photogenerated electrons and holes for the catalytic reaction. The LSPR effect of the nonmetallic plasma W18O49 broadened the catalytic response to the NIR region, thus improving light utilization. The introduced N-CQDs provided an excellent photoelectron transport medium for electron-hole transfer and separation. This study established an efficient strategy for the preparation of full-spectrum-driven photocatalysts for organic pollutant degradation.

Synergistic charge transfer on n-WO3/p-WS2/Au ternary heterojunction material for solar energy-driven sustainable H2 production

This study investigated the effects of changes in charge transport and photo-quantity on photocatalytic water splitting by a new ternary heterojunction with the structure n-WO3/p-WS2/Au, in which gold (Au), an electron transport medium, was inserted between negative (n)-type tungsten oxide (WO3) plates and a positive (p)-type tungsten sulfide (WS2) sheet. When two particles (n-WO3 and p-WS2) were used individually as catalysts, no water splitting occurred, even after a sufficient lapse of time. However, the decomposition of methyl orange on the n-WO3 single particle and the reduction of Ag+ ions on the p-WS2 single particle occurred favorably. In contrast to the single particle results, with the n-WO3/p-WS2 heterojunction particle, hydrogen was generated at 10.30 μmol g–1 h–1 by water splitting, and with the n-WO3/p-WS2/Au ternary heterojunction particle, more than double this amount of hydrogen was generated. A lower photoluminescence intensity, higher photocurrent density, longer electron/hole recombination time, and faster electron transport rates were possible with the ternary heterojunction particle. The interparticle junction resulted in synergy in the photochemical properties, with the formation of effective redox reaction sites. In particular, the loaded Au acted as an electron trapper that attracted electrons, rather than the surface plasmon resonance effect, thereby expanding the sites for reduction reactions in the particle and improving hydrogen generation. Eventually, it was found that the charge transfer on the n-WO3/p-WS2/Au ternary heterojunction particles progressed by an M-scheme.

In Situ Growth Intercalation Structure MXene@Anatase/Rutile TiO2 Ternary Heterojunction with Excellent Phosphoprotein Detection in Sweat.

Abnormal protein phosphorylation may relate to diseases such as Alzheimer’s, schizophrenia, and Parkinson’s. Therefore, the real-time detection of phosphoproteins in sweat was of great significance for the early knowledge, detection, and treatment of neurological diseases. In this work, anatase/rutile TiO2 was in situ grown on the MXene surface to constructing the intercalation structure MXene@anatase/rutile TiO2 ternary heterostructure as a sensing platform for detecting phosphoprotein in sweat. Here, the intercalation structure of MXene acted as electron and diffusion channels for phosphoproteins. The in situ grown anatase/rutile TiO2 with n-n-type heterostructure provided specific adsorption sites for the phosphoproteins. The determination of phosphoprotein covered concentrations in sweat, with linear range from 0.01 to 1 mg/mL, along with a low LOD of 1.52 μM. It is worth noting that, since the macromolecular phosphoprotein was adsorbed on the surface of the material, the electrochemical signal gradually decreased with the increase of phosphoprotein concentration. In addition, the active sites in the MXene@anatase/rutile TiO2 ternary heterojunction and synergistic effect of the heterojunction were verified by first-principle calculations to further realize the response to phosphoproteins. Additionally, the effective diffusion capacity and mobility of phosphoprotein molecules in the ternary heterojunction structure were studied by molecular dynamics simulation. Furthermore, the constructed sensing platform showed high selectivity, repeatability, reproducibility, and stability, and this newly developed sensor can detect for phosphoprotein in actual sweat samples. This satisfactory sensing strategy could be promoted to realize the noninvasive and continuous detection of sweat.

Nanoflower-like CdS and SnS2 loaded TiO2 nanotube arrays for photocatalytic wastewater treatment and hydrogen production

In this work, nanoflower-like CdS/SnS2/TiO2 NTs ternary heterojunction photocatalysts were synthesized by a hydrothermal method, the relationship between the morphology, microscopic morphology, crystallinity, elemental presence state and hydrogen production performance of the ternary photocatalysts were investigated by SEM, TEM, XRD and XPS, respectively. The photocatalytic performance, electrochemical property and hydrogen production capacity of CdS/SnS2/TiO2 NTs were compared with pure TiO2 NTs, CdS/TiO2 NTs and SnS2/TiO2 NTs. After 2 h of photocatalytic reaction, the removal efficiency of MB wastewater reached 100%, and the photocatalytic efficiencies toward RhB and Cr(VI) removal reached 86.08% and 80.93% after 3 h, respectively. The electron spin resonance (ESR) technique certified the active radical groups that played a role in the catalytic process and further investigated the possible photocatalytic mechanism. Hydrogen production per unit time achieved 97.14 μmol h−1 cm−2, this work provides the new technique to achieve solar energy conversion for hydrogen generation.

Efficient photocatalytic hydrogen evolution on amorphous MoSx-modified CdS/KTaO3 heterojunctions under visible light irradiation

Constructing heterostructures with efficient charge separation is a promising route to improve photocatalytic hydrogen production. In this paper, MoSx/CdS/KTaO3 ternary heterojunction photocatalysts were successfully prepared by a two-step method (hydrothermal method and photo deposition method), which improved the photocatalytic hydrogen evolution activity. The results show that the rate of hydrogen evolution for the optimized photocatalyst is 2.697 mmol g−1·h−1under visible light, which is 17 times and 2.6 times of the original CdS (0.159 mmol g−1 h−1) and the optimal CdS/KTaO3(1.033 mmol g−1 h−1), respectively, and the ternary photocatalyst also shows good stability. The improvement on photocatalytic hydrogen evolution performance can be attributed to the formation of heterojunction between the prepared composite materials, which effectively promotes the separation and migration of photo-generated carriers. Amorphous MoSx acts as an electron trap to capture photogenerated electrons, providing active sites for proton reduction. This provides beneficial enlightenment for hydrogen production by efficiently utilizing sunlight to decompose water.

Effect of different carbon dots positions on the transfer of photo-induced charges in type I heterojunction for significantly enhanced photocatalytic activity

The design of highly efficient photocatalysts is a hot topic in the field of photocatalysis. Herein, two kinds of ternary heterojunctions with coating carbon dots (CDs) on the different positions of ZnFe2O4@ZnIn2S4 heterojunctions (CDs-ZnFe2O4@ZnIn2S4 and ZnFe2O4@ZnIn2S4-CDs) were developed for exploring the role of CDs on charge transfer of heterojunctions. Compared with ZnFe2O4@ZnIn2S4-CDs (CDs are fixed to the exterior of the core–shell structure), CDs-ZnFe2O4@ZnIn2S4 (CDs are fixed to the interior of the core–shell structure) exhibits a more efficient acceleration of migration and separation of photo-induced charges. As expected, the optimal CDs-ZnFe2O4@ZnIn2S4 sample exhibits the optimized tetracycline (TC, 30 mg/L) degradation rate of 87.3 % in 120 min under visible light irradiation. This work reveals that CDs existing at the contact interface of heterojunction establish smooth and fast channels for electron transport, accelerate electron transport and prevent the recombination of electron-hole pairs, thus significantly improving the photocatalytic performance of type-I heterojunction constructed by ZnFe2O4 and ZnIn2S4.

A double Z‐scheme catalyst BiOI/g‐C3N4/Bi2WO6 for enhanced photocatalytic activity

AbstractBACKGROUNDTo enhance photocatalyst activity, a Z‐scheme ternary heterojunction of g‐C3N4 and BiOI co‐modified with Bi2WO6 (BiOI/g‐C3N4/Bi2WO6 (BCB)) was prepared. The double Z‐scheme catalyst is advantageous but not well studied for compositing low‐cost g‐C3N4 with Bi‐containing components such as BiOI and Bi2WO6.RESULTSFor g‐C3N4 and BiOI, we determined the optimal doping ratios of 3 wt% BiOI/10 wt% g‐C3N4 /Bi2WO6. It catalyzed almost complete degradation of (100 mg L−1) rhodamine B (RhB) under visible light irradiation (95% in 20 min and 100% in 30 min), with a significant reaction kinetic constant of 0.245 min−1. The remaining high total organic carbon removal rate of RhB, even after five cycles of the experiment, and the good removal effect for different concentrations of tetracycline (TC) proved the effectiveness of the catalyst.CONCLUSIONThe e−, h+, and ·OH, ·O2− reactive species work together, leading to rapid pollutant degradation. The developed triple‐component double Z‐scheme heterojunction catalyst has promising applications in pollution control. © 2022 Society of Chemical Industry (SCI).

Construction of CeO2/YMnO3 and CeO2/MgAl2O4/YMnO3 photocatalysts and adsorption of dyes and photocatalytic oxidation of antibiotics: Performance prediction, degradation pathway and mechanism insight

A simple two step method was developed for fabrication of ternary heterojunctions of YMnO3/CeO2/MgAl2O4 (YCM) composite photocatalysts, which shows well adsorption capacity for the adsorption of Congo red and photocatalytic activity for the degradation of tetracycline hydrochloride (TC-HCl) under visible light irradiation. Systematic studies suggested that the YCM composite photocatalysts exhibit high optical absorption coefficient, charge carrier transfer and separation efficiency, adsorbed oxygen concentration and interface defect, high adsorption capacity and photocatalytic activity. The back propagation (BP) neural network model, whale optimization algorithm (WOA) and genetic algorithm (GA) were used to predict the adsorption capacity of YC composite photocatalysts, and GA model demonstrated the best predictive ability. The high adsorption can be assigned to the synergistic effect of electrostatic interaction, ion exchange and hydrogen bonding. Capture experiments revealed that photogenerated holes, hydroxyl and superoxide radicals are the main active species during the photocatalytic process for the YCM composite photocatalysts. Possible degradation pathways of TC-HCl over YCM composite photocatalysts under visible light irradiation were proposed through the identification of intermediates using high-performance liquid chromatography-tandem mass spectrometry (HPLC–MS). This work demonstrated a huge potential of YCM composite photocatalysts as an eco-friendly photocatalyst for adsorption of dye and degradation of drug.

RETRACTED: Ionic liquid-assisted preparation of g-C3N4/RGO co-intercalated CuBi2O4 hierarchical nanoflower and enhancement of the photocatalytic activity

A new p-n type CBO/CN/RGO ternary heterojunction photocatalyst combining three-dimensional multi-stage rosette CuBi2O4 and two-dimensional g-C3N4 and RGO flakes was successfully prepared by ionic liquid-assisted hydrothermal method. The successful construction of p-n heterojunctions of CBO/CN/RGO composites was verified by means of UV–vis diffuse reflection, Mott Schottky curves and TEM, and construction the heterojunctions significantly improved that of the transfer and transport speed of photogenerated carriers. The photocatalytic degradation of MO by CBO/CN/RGO-6% reached 91.83% within 150 min, while the kinetic constants of degradation k were 9.7 and 7.9 times greater than those of single-phase CBO and g-C3N4, respectively. Three cycles of experiments demonstrated that the degradation efficiency of CBO/CN/RGO-6% composites remained above 88% for RhB, which fully proved that the CBO/CN/RGO-6% composites possessed good chemical stability. Based on its excellent photocatalytic performance and good stability, CBO/CN/RGO-6% is expected to be the preferred material for environmental wastewater treatment.

Magnetic recyclable g-C3N4/Fe3O4@MIL-100(Fe) ternary catalyst for photo-Fenton degradation of ciprofloxacin

The slow Fe(III)/Fe(II) cycle rate seriously limits the photo-Fenton degradation efficiency. In this work, a novel g-C3N4/Fe3O4@MIL-100(Fe) ternary heterojunction catalyst was prepared via a facile in-situ route under a mild reaction condition, and was further used as a photo-Fenton catalyst for efficient degradation of ciprofloxacin via the synergistic effect. Compared with g-C3N4 and Fe3O4@MIL-100(Fe), the composite g-C3N4/Fe3O4@MIL-100(Fe) exhibited excellent photo-Fenton catalytic activity for high concentration ciprofloxacin (up to 200 mg L−1); approximately 94.7% of CIP was degraded within 120 min light irradiation. It is concluded that g-C3N4 can produce photo-generated electron transfer and further accelerate Fe(III)/Fe(II) cycle, leading to an improvement in the degradation efficiency of ciprofloxacin. In addition, the catalyst presents excellent reusability, whereas the removal efficiency of CIP attained 70.0% after three cycles. This study provided a means to enhance the photo-Fenton activity of Fe-MOFs-based catalysts.

FeOOH interlayer with storing holes applied to construct WO3/FeOOH/Cu2O ternary heterojunction photoanode with dual built-in electric filed for efficient PEC cell

Broader visible light response, higher carrier separation efficiency and injection efficiency are extremely important methods to enhance photoelectrochemical (PEC) performances of WO 3 . In this work, FeOOH with the property of storing holes is firstly applied to modify WO 3 /Cu 2 O heterojunction as an interlayer, and the WO 3 /FeOOH/Cu 2 O ternary heterojunction with excellent PEC performances is obtained. The separation efficiencies of photoinduced carrier in bulk is enhanced to 29.33% with the formation of dual built-in electric filed as well as the storage of photoinduced carriers transferred from WO 3 in FeOOH, which is 3.27 folds higher than that of bare WO 3 . With the synergistic effect of expanded light absorption and accelerated charges transfer, the photocurrent density of 2.14 mA/cm 2 at 1.23 V vs. RHE is achieved by WO 3 /FeOOH/Cu 2 O ternary heterojunction. This work can be applied for reference to improve the PEC performance of other photoelectrodes through adequate utilization of storing holes interlayer. • WO 3 /FeOOH/Cu 2 O ternary heterojunction is prepared with FeOOH as interlayer for PEC water splitting. • Photocurrent density of WO 3 /FeOOH/Cu 2 O is 2.14 mA/cm 2 , which is 10.19 folds higher than that of WO 3 . • Cu 2 O particles outer layer as the primary light absorber improves the light utilization efficiency. • Ternary heterojunction with formation of dual built-in electric filed facilitates charge separation and transfer. • The effect of extracting and storing holes for FeOOH further enhance carrier separation of the heterojunction.

Integrated p-n Junctions for Efficient Solar Water Splitting upon TiO2/CdS/BiSbS3 Ternary Hybrids for Improved Hydrogen Evolution and Mechanistic Insights

The development of efficient and novel p-n heterojunctions for photoelectrochemical (PEC) water splitting is still a challenging problem. We have demonstrated the complementary nature of (p-type) BiSbS3 as a sensitizer when coupled with (n-type) TiO2/CdS to improve the photocatalytic activity and solar to hydrogen conversion efficiency. The as-prepared p-n heterojunction TiO2/CdS/BiSbS3 exhibits good visible light harvesting capacity and high charge separation over the binary heterojunction, which are confirmed by photoluminescence (PL) and electrical impedance spectroscopy (EIS). The ternary heterojunction produces higher H2 than the binary systems TiO2/CdS and TiO2/BiSbS3. This ternary heterojunction system displayed the highest photocurrent density of 5 mA·cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) in neutral conditions, and STH of 3.8% at 0.52 V vs. RHE is observed. The improved photocatalytic response was due to the favorable energy band positions of CdS and BiSbS3. This study highlights the p-n junction made up of TiO2/CdS/BiSbS3, which promises efficient charge formation, separation, and suppression of charge recombination for improved PEC water splitting efficiency. Further, no appreciable loss of activity was observed for the photoanode over 2500 s. Band alignment and interfaces mechanisms have been studied as well.

Deep-Eutectic-Solvent-Assisted Synthesis of a Z-Scheme BiVO4/BiOCl/S,N-GQDS Heterojunction with Enhanced Photocatalytic Degradation Activity under Visible-Light Irradiation.

Z-scheme heterojunction photocatalytic nanomaterial designs have attracted attention due to their high catalytic performance. Deep eutectic solvents (DESs) have been used as green, sustainable media, acting as solvents and structure inducers in the synthesis of nanomaterials. In this work, a novel visible-light-absorption-enhanced bismuth vanadate/bismuth oxychloride/sulfur, nitrogen co-doped graphene quantum dot (BiVO4/BiOCl/S,N-GQDS) heterojunction photocatalyst was prepared in a deep eutectic solvent. The photosynthetic activity of the BiVO4/BiOCl/S,N-GQDS composite was determined by the photocatalytic degradation of rhodamine B (RhB) under visible-light irradiation. The results showed that the highest photocatalytic activity of BiVO4/BiOCl/S,N-GQDS was achieved when the doping amount of S,N-GQDS was 3%, and the degradation rate of RhB reached 70% within 5 h. The kinetic and photocatalytic cycles showed that the degradation of Rhb was in accordance with the quasi-primary degradation kinetic model, and the photocatalytic performance remained stable after four photocatalytic cycles. Ultraviolet–visible diffuse reflectance (UV-DRS) and photoluminescence (PL) experiments confirmed that BiVO4/BiOCl/S,N-GQDS ternary heterojunctions have a narrow band gap energy (2.35 eV), which can effectively improve the separation efficiency of the photogenerated electron–hole pairs and suppress their complexation. This is due to the construction of a Z-scheme charge process between the BiVO4/BiOCl binary heterojunction and S,N-GQDS, which achieves effective carrier separation and thus a strong photocatalytic capability. This work not only provides new insights into the design of catalysts using a green solvent approach but also provides a reference for the study of heterojunction photocatalytic materials based on bismuth vanadate, as well as new ideas for other photocatalytic materials.

Facile synthesis of VS2/CdS/NaYF4: Yb, Er ternary heterojunctions for the visible-near-infrared-light driven photocatalysis

Developing an efficient chalcogenide photocatalyst with a broad spectral response, rapid energy and charge transfer by integrating upconversion materials and visible-light-driven photocatalyst are significant to alleviate the pressure of environmental treatment. Herein, the heterojunctions of CdS with VS2 as co-catalyst (electron transport medium) and NaYF4: Yb, Er (NYYE) upconversion material were constructed by hydrothermal method and the nanostructures were investigated, in which CdS nanoparticles are composed of cubic and hexagonal CdS with high crystallinity. Interestingly, the as-prepared VS2/CdS/NYYE heterojunctions exhibited splendid photocatalytic performance on the degradation Rh B dye for the efficiency of 97.31% under visible-near infrared light irradiation for 150 ​min. It could give the credit to the synergic effect of the enhanced interface energy transfer of upconversion material and the co-catalysis of VS2 among VS2, NYYE and CdS, where the heterojunctions could induce the efficient separation of photogenerated carriers and the emergence of high oxidative species (·O2− and h+). The alternative mechanisms of carriers and energy transfer were also discussed.

Ag nanoparticles decorated 2D/2D TiO2/g-C3N4 heterojunction for efficient removal of tetracycline hydrochloride: Synthesis, degradation pathways, and mechanism

In this study, a surfactant-assisted self-assembly method was used to synthesize atomically thin TiO2 nanosheets and construct 2D/2D TiO2/g-C3N4 heterojunctions with strong interfacial coupling. The prepared binary composites were subsequently modified using Ag nanoparticles to obtain a unique 0D/2D/2D Ag/TiO2/g-C3N4 heterojunction. Ascribed to its unique structure, the ternary heterojunction exhibited outstanding photocatalytic performance and 85.1 % tetracycline hydrochloride (TC) was decomposed within 25 min. The degradation rate of as-prepared ternary heterojunction was much higher than TiO2, g-C3N4, and TiO2/g-C3N4. The photocatalytic performance under different operating conditions (anion, initial concentration) was also investigated. The outstanding photocatalytic performance of Ag/TiO2/g-C3N4 can be ascribed to its efficient solar-light utilization capacity and low photogenerated charge carrier recombination. Moreover, possible TC degradation pathways were proposed and toxicity prediction indicated that most TC intermediates were decreased during the photocatalytic process. Besides, the possible photocatalytic mechanism was proposed based on experimental data and work function calculations.

Active sites modification and superior carriers separation synergistically boosted hydrogen production of Bi/Bi2MoO6/ZnIn2S4 non-noble metal S-scheme photocatalyst

Novel Bi/Bi2MoO6/ZnIn2S4 is not only cost-effective compared to noble metals, but also shows superior hydrogen production. Comprehensive characterization illustrated that the S-scheme heterojunction and excellent photon utilization capability of the photocatalyst were the main factors that enhanced its hydrogen production performance. The X-ray photoelectron spectroscopy illustrated the elemental composition of the catalyst and the presence of Bi metal in ternary heterojunction. The photoluminescence and electrochemical characterization proved that S-scheme heterojunction Bi/Bi2MoO6/ZnIn2S4 promoted the separation of photogenerated carriers. The amount of hydrogen produced by Bi/Bi2MoO6/ZnIn2S4 was 2306.90 µmol g−1 under visible light illumination for 5 h. It was 4.3, 29.6 and 2.2 times more than those of ZnIn2S4, Bi2MoO6/ZnIn2S4 and Pt/ZnIn2S4, respectively. The excellent hydrogen production activity of the ternary complexes may be attributed to the following: (1) Bi/Bi2MoO6 could replace precious metals to enhance reactive sites of ZnIn2S4. (2) Metal Bi could produce surface plasmon resonance effect facilitating light absorption, and Bi acted as an electron bridge promoting charge transfer. (3) The charge transfer mechanism of S-scheme heterojunction and hot electrons injection process of Bi metal synergistically drove the photocatalytic hydrogen production. This work provides an innovative method for the construction of visible-light-driven photocatalysts without using precious metals.

Preparation and Photocatalytic Performance of MoS2/ZnS/ZnO‐T Heterojunction Photocatalyst for Dye Degradation in Water

AbstractIn this study, a ternary heterojunction which consists of molybdenum disulfide (MoS2), zinc sulfide (ZnS), and tetrapod‐like zinc oxide (ZnO‐T) nanostructures is prepared through a facile hydrothermal method. Benefiting from the generation of 1T phase MoS2 and ZnS with high photoelectrochemical properties, the material exhibits outstanding charge separation and transfer performances while degrading methylene blue. According to the results of the photodegradation experiment, the MoS2/ZnS/ZnO‐T composite displays not only excellent photocatalytic reduction activity but also remarkable adsorption performance. The photocatalytic activity is improved twice higher, and the first‐order rate constant is 4.22 times than pure ZnO‐T. Moreover, the good recyclability after 3 continuous cycles implies excellent stability for practical applications. This study develops a high‐efficient photocatalyst for contaminated water treatment.

Silver and zinc oxide decorated on reduced graphene oxide: Simple synthesis of a ternary heterojunction nanocomposite as an effective visible-active photocatalyst

Ternary nanocomposites of Ag-ZnO-rGO were prepared through an in-situ hydrothermal process in presence of 1, 8-diamino-3, 6-dioxaoctan (DDO). It was tried to result homogeneous fine particles by changing the effective parameters. Then, photocatalytic performance of the optimized sample was investigated by removing Rhodamine B (RhB) dye as an organic pollutant. Next, the photocatalytic efficiency was optimized by two operational parameters: concentration of dye and pH of solution. On the other sides, the results showed that the silver content amount in the composite can affect the photocatalytic yield. Therefore, ideal efficiency (98.92%) was obtained when the concentration of RhB solution was 10 ppm and pH was adjusted to 11, in the presence of Ag-ZnO-rGO nanocomposite with a silver content of about 5%. According to the findings, DDO can be considered an important agent for the synthesis of Ag-ZnO-rGO nanocomposite which should be used as a photocatalyst.

A novel double S-scheme photocatalyst Bi7O9I3/Cd0.5Zn0.5S QDs/WO3−x with efficient full-spectrum-induced phenol photodegradation

In this work, Bi7O9I3/Cd0.5Zn0.5S QDs/WO3−x ternary heterojunction with full spectrum response was prepared and applied in the photodegradation of phenol. The results of photocatalytic experiments showed that the prepared Bi7O9I3/Cd0.5Zn0.5S QDs/WO3−x heterojunction had the highest performance under full spectrum, visible and near-infrared light irradiation, and the reaction rates were 4.02, 3.75 and 5.71 times that of pure Bi7O9I3, respectively. This performance improvement results from the construction of double S-scheme heterojunction and the full-spectrum response, which had effective charge distribution and migration as well as an excellent response to sunlight. In addition,·OH and·O2- took the lead role in the process of photodegradation. Combined with the free radical-trapping experiment, ESR experiment and DFT theoretical calculation, the photocatalytic mechanism of double S-scheme system was proposed. This work is contributory to designing novel photocatalytic materials with dual S-scheme heterojunction and the efficient purification of wastewater in environmental remediation.

Solar-light-driven ternary MgO/TiO2/g-C3N4 heterojunction photocatalyst with surface defects for dinitrobenzene pollutant reduction

Defect engineering and heterojunction are promising strategies to improve the photocatalytic performance of particular catalyst through effective charge carrier separation and transport. Herein, we developed Z-scheme MgO/TiO2/g-C3N4 ternary heterojunction photocatalyst with surface defects and effective charge separation for reduction of recalcitrant dinitrobenzene isomers under simulated solar light irradiation. Mott-Schottky (MS) plot analysis and electron spin resonance (ESR) radical trapping experiment suggested the formation of Z-scheme heterojunction at the interface of TiO2/g-C3N4, which played a crucial role in the electron-hole separation. Incorporating MgO into the structure further enhances charge separation via Ti3+ and oxygen vacancy (OV) defects formation at the TiO2/MgO interface as confirmed by electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) analyses. Besides, the surface basicity of MgO enhanced conversion of dinitrobenzene (DNB) isomers through formation of nitrophenylhydroxylamine intermediate which can easily be reduced to phenylenediamines (PDAs). As confirmed by high performance liquid chromatography (HPLC) analysis, excellent selectivity for PDAs (95–98%) was achieved in 90 min with ternary MgO/TiO2/g-C3N4 composite compared to the binary MgO/TiO2 and TiO2/g-C3N4. A possible reaction pathway and photocatalytic reduction mechanism were proposed and elucidated. This work demonstrated an effective strategy to reduce recalcitrant dinitrobenzene isomers using efficient, low-cost, and environmental benign photocatalyst with a facile identification of reaction intermediates.