Photogenerated Charge Separation Research Articles

The use of green synthesized TiO2/MnO2 nanoparticles in solar power membranes for pulp and paper industry wastewater treatment

The pulp and paper manufacturing wastewater is as complicated as any other industrial effluent. A promising approach to treating water is to combine photocatalysis and membrane processes. This paper demonstrates a novel photocatalytic membrane technique for solar-powered water filtration. The method is based on creating green-prepared TiO2, and MnO2 nanoparticles (NPs) using Pomegranate peels and Seder leaf extracts and incorporation into polyvinylidene chloride to produce a novel water purification system that combines semiconductor photocatalysis with membrane filtration. The prepared heterostructure of the TiO2/MnO2 nanocomposite membrane provides photogenerated charge separation. To ensure chemical bonding at the membrane surface, Raman and Fourier transform infrared spectroscopy (FT-IR) were employed. The modified membrane’s hydrophilicity and roughness increased significantly. Additionally, the modified nanocomposite membrane’s porosity was measured. The integrated process demonstrated much higher removal of humic acid and high efficiency of wastewater treatment for pulp and paper. In sunlight, humic acid removal was 98% from synthetic wastewater. While using the produced membrane on pulp and paper effluent, these studies indicate that: in the dark, the removal was 50%, while in the sunlight, the removal increased to 70%, with a reduction in the COD from 1500 mg/L to 247 mg/L. Additionally, the TDS decreased from 1630 to 452 ppt in the sunlight. This research sheds light on how solar energy can clean wastewater from the pulp and paper industry while improving membrane separation. Also, an alternative source to sunlight was used to manufacture a photocatalytic membrane with high efficiency for wastewater treatment and an inexpensive price.

Tuning surface hydrophilicity of a BiVO4 photoanode through interface engineering for efficient PEC water splitting.

This study presents a novel approach to enhance photoelectrochemical (PEC) water oxidation by integrating cobalt phthalocyanine (CoPc) with bismuth vanadate (BVO) via a direct solvothermal method. The as-prepared BVO@CoPc photoanode demonstrated a photocurrent density of 4.0 mA cm-2 at 1.23 V vs. RHE, which is approximately 3.1 times greater than that of the unmodified BVO, and has superior stability. The incident photon-to-current conversion efficiency (IPCE) of the BVO@CoPc photoanode reaches an impressive value of 81%, accompanied by significant enhancements in charge injection efficiency. This excellent performance can be ascribed to the enhanced hydrophilicity with the BVO/CoPc interface engineering, which facilitates interfacial interaction between the electrode and electrolyte, accelerates photogenerated charge carrier transfer and separation. Furthermore, compared to the immersion and drop-casting methods, the BVO@CoPc-S composite photoanode prepared via the solvothermal method exhibits a significant improvement in interfacial contact and surface hydrophilicity. These findings highlight the potential of the strategy based on interfacial hydrophilicity modification to overcome key limitations in PEC water splitting, providing a pathway to more efficient and durable photoanode design.

Construction of Covalent Triazine Framework With D‐A1‐A2 Configuration via Post‐Modification for Photocatalytic Hydrogen Evolution

ABSTRACTA D‐A1‐A2 type covalent triazine framework (CTF) was prepared for the photocatalytic hydrogen evolution (HER). In the resulting CTF‐CZ‐Bpy2+, 9‐ethyl‐9H‐carbazole (CZ) group is used as the donor, triazine ring as the first acceptor, and cyclic diquat (Bpy2+) moiety as the second acceptor. Both experimental and theoretical results show that the D‐A1‐A2 structure significantly enhances the efficiency of photogenerated charge separation and transfer. As a result, CTF‐CZ‐Bpy2+ demonstrated outstanding photocatalytic HER activity with a yield rate of 31.1 mmol g−1 h−1, which is 7.8 times higher than that of nonfunctionalized CTF‐CZ‐Bpy.

Diacetylene-bridged covalent organic framework as crystalline graphdiyne analogue for photocatalytic hydrogen evolution.

Graphdiyne (GDY) alone as a photocatalyst is unsatisfactory because of its low crystallinity, limited regulation of the band gap, weak photogenerated charge separation, etc., and heterojunctioning with other materials is necessary to activate the photocatalytic activity of GDY. Through elaborate design, a diacetylene-rich linker (S2) was prepared and employed to construct a crystalline and structurally well-defined GDY-like covalent organic framework (COF, namely S2-TP COF) which merges the merits of both COF and GDY to boost the photocatalytic hydrogen evolution reaction (HER). By theoretical prediction on the donor-acceptor (D-A) pair, two other monoacetylene-bridged COFs (S1-TP COF and S3-TP COF) were prepared for comparison. Exhibiting enhanced separation and suppressed recombination of photogenerated excitons, Pt-photodeposited S2-TP COF showed a higher HER rate (10.16 mmol g-1 h-1) than the other two non-GDY-like COFs (3.71 and 1.13 mmol g-1 h-1). A joint experimental-theoretical study suggests that the appropriate D-A structure for photogenerated charge separation and diacetylene motif as the adsorption site are the key reasons for the boosted HER. This work opens a new avenue for the rational design of COFs as GDY mimics for photocatalytic application.

Enhanced degradation of levofloxacin using photocatalysis and peroxymonosulfate oxidation processes by Z-scheme BiVO4/g-C3N4 heterojunction

Constructing a direct Z-scheme heterostructure is an effective way to improve photogenerated charge separation efficiency. In this work, a novel BiVO4/g-C3N4 (BVO/CN) Z-scheme heterojunction was successfully fabricated through a liquid film combustion method and ultrasonic desperation technique. The obtained samples were analyzed by serials characterization techniques, such as XRD, FT-IR, XPS, SEM, HRTEM, EDS, BET, UV-vis, and PL. The results demonstrated a strong integration between CN and BVO, as evidenced by the absorption edge shifting to 520nm and revealing a narrow band gap (Eg=2.47eV), thereby enhancing light absorption capacity. Under visible light irradiation, the removal efficiency of levofloxacin (LVFX) reached 97.7% within 40min using 20 BVO/CN, which was respectively 2.03 and 2.21 times higher than that achieved with BVO or CN alone. The mechanism of the BVO/CN Z-scheme heterojunction was elucidated based on the ESR test and radical trapping experiment. Additionally, the potential degradation pathway of LVFX was analyzed using HPLC-MS. This study demonstrates the feasibility of constructing a Photocatalyst/Visible-light/peroxymonosulfate (PMS) system for mitigating antibiotic-induced ecological pollution.

Donor–Acceptor Structure Induced Long‐Persistent Luminescence and Application in Temperature Measurement at Cryogenic Environment

AbstractWith the development and application of cryogenic technology, the demand for temperature measurement in cryogenic environment is increasing. Optical sensing can provide a non‐contact method of temperature measurement in cryogenic environments. Herein, a new temperature measurement route based on the persistent luminescence is proposed. The single‐component, coordination crystal Zn‐ddcphpy with electron donor and acceptor structures, achieving persistent luminescence (6–7 s) after irradiating by ultraviolet light source at 80 K. The persistent luminescence decay and electron paramagnetic resonance show that the reason for the persistent luminescence generation is the photogenerated charge separation and recombination. In cryogenic environment controlled by liquid nitrogen (80–260 K), the persistent luminescence duration decreases with increasing temperature, the color gradually changes from green to yellow with the spectrum red‐shift. Taking Zn‐ddcphpy as a model material, the unquiet temperature sensitive based persistent luminescence shows convenience, intuitive and inexpensive. Furthermore, the LPL (long‐persistent luminescence) of Zn‐ddcphpy exhibits high sensitivity and responsiveness to temperature at cryonic environment, make it suitable for temperature measurement on real time. In this work, the change of duration and color can indicate temperature without contact, which can be used for temperature measurement and monitoring in the fields of cryogenic wind tunnels, cold chain storage, etc.

Predesign of Covalent-Organic Frameworks for Efficient Photocatalytic Dehydrogenative Cross-Coupling Reaction.

The dehydrogenative cross-coupling reaction is the premier route for synthesizing important 4-quinazolinone drugs. However, it usually requires high reaction temperature and long reaction time, and the yield of the final product is low. Here two stable and photosensitive covalent-organic frameworks (COFs), TAPP-An and TAPP-Cu-An are purposefully designed and constructed to serve as unprecedented heterogeneous tandem catalysts to complete dehydrogenative cross-coupling reactions in a short time and under mild reaction conditions (room temperature and light), leading to the high-efficient photosynthesis of 4-quinazolinones. Particularly, TAPP-Cu-An is the best heterogeneous catalyst currently available for the synthesis of 4-quinazolinones, even surpassing all the catalysts reported so far. It also enables one-step photosynthesis of 4-quinazolinones with higher conversion (>99%) and selectivity (>99%) in a shorter time, and the product can be easily prepared on a gram scale. Extensive experiments combined with theoretical calculations show that the excellent photogenerated charge separation and transport capability, as well as the synergistic An-Cu catalysis in TAPP-Cu-An are the main driving forces for this efficient reaction.

Engineering n-Type and p-Type BiOI Nanosheets: Influence of Mannitol on Semiconductor Behavior and Photocatalytic Activity.

Photocatalytic technology holds significant promise for sustainable development and environmental protection due to its ability to utilize renewable energy sources and degrade pollutants efficiently. In this study, BiOI nanosheets (NSs) were synthesized using a simple water bath method with varying amounts of mannitol and reaction temperatures to investigate their structural, morphological, photoelectronic, and photocatalytic properties. Notably, the introduction of mannitol played a critical role in inducing a transition in BiOI from an n-type to a p-type semiconductor, as evidenced by Mott-Schottky (M-S) and band structure analyses. This transformation enhanced the density of holes (h+) as primary charge carriers and resulted in the most negative conduction band (CB) position (-0.822 V vs. NHE), which facilitated the generation of superoxide radicals (·O2-) and enhanced photocatalytic activity. Among the samples, the BiOI-0.25-60 NSs (synthesized with 0.25 g of mannitol at 60 °C) exhibited the highest performance, characterized by the largest specific surface area (24.46 m2/g), optimal band gap energy (2.28 eV), and efficient photogenerated charge separation. Photocatalytic experiments demonstrated that BiOI-0.25-60 NSs achieved superior methylene blue (MB) degradation efficiency of 96.5% under simulated sunlight, 1.14 times higher than BiOI-0-70 NSs. Additionally, BiOI-0.25-60 NSs effectively degraded tetracycline (TC), 2,4-dichlorophenol (2,4-D), and rhodamine B (Rh B). Key factors such as photocatalyst concentration, MB concentration, and solution pH were analyzed, and the BiOI-0.25-60 NSs demonstrated excellent recyclability, retaining over 94.3% of their activity after three cycles. Scavenger tests further identified ·O2- and h+ as the dominant active species driving the photocatalytic process. In this study, the pivotal role of mannitol in modulating the semiconductor characteristics of BiOI nanomaterials is underscored, particularly in promoting the n-type to p-type transition and enhancing photocatalytic efficiency. These findings provide a valuable strategy for designing high-performance p-type photocatalysts for environmental remediation applications.

Polarization-Induced Internal Electric Field-Dominated S-Scheme KNbO3-CuO Heterojunction for Photoreduction of CO2 with High CH4 Selectivity.

The polarization-induced internal electric field (IEF) in ferroelectric materials could promote photogenerated charge transfer across the heterojunction interface, but the effect of polarization-induced IEF on the mechanism of photogenerated charge transfer is ambiguous. In this study, a KNbO3-CuO heterojunction was synthesized by depositing copper oxide (CuO) onto KNbO3. Incorporating CuO broadens the light absorption of KNbO3, thereby enhancing the dissociation of the photogenerated charges. The results show that the polarization-induced IEF in KNbO3 determines that the charge transport mechanism in the KNbO3-CuO heterojunction follows the S-scheme. Owing to the S-scheme heterojunctions and efficient CO2 capture and activation by CuO, the CH4 production rate of KNbO3-CuO increased by nearly 26 times compared to KNbO3. Additionally, the CH4 selectivity of KNbO3-CuO could reach up to 97.80%. This research offers valuable insights into enhancing the photogenerated charge separation and constructing heterojunctions.

Low-valence platinum single atoms in sulfur-containing covalent organic frameworks for photocatalytic hydrogen evolution

This study focuses on optimizing catalytic activity in photocatalytic hydrogen evolution reaction by precisely designing and modulating the electronic structure of metal single atoms. The catalyst, denoted as PtSA@S-TFPT, integrates low-valence platinum single atoms into sulfur-containing covalent organic frameworks. The robust asymmetric four-coordination between sulfur and platinum within the framework enables a high platinum loading of 12.1 wt%, resulting in efficient photocatalytic hydrogen production activity of 11.4 mmol g−1 h−1 and stable performance under visible light. These outcomes are attributed to a reduced hydrogen desorption barrier and enhanced photogenerated charge separation, as indicated by density functional theory calculations and dynamic carrier analysis. This work challenges traditional notions and opens an avenue for developing low-valence metal single atom-loaded covalent organic framework catalysts to advance photocatalytic hydrogen evolution.

Carbon-dot-induced oxygen vacancies in copper vanadate enabling persulfate photoactivation for tetracycline degradation.

Synchronously creating oxygen vacancies (OVs) and an internal electric field (IEF) in photocatalysts could be an ideal strategy to facilitate photogenerated charge separation and surface reactions but remain unexplored for this use. In this work, we report that low-cost and multifunctional CDs can involve in the nucleation reaction of copper vanadates (CuVs) to create OVs and proper IEF at the interface by modulating the valence states of coppers under hydrothermal conditions. Thus, CDs synergistically serve as oxygen vacancy inducer and charge separator in CuVs to extract photogenerated carriers to trigger persulfate (PS) activation for the degradation of tetracycline hydrochloride (TC). It turns out that CDs-modulated CuVs exhibit the expected photocatalytic capacity to activate PS in water and enable TC decomposition efficiency approximately 8 times higher than CDs-free CuVs under visible light irradiation. Our investigations elucidate that the oxidative breakdown of TC is dominated by the active species cooperation of 1O2 with h+ and OH formed in photocatalytic reaction system.

Dynamic proton migration in dual linkage-engineered D-π-A system for photosynthesis H2O2 generation

Accelerated charge migration and proton transfer to the reaction site are critical factors for improving photocatalytic efficiency. However, realizing both simultaneously is challenging because of the sluggish water (proton source) oxidation kinetics and interdependent redox reactions. Herein, we design an imide and hydrogen bond to connect carbon nitride ports of the D-π-A system with the dual-engineered linkages. The system uses an acetylene functional group and an imidazole ring as spatially separated water oxidation and oxygen reduction reaction (ORR) catalytic centers for photogenerated charge separation, respectively. The imine bond is a bridge grafted to the oxidation site to act as a hydrogen proton trap, and the hydrogen bond formed between reduction site and carbon nitride is used as the channel for instantaneous proton delivery to the reduction center. In situ characterization confirms that the linking sites protonation optimizes the pathway of ORR to H2O2 and facilitates the *OOH intermediates generated. It is concluded that proton transport plays a critical role in optimizing photocatalytic H2O2 production. Our work provides a strategy to improve dynamic proton transfer mechanisms.

In situ construction of η-Fe2O3/g-C3N4 Z-scheme heterojunction on nickel foam with efficient interfacial charge transport for enhanced photodegradation of Rhodamine B

The design of efficient, low cost and recyclable photocatalyst is of great significance for disposing organic wastewater. In this work, η-Fe2O3/g-C3N4 heterostructure was constructed by in-situ cyclic voltammetry codeposition and calcination on nickel foam (NF). The microstructural and morphological characterization of the sample confirmed that spherical η-Fe2O3/g-C3N4 nanocomposites were co-deposited on three-dimensional porous NF to form Fe2O3/g-C3N4/NF photoelectrode under 50 cycles of 50 mV/s electric field. The removal rate of as-prepared η-Fe2O3/g-C3N4/NF photoelectrode for 10 mg·L−1 Rhodamine B solution reaches 95.2 % in 1h, which is 5.6 times of g-C3N4/NF and 5.3 times of η-Fe2O3/NF, respectively. According to the electrochemical test results, the enhanced photocatalytic activity of η-Fe2O3/g-C3N4/NF was principally due to efficient photogenerated charge separation and transfer ability of the photoelectrode. The results of active species capture experiments indicate that superoxide radical, hydroxyl radical and hole almost equivalently participated in photodegradation of η-Fe2O3/g-C3N4/NF, and its possible photodegradation mechanism was proposed on the basis of Z-scheme charge transport path. The η-Fe2O3/g-C3N4/NF nanocomposites would be expected to become a promising photoelectrode for large-scale applications.

Comparison of different α-Fe2O3 sources in the enhancement of ZnO photocatalytic activity during the degradation of a mixture of endocrine-disruptors

α-Fe2O3/ZnO composites were synthesized using MOF235(Fe), NH2–MOF235(Fe), and FeOOH as α-Fe2O3 precursors via microwave-assisted precipitation and post-calcination at 450 °C. Thermogravimetric analyses (TGA), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), N2 physisorption analysis, scanning electron microscopy using a fully integrated EDS detector (SEM–EDS), X-ray photoelectron spectroscopy (XPS), and electrochemical experiments were employed to characterize the prepared materials. The coupling of MOF235(Fe)-, NH2–MOF235(Fe)-, and FeOOH-derived α-Fe2O3 into ZnO increased the specific surface area values and light absorption in the visible region of ZnO. The NH2–MOF235(Fe)-derived α-Fe2O3/ZnO allowed enhanced photogenerated charge separation with retarded e−/h+ recombination rate and reduced charge-transfer resistance, promoting superior photocatalytic activity. The photocatalytic activity of α-Fe2O3/ZnO composites was evaluated in the degradation of bisphenol A, 4-tert-butylphenol, and 4-tert-octylphenol mixture solution at pH 7.0 under simulated solar light using 0.5 g L−1 catalyst loading. The mineralization percentages of endocrine-disrupting compounds (EDCs) of 36.76%, 42.25%, and 19.92% occurred in 330 min (600 kJ m−2 of accumulated energy) for MOF235(Fe)-, NH2–MOF235(Fe)-, and FeOOH-derived α-Fe2O3/ZnO, respectively. The QSAR approach using the ECOSAR program to evaluate the acute toxicity of the by-products generated with the NH2–MOF235(Fe)_α-Fe2O3/ZnO photocatalyst showed that the effluent was nontoxic for the three target trophic models (fish, Daphnia, and green algae). This result was consistent with those of the Vibrio fischeri bioluminescence inhibition assay, where the effluents using NH2–MOF235(Fe)_α-Fe2O3/ZnO were classified as nontoxic. Thus, NH2–MOF235(Fe) can be successfully used as an α-Fe2O3 precursor to generate an α-Fe2O3/ZnO composite, which is a promising material for removing EDCs from aqueous solutions.

S-Scheme Interface Between K-C3N4 and FePS3 Fosters Photocatalytic H2 Evolution.

In photocatalysis, photogenerated charge separation is pivotal and can be achieved through various mechanisms. Building heterojunctions is a promising method to enhance charge separation, where effective contact and charge exchange between heterojunction components remains challenging. Mostly used synthesis processes for making heterostructures require high temperatures, difficult processes, or expensive materials. Herein, a heterojunction of potassium intercalated graphitic carbon nitride (K-CN) and nanoflakes of iron phosphor trisulfide (FPS) is designed via a simple mechanical grinding process to boost the hydrogen evolution by a factor of more than 25 compared to pure K-CN. This significant improvement is rarely reached by other combinations of two semiconductors without cocatalysts, such as platinum. It can be attributed to the band alignment and band bending of an S-scheme that is validated via optical and X-ray photoelectron spectroscopy. As a consequence, strong quenching of the photoluminescence and significant H2 evolution occur for this unique heterojunction. Furthermore, the excellent durability of the designed photocatalytic heterostructure is confirmed by monitoring the catalysts' H2-evolution rate and crystal structure after 72 h under light illumination. This study opens up promising and simple pathways for constructing efficient S-scheme heterojunctions for photocatalytic water-splitting.

Novel Inorganic-Organic Dual-Photosensitizing Dinuclear-Metal Self-Assembly System for Efficient Artificial Photosynthesis without Sacrificial Electron Donors.

Owing to the unique synergistic effect, dinuclear-metal-molecule-catalysts (DMCs) show excellent performance in catalytic fields. However, for overall photocatalytic CO2 reaction (CO2RR), it is still a challenge to construct well-matched photosensitizer (PS) components for DMCs-based photocatalysts. Inorganic-quantum-dot PS possesses capacities of multiple exciton generation and catalyzing water oxidation but is incompatible with DMCs. In contrast, organic PS can be covalently linked with DMCs but inescapable of using sacrificial electron donors. For overall photocatalytic CO2RR, organic-inorganic dual-photosensitizing system might be a promising candidate. Herein, we employed covalent-linking and electrostatic-driven approaches to construct the self-assembly of pyrene-sensitized Co2L DMCs (Py-Co2L) and perovskite (PVK) quantum dots, i.e., PVK@[Py-Co2L]. Using H2O as an electron donor, PVK@[Py-Co2L] realized 105.24 μmol ⋅ g-1⋅h-1 CO yield in photocatalytic CO2RR, much higher than PVK (15.44 μmol ⋅ g-1⋅h-1) and PVK@Co2L (32.30 μmol ⋅ g-1 ⋅ h-1), ascribing to the efficient photogenerated charge separation and transfer. The experimental results and theoretical investigations demonstrated that the pyrene linked on Co2L boosted the electron delivery from PVK to DMCs. Besides, this strategy could also be extended to the photocatalytic H2 evolution coupled with alcohol oxidation. As a proof-of-concept, our work lightens the integration of DMCs, organic and inorganic PS components, promoting the development of photocatalysis without sacrificial electron donors.

Novel Inorganic‐Organic Dual‐Photosensitizing Dinuclear‐Metal Self‐Assembly System for Efficient Artificial Photosynthesis without Sacrificial Electron Donors

AbstractOwing to the unique synergistic effect, dinuclear‐metal‐molecule‐catalysts (DMCs) show excellent performance in catalytic fields. However, for overall photocatalytic CO2 reaction (CO2RR), it is still a challenge to construct well‐matched photosensitizer (PS) components for DMCs‐based photocatalysts. Inorganic‐quantum‐dot PS possesses capacities of multiple exciton generation and catalyzing water oxidation but is incompatible with DMCs. In contrast, organic PS can be covalently linked with DMCs but inescapable of using sacrificial electron donors. For overall photocatalytic CO2RR, organic–inorganic dual‐photosensitizing system might be a promising candidate. Herein, we employed covalent‐linking and electrostatic‐driven approaches to construct the self‐assembly of pyrene‐sensitized Co2L DMCs (Py‐Co2L) and perovskite (PVK) quantum dots, i.e., PVK@[Py‐Co2L]. Using H2O as an electron donor, PVK@[Py‐Co2L] realized 105.24 μmol ⋅ g−1⋅h−1 CO yield in photocatalytic CO2RR, much higher than PVK (15.44 μmol ⋅ g−1⋅h−1) and PVK@Co2L (32.30 μmol ⋅ g−1 ⋅ h−1), ascribing to the efficient photogenerated charge separation and transfer. The experimental results and theoretical investigations demonstrated that the pyrene linked on Co2L boosted the electron delivery from PVK to DMCs. Besides, this strategy could also be extended to the photocatalytic H2 evolution coupled with alcohol oxidation. As a proof‐of‐concept, our work lightens the integration of DMCs, organic and inorganic PS components, promoting the development of photocatalysis without sacrificial electron donors.

Metal Single Atom-Hydroxyl Incorporation in Poly(heptazine imide) to Create Active Sites for Photocatalytic Water Oxidation.

Poly(heptazine imide) (PHI) salts are extensively researched crystalline carbon nitride photocatalysts, but their photocatalytic water oxidation (PWO) performance is scarcely researched because of the difficulty in creating efficient active sites. Interference of metal ion (e.g., Na+ and K+) loss from the PHI salts in their PWO research has hardly been considered. Herein, metal single atom─OH (e.g., Co─OH) groups are incorporated into PHI to create efficient PWO active sites, via simple ion metathesis, hydrolysis, and deprotonation. The Co─OH modified PHI exhibits 9.3-fold higher PWO (oxygen evolution) activity than PHI, with an external quantum yield reaching 0.44% even at 600 nm. Excluding interference of the metal ion loss, the function of the Co─OH incorporation is evidenced mainly to facilitate the oxygen evolution reaction, as well as to promote photogenerated charge separation and raise visible light absorption, with the role of the OH especially revealed. Moreover, it is discovered that Na+ loss from sodium PHI will decrease its PWO activity, protonation of PHI has a detrimental effect on its PWO performance, and some other metal single atom─OH incorporation in PHI can also enhance its PWO activity. Overall, this work provides a general way to create PWO active sites in PHI.

Boosted photocatalytic degradation performance of TiO2 with enriched oxygen vacancies

In this study, TiO2 with abundant oxygen vacancies (OVs) was prepared through a hydrothermal method in the presence of polyphenylsulphone (PPSU). Introduction of PPSU results in enriched OVs within TiO2 and boosted the level of ∙O2-, dramatically ameliorating photogenerated charges separation efficiency and elevating photocatalytic activity. Compared with the reference TiO2, PPSU-TiO2 exhibits enhance activity in photocatalytic degradation of rhodamine B (RhB) and tetracycline (TC). Analysis reveals that ∙O2- serves as the primary active free radicals in RhB degradation by PPSU-TiO2. Furthermore, PPSU-TiO2 maintains high activity over seven successive cycles, demonstrating excellent stability. Therefore, adding PPSU into the synthesis system of TiO2 is proved to be an effective strategy to enhance photocatalytic performance.

Constructing surface oxygen vacancy in the [Bi2O2]2+ layer defects mediated Bi2MoO6 enhanced visible light responsive photocatalytic activity.

Bi2MoO6 nanospheres with surface oxygen vacancies (SOVs) controlled by the calcination process were prepared in this study. Performance testing revealed that the Bi2MoO6-4 sample (Bi2MoO6 calcined at 350 °C for 4h) with SOVs achieved a remarkable photocatalytic degradation efficiency up to 99.16% for Rhodamine B (RhB) within 50min, which is 2.19 times higher than that of pure Bi2MoO6. The higher photocatalytic performance of the Bi2MoO6-4 sample is attributed to the SOVs' defect level located at the Bi2MoO6 bandgap, narrowing the bandgap to effectively promote the photogenerated charge separation. The promotion of photocarrier separation and electron were transferred due to the Bi-O bond breakage in the Bi2MoO6-4 [Bi2O2]2+ layer, which mediates the defect level of SOVs in the band structure. The density functional theory calculation results reveal the possible formation site of the oxygen vacancy and the vacancy-induced defect states. This study provides a new approach for fabricating new photocatalysts with surface oxygen defects.