Efficient Electron-hole Separation Research Articles

Synergistic effects of CQDs and oxygen vacancies on CeO2 photocatalyst for efficient photocatalytic nitrogen fixation

The combination of carbon quantum dots (CQDs) with oxygen vacancies (OVs) provides a promising approach to achieving efficient photocatalytic nitrogen fixation. It was by a hydrothermal method that CQDs-modified CeO2 composites (CQDs/CeO2) were synthesized. The synergistic effects of CQDs and OVs on CeO2 photocatalyst enhanced interfacial electron transfer capabilities, thus the photocatalytic nitrogen fixation was significantly enhanced. CQDs/CeO2 exhibited the most superior efficiency in photocatalytic nitrogen fixation, reaching 826 μmol·g−1·h−1, when the addition of CQDs was 200 µL. It was the introduction of CQDs that effectively regulated the concentration of OVs. OVs captured the electrons, thus promoting electron transfer. This enhancement not only improved the electron-hole separation efficiency in CQDs/CeO2 but also greatly promoted the adsorption and activation of N2 by OVs. This work offered a novel strategy for designing efficient photocatalysts for nitrogen fixation.

(Co, S)-Codoped BiOBr as a novel signal probe coupled with LAMP (H+)-pH responsive photoelectrochemistry biosensor for ultrasensitive detection of microRNA

Herein, Co/S-BiOBr as a novel photoelectric material with excellent photoelectric property was prepared by cation–anion co-doping method with LAMP (H+)-pH responsive as signal amplification to construct a photochemical (PEC) biosensor for ultrasensitive detection of microRNA-221 (miRNA-221) related to triple-negative breast cancer (TNBC). Notably, not only the lattice distortion caused by S doping could elevate the photo-generated electron-hole separation efficiency, but also the tune of electronic structure by Co doping promoted electron transfer and decreased recombination rate, thus significantly improving the photoelectric performance. Furthermore, in the aid of Loop-mediated isothermal amplification (LAMP), a few miRNA-221 could be converted to abundant LAMP(H+) for changing the configuration of the Fc-DNA probe, which made the ferrocene (Fc) approach to electrode via pH-responsive for hindering the transmission of electrons, resulting in a significantly reduced photocurrent signal to enhance the sensitivity of the biosensor. The proposed PEC biosensor performed a wide range from 1 fM to 10 nM with a detection limit of 0.24 fM. This work prepared a novel material with efficient photoelectric efficiency for sensitive detection of biomolecules and exhibited enormous potential in disease diagnosis.

Self-Assembly Regulated Photocatalysis of Porphyrin-TiO2 Nanocomposites.

Photoactive artificial nanocatalysts that mimic natural photoenergy systems can yield clean and renewable energy. However, their poor photoabsorption capability and disfavored photogenic electron-hole recombination hinder their production. Herein, we designed two nanocatalysts with various microstructures by combining the tailored self-assembly of the meso-tetra(p-hydroxyphenyl) porphine photosensitizer with the growth of titanium dioxide (TiO2). The porphyrin photoabsorption antenna efficiently extended the absorption range of TiO2 in the visible region, while anatase TiO2 promoted the efficient electron-hole separation of porphyrin. The photo-induced electrons were transferred to the surface of the Pt co-catalyst for the generation of hydrogen via water splitting, and the hole was utilized for the decomposition of methyl orange dye. The hybrid structure showed greatly increased photocatalytic performance compared to the core@shell structure due to massive active sites and increased photo-generated electron output. This controlled assembly regulation provides a new approach for the fabrication of advanced, structure-dependent photocatalysts.

Cu-Fe bimetallic MOFs with long lifetime separated-state charge for enhancing selectivity for CO2 photoreduction to CH4

Improving the CO2 to CH4 conversion efficiency of Cu metal-organic frameworks (Cu-MOFs) catalysts is important for promoting carbon capture and utilization. In this work, a series of novel Cu-Fe bimetallic MOFs photocatalysts (Cu-BTB-Fe with 0.5 wt%, 1.0 wt%, 2.0 wt%, and 4.0 wt% of Fe; H3BTB = 1,3,5-tris(4-carboxyphenyl) benzene) were synthesized by a bimetallic site (Cu and Fe) design strategy in order to improve the electron-hole separation efficiency and CO2 adsorption activation. Findings indicated that the as-synthesized Cu-BTB-2 wt% Fe catalyst exhibited excellent catalytic performance for the conversion of CO2 to CH4 and CO under simulated sunlight irradiation, providing a yield of 32.20 μmol∙g−1∙h−1 and a selectivity of 69.24 % for CO2 to CH4 conversion as well as a yield of 14.29 μmol∙g−1∙h−1 for CO2 to CO conversion without liquid phase products. This is because the Cu-Fe bimetallic sites can continuously supply photoinduced electrons with long separated-state decay lifetime to efficiently activate CO2. Specifically, the Cu-BTB-Fe catalysts provided a high proportion of effective photoinduced electrons with long decay lifetime for the CO* hydrogenation process through a unique electron transfer mechanism, while the strong affinity between CO2 and [Cu2(COO)4]-Fe active units enabled high CO2 adsorption activation and rapid CO2 reduction. The present approach, hopefully, would help to establish feasible pathway for the development of novel highly selective Cu-based MOFs photocatalysts for CO2 photocatalytic reduction yielding CH4.

ZnIn2S4 nanostructure grown on electronegative h-BN for highly efficient photocatalytic hydrogen evolution

The photo-corrosion issue inherent in metal sulfide semiconductors is quite pronounced, making the enhancement of electron-hole pair separation efficiency in these photocatalysts a pivotal strategy for boosting photocatalytic hydrogen production. This study introduces a novel approach where hexagonal boron nitride (h-BN) acts as a substrate for the in situ growth of ZnIn2S4 nanostructures, resulting in the formation of h-BN@ZnIn2S4 (BN@ZIS) nanocomposites. The electronegativity of h-BN nanosheets is harnessed to facilitate the recombination or electrostatic attraction of photogenerated holes in the ZnIn2S4 photocatalyst. This strategy effectively promotes the separation of photogenerated electron-hole pairs, which is crucial for enhancing photocatalytic performance. The microstructure, morphology and optical properties of BN@ZIS nanocomposites were meticulously investigated. The findings reveal that the incorporation of h-BN nanosheets loads to a more uniform dispersion of the ZnIn2S4 nanostructure, which not only increases the specific surface area but also fosters a tight heterojunction interface between h-BN and ZnIn2S4. In conclusion, the photocatalytic hydrogen production capabilities of the BN@ZIS nanocomposites were rigorously evaluated. Pure h-BN lacks photocatalytic hydrogen production activity. Conversely, the optimized BN@ZIS composite demonstrated a remarkable enhancement, exhibiting a photocatalytic efficiency that is 9.65 times greater than that of pristine ZnIn2S4. Furthermore, a plausible mechanism by which BN@ZIS augments photocatalytic hydrogen production has been proposed. This strategy, leveraging the synergistic interaction between h-BN and ZnIn2S4, is anticipated to be applicable to other semiconductor systems, opening avenues for the advancement of photocatalytic technologies.

Acousto-Drag Photovoltaic Effect by Piezoelectric Integration of Two-Dimensional Semiconductors.

Light-to-electricity conversion is crucial for energy harvesting and photodetection, requiring efficient electron-hole pair separation to prevent recombination. Traditional junction-based mechanisms using built-in electric fields fail in nonbarrier regions. Homogeneous material harvesting under a photovoltaic effect is appealing but is only realized in noncentrosymmetric systems via a bulk photovoltaic effect. Here we report the realization of a photovoltaic effect by employing surface acoustic waves (SAWs) to generate zero-bias photocurrent in the conventional layered semiconductor MoSe2. SAWs induce periodic modulation to electronic bands and drag the photoexcited pairs toward the traveling direction. The photocurrent is extracted from a local barrier. The separation of generation and extraction processes suppresses recombination and yields a large nonlocal photoresponse. We distinguish the acousto-electric drag and electron-hole pair separation effect by fabricating devices of different configurations. The acousto-drag photovoltaic effect, enabled by piezoelectric integration, offers an efficient light-to-electricity conversion method, independent of semiconductor crystal symmetry.

Degradation performance and mechanism of VOCs in asphalt by alkali metal-doped La2Ce2O7-based fluorite through pyroelectric and photocatalytic synergy

Under high-temperature construction conditions, the use of asphalt can release a large amount of volatile organic compounds (VOCs), which has adverse effect on the environment and human health. Part of fluorite oxides show potential application in VOCs conversion due to their excellent photoresponse and chemical stability in addition to ferroelectricity, piezoelectricity and pyroelectricity properties. In this paper, La2Ce2O7-based fluorite was modified with alkali metal doping and its photo-thermal coupling catalytic effects on the degradation performance of VOCs in asphalt were investigated. The results show that the fluorite catalysts La1.85A0.15Ce2O7 (A=Li, Na, K, Rb, Cs) have efficient electron-hole pair separation ability. Among them, the Rb+ doped La2Ce2O7 sample not only has stronger pyroelectric effect due to increased lattice distortion and oxygen vacancies, but also has the best photogenerated charge transport property and more favorable valence band position for oxidation reaction. Under the photo-thermal synergistic effect, the catalytic degradation performance of VOCs in asphalt by Rb+ doped La2Ce2O7 catalyst can reach 82.61 % at 50 min. Additionally, dynamic shear rheological tests indicate that the addition of catalysts at this blending ratio can enhance the rutting resistance of the asphalt material. This study introduces an innovative approach to enhance the efficiency of multi-field coupled degradation processes of volatile organic compounds (VOCs) in asphalt.

Facile synthesis of NH2-MIL-53(Al)@BiOBr@CQDs ternary heterostructure photocatalyst for degradation of ciprofloxacin in water

The construction of ternary heterojunction photocatalysts can achieve multi-gradient transfer of charges and accurate control the position of photogenerated electrons which has received increasing attention. In this paper, NH2-MIL-53(Al)@BiOBr@CQDs-10 % (ABCQDs-10 %) was prepared via a facile hydrothermal and chemical synthesis processes. Three-dimensional serration of NH2-MIL-53(Al) as a platform for irregular BiOBr nanosheets, CQDs promote interfacial contact and act as electron transport channels between BiOBr and NH2-MIL-53(Al) and constitute Z-type heterojunctions with high redox properties. ABCQDs-10 % shows the best photocatalytic removal efficiency (94.24 %) of CIP, the reaction rate constants (0.045 min−1) were 1.2 and 64 times higher than BiOBr and NH2-MIL-53(Al), respectively. The excellent degradation performance is attributed to the construction of Z-type heterojunction of NH2-MIL-53(Al)@BiOBr@CQDs which improve electron-hole separation and transfer efficiency. The main active species was •O2-. The photocatalytic activity of ABCQDs-10 % had not obvious loss after cycle experiments and the crystal structure had no significant changes, means high stable photocatalytic activity.

Modified Ta2O5-x prepared by NaBH4 reduction for enhance its photocatalytic activity

The generation of oxygen vacancies assumes a pivotal role in the photocatalytic degradation of antibiotics. Surface oxygen vacancies serve as deterrents to the recombination of photogenerated carriers, thereby augmenting photocatalytic efficiency. In this work, the NaBH4 reduction technique was adopted to introduce oxygen vacancies onto the surface of Ta2O5-x, thus enhancing its photocatalytic powers. Remarkably, the photocatalytic activity of the modified Ta2O5-x-0.5 M samples exhibited significant improvement upon treatment with NaBH4 solution at varied concentrations. Characterization of the modified Ta2O5-x samples was conducted using a suite of techniques including XRD, FT-IR, UV–vis DRS, ESR, XPS, and EPR. Notably, the EPR spectrum provided compelling evidence of the presence of oxygen vacancies, affirming their existence on the surface of the modified Ta2O5-x samples. To further corroborate the formation of oxygen vacancies, tetracycline (TC) solution was employed as a simulated pollutant, revealing a marked enhancement in visible light catalytic activity through experimental observations. The findings elucidate that the defect sites engendered by oxygen vacancies primarily enhance the efficiency of electron-hole pair separation and facilitate greater absorption of visible light, thereby amplifying photocatalytic activity. The modification of Ta2O5-x samples by NaBH4 reduction predominantly facilitates the introduction of oxygen vacancies on the surface, consequently bolstering photocatalytic performance. This exemplifies a noteworthy approach for significantly enhancing the photocatalytic activity of Ta2O5-x, providing valuable insights for future design strategies.

Synthesis of carbon nitride nanosheets with N vacancies boosted by S doping for photocatalytic efficient killing of E. coli under visible light

To address the problem of bacterial contamination in drinking water, we synthesized non-metallic photocatalysts for the inactivation of Escherichia coli in drinking water. In this paper, S-g-C3N4 (S-g-CN) composite nanomaterials were synthesized via a one-step calcination method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and transmission electron microscopy (TEM) analyses confirmed the successful synthesis of S-g-CN with N vacancies. Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy analyzed the layered morphology and chemical structure of g-C3N4 before and after modification. Optical characterization revealed significantly enhanced light absorption, electron-hole separation efficiency, and carrier mobility in the modified samples. Bactericidal assays demonstrated that under visible light, 0.3 % S-g-CN nanomaterials exhibited superior bactericidal effects against E. coli compared to unmodified g-C3N4. Furthermore, 0.3 % S-g-CN demonstrated excellent degradation of Rhodamine B (RhB) under various conditions (pollutant concentration, pH, and catalyst dosage). Recyclability studies over three cycles confirmed the catalyst's stability and reusability.

Nanofibrous La0.95K0.05MnO3 perovskite with improved photoelectrical properties for photocatalytic degradation of antibiotics

Potassium doped lanthanum manganese perovskite oxides, La1−xKxMnO3, with nanofibrous structure, are prepared and used for Photo-Fenton degradation of antibiotics, including ciprofloxacin (CIP), tetracycline (TC), and sulfathiazole (ST). Effects of K doping on the textural structure, optical property, band gap and surface chemistry of LaMnO3 are investigated, showing that La0.95K0.05MnO3 (LKMO-5) has the optimal properties. The photoelectric measurements, including photoluminescence (PL), photocurrent response (PCR) and electrochemical impedance spectroscopy (EIS), also suggest that the LKMO-5 has the best electron–hole separation efficiency, the most amounts of irradiated electrons and the lowest impedance. Photocatalytic tests indicate that LKMO-5 not only shows the best activity for CIP degradation, but also exhibits good stability in the reaction, with negligible activity loss within four cycles. Mechanism investigations, explored by the radical trapping experiments and with the reference of band positions, indicate that superoxide radical ions (·O2−) and holes (h+) are the major reactive species of the reaction.

PVP-assisted in-situ self-assembly hierarchical BiOCl with oxygen vacancies for efficient photocatalytic oxidation of cyclohexane under air in solvent-free conditions

Cyclohexane (CHA) selective oxidation reactions are crucial in designing advanced organic intermediates but suffering from very challenges as the products of KA oil (cyclohexanol and cyclohexanone) are more readily oxidized to CO2. Herein, we report that a polyvinylpyrrolidone (PVP) coating of fluffy self-assembled morphology of BiOCl by nanosheets with exposed {001} facets are synthesized via the solvothermal method. Moreover, the as-synthesized hierarchical BiOCl exhibits a significant presence of in-situ produced oxygen vacancies during photocatalysis, thereby facilitating efficient CHA oxidation to KA oil with air as an oxidant in solvent-free at room temperature. The crystallinity, micromorphology, and electronic structure of BiOCl can be significantly influenced by the concentration of NH4Cl and PVP. In the photocatalytic oxidation, oxygen vacancies act as traps to inhibit electrons and holes recombination and adsorb-activate the oxygen molecule, producing h+ and ·O2− radical to achieve 466.7 μmol of KA oil (340.8 μmol of cyclohexanone and 125.9 μmol of cyclohexanol) with a selectivity of 93.9 %. The ∙OH radicals play a predominant role in the production of CHA-one. After conducting 5 experimental cycles, a consistent yield of 92 % towards KA oil and unchanged selectivity can still be maintained. The excellent photocatalytic performance can be attributed to the enhanced photo-absorption and narrow energy gap, abundant oxygen vacancies, high exposed {001} facets, smaller size and large specific surface area, and efficient electron-hole separation. The present work sheds light on the synergistic effect of PVP coating and in-situ formed oxygen vacancies on enhancing photocatalytic activity of Bi-based materials.

Nanoengineering construction of g-C3N4/Bi2WO6 S-scheme heterojunctions for cooperative enhanced photocatalytic CO2 reduction and pollutant degradation

S-scheme heterojunction photocatalysts featuring efficient charge transport paths provide a promising strategy for cooperative achieving photocatalytic CO2 reduction reaction (CO2RR) and Rhodamine B (RhB) degradation. In this work, S-scheme heterojunctions composed of g-C3N4 nanosheets coated on Bi2WO6 nanosheets were prepared by a one-step hydrothermal method, resulting in broad-spectrum light absorption, high electron–hole separation efficiency, and excellent photocatalytic CO2 reduction and RhB oxidization performance. Mechanistic analysis revealed the formation of a directional charge transport path at the interface of the heterojunction, which maintained a high oxidation and reduction potential and improved the efficiency of photoexcited carrier separation. In particular, the synergistic reaction system showed excellent photoredox activity compared with the two separate half-reactions. The optimal catalyst 15CN/BWO displayed the highest CO2 conversion efficiency, with CO and CH4 generation rates of 4.3 and 2.7 μmol g−1h−1, respectively, and the degradation efficiency of the composite heterojunction was significantly higher than that of its constituent materials. This work provides a new possibility for designing a novel dual-function photocatalytic reaction system.

Robust Covalent Organic Frameworks for Photosynthesis of H2O2: Advancements, Challenges and Strategies.

Since 2020, covalent organic frameworks (COFs) are emerging as robust catalysts for the photosynthesis of hydrogen peroxide (H2O2), benefiting from their distinct advantages. However, the current efficiency of H2O2 production and solar-to-chemical energy conversion efficiency (SCC) remain suboptimal due to various constraints in the reaction mechanism. Therefore, there is an imperative to propose efficiency improvement strategies to accelerate the development of this reaction system. This comprehensive review delineates recent advances, challenges, and strategies in utilizing COFs for photocatalytic H2O2 production. It explores the fundamentals and challenges (e.g., oxygen (O2) mass transfer rate, O2 adsorption capacity, response to sunlight, electron-hole separation efficiency, charge transfer efficiency, selectivity, and H2O2 desorption) associated with this process, as well as the advantages, applications, classification, and preparation strategies of COFs for this purpose. Various strategies to enhance the performance of COFs in H2O2 production are highlighted. The review aims to stimulate further advancements in utilizing COFs for photocatalytic H2O2 production and discusses potential prospects, challenges, and application areas in this field.

Improving charge separation capability of CdS/Bi/Ti3C2Tx nanocomposites for efficient photocatalytic oxidative organic transformations

The development of new strategies to improve the separation of photogenerated carriers is crucial for enhancing photocatalytic efficiency of heterogeneous photocatalysts. Here, we have successfully constructed CdS/Bi/Ti3C2Tx nanocomposites with high electron-hole separation efficiency through coupling Bi and Ti3C2Tx on CdS nanorods. The average emission lifetime of the CdS/Bi/Ti3C2Tx nanocomposites can be up to ca. 6.74 ns, which realizes efficient heterogeneous photocatalysis for oxidative hydroxylation of arylboronic acids and coupling of amines with high yields. The photocatalytic rates are ∼15250 μmol·g−1·h−1 for 4-cyanophenol production and ∼12125 μmol·g−1·h−1 for (E)-N-benzyl-1-phenylmethanimine production, which are twice and three-fold higher than those (∼7500 and ∼4000 μmol·g−1·h−1) of the CdS nanorods, respectively. The high photocatalytic efficiency can be ascribed to the strong electron-hole separation capacity by migrating electrons into Bi and Ti3C2Tx from CdS nanorods. In addition, the CdS/Bi/Ti3C2Tx nanocomposites also have satisfactory sustainable recycling and reuse properties. This work provids a new strategy for constructing heterogeneous metal/semiconductor nanophotocatalysts with strong electron-hole separation capacity for high-efficient light-driven organic transformations.

Photoelectrocatalytic efficiency of In2S3–In2O3 films as photoelectrodes/photocatalyst in hydrogen production reaction

In2S3–In2O3 films were used as photoelectrodes and photocatalysts for hydrogen production. The films were grown using a hydrothermal method for different reaction times (4, 6, 8, 12, 18 and 24h). The difference in the reaction time influences the presence of other crystalline phases, such as β-In2S3, In2O3, Ti3S4, and Ti5S8, on the film structure; the presence of these elements was verified by the XPS results. Furthermore, the mixture of phases generates different morphologies such as flowers, pyramids, and sheets. The best photoelectrochemical results were obtained from the films deposited at a reaction time of 6, 8, and 12 h, as these films have an OCP value of ∼0.3586, 0.3791 and 0.4771 VRHE and a photocurrent density of 3, 1.92, and 1.5 μA•cm−2 at 1.23 V vs. RHE, respectively. According to these results, the 12h/In2S3–In2O3 film has the highest donor density and the lowest Debye length, which enhances the efficiency of photogenerated electrons and electron-hole separation. Moreover, the highest photocatalytic hydrogen production was achieved with the 12h/In2S3–In2O3 film, which, in addition to presenting the most optimal photoelectrochemical properties, also has defects such as oxygen deficiencies, Ini and VIn, which could act as traps for electrons in the recombination process, increasing the reduction reactions at low energy and enhancing hydrogen production.

Highly dispersed BiVO4 nanoparticles supported by pseudoboehmite for effective removal of antibiotics

BiVO4/pseudoboehmite (PB) composite catalysts were innovatively prepared using the cost-effective PB as support by a facile hydrothermal method. BiVO4 nanoparticles with an average size of 12 nm are highly dispersed on the surface of PB. Compared to pure BiVO4, the composite BiVO4/6 %PB exhibits high specific surface area (32.9 m2/g) about double that of pure BiVO4 (15.1 m2/g) which can provide more adsorption and photocatalytic reaction sites. Meanwhile, the composite has enhanced photogenerated electron-hole separation and transfer efficiency. As a result, it has a superior performance of antibiotics removal in water than pure BiVO4. The tetracycline hydrochloride (TCH) removal efficiency of BiVO4/6 %PB can reach 87 % within 2 h with high stability (<7 % decay after four cycles) under LED lamp (380–780 nm) irradiation as well as high selectivity. Specifically, the adsorption efficiency and photocatalytic rate constant are respectively triple and double that of pure BiVO4. Simultaneously, the BiVO4/6 %PB also possesses high removal efficiency of amoxicillin (76 %). Our results indicate that the selection of cost-effective PB as catalyst support offers a new solution to solve the aggregation problem of BiVO4 nanoparticles and the composite obtained contributes to an economic and efficient BiVO4-based photocatalyst for antibiotics removal in sewage treatment.

Photocatalytic performance of water-soluble nucleobase-functionalized molybdenum disulfide nanocomposite against methyl blue dye

This report indicates the applicability of an ecofriendly and low cost modified MoS2 nanocomposite as photocatalytic degradation of organic dye from wastewater. The synthesized MoS2 nanocomposite, specifically the Cy-80 % and E-MoS2, demonstrated a high photodegradation efficiency of methyl blue dye in wastewater under UV light irradiation. The incorporation of a nucleobase-containing polymer within the MoS2 structure led to enhanced photocatalytic performance by creating separate wide surface areas and abundant active sites for efficient electron-hole pair separation. The obtained nanocomposite showed superior degradation efficiency compared to aqueous phase exfoliated MoS2 alone (75.6 %), with a photodegradation efficiency of up to 98.7 % within 60 min of UV light irradiation. Furthermore, the Cy-PPG modified MoS2 nanocomposite exhibited significant degradation efficiency over multiple cycles, making it a promising material for the degradation of dye-containing wastewater using visible irradiation sources.

Visible-light-driven Z-scheme La-MOF/BiOBr heterojunction for the efficient removal of rhodamine B and hexavalent chromium from wastewater

Addressing the formidable challenge of treating significant quantities of organic dyes and heavy metal chromium in tannery wastewater, this study synthesized a novel Z-scheme La-MOF/BiOBr composite heterojunction photocatalyst via the hydrothermal method and established an efficient visible-light photocatalytic system. To comprehensively evaluate the photocatalytic redox activity, rhodamine B (RhB) and heavy metal Cr(VI) were selected as target pollutants. Kinetic analysis revealed that the optimal LM-BB-50 catalyst achieved over 99 % degradation of RhB and Cr(VI) within 15 min illumination, indicating the remarkable enhancement of Z-scheme heterojunction in photocatalytic oxidation and reduction efficiency. Based on various photoelectric analysis techniques, it was elucidated that the superior activity of the Z-scheme heterojunction originated from the modulation of the band structure upon La-MOF and BiOBr integration, significantly improving visible light absorption, electron-hole pair separation efficiency, and endowing the energy band with robust redox capabilities. Free radical capture and quenching experiments confirmed that photogenerated holes and superoxide radicals played a crucial role in RhB oxidation, while photogenerated electrons were the primary active species for Cr(VI) reduction.

Innovative Bi5O7I/MIL-101(Cr) Compounds: A Leap Forward in Photocatalytic Tetracycline Removal.

In environmental chemistry, photocatalysts for eliminating organic contaminants in water have gained significant interest. Our study introduces a unique heterostructure combining MIL-101(Cr) and bismuth oxyiodide (Bi5O7I). We evaluated this nanostructure's efficiency in adsorbing and degrading tetracycline (TC) under visible light. The Bi5O7I@MIL-101(Cr) composite, with a surface area of 637 m2/g, prevents self-aggregation seen in its components, enhancing visible light absorption. Its photocatalytic efficiency surpassed Bi5O7I and MIL-101(Cr) by 33.4 and 9.2 times, respectively. Comprehensive analyses, including scanning electron microscopy (SEM) and transmission electron microscopy (TEM), confirmed the successful formation of the heterostructure with defined morphological characteristics. BET analysis demonstrated its high surface area, while X-ray diffraction (XRD) confirmed its crystallinity. Electron spin resonance (ESR) tests showed significant generation of reactive oxygen species (ROS) like h+ and·•O2- under light, crucial for TC degradation. The material maintained exceptional durability over five cycles. Density functional theory (DFT) simulations and empirical investigations revealed a type I heterojunction between Bi5O7I and MIL-101(Cr), facilitating efficient electron-hole pair separation. This study underscores the superior photocatalytic activity and stability of Bi5O7I@MIL-101(Cr), offering insights into designing innovative photocatalysts for water purification.