Light Absorption Region Research Articles

Preparation of Cu-doped MIL-125(Ti)-derived carbon-based composites for the sonodynamic degradation of organic dyes

Sonocatalysis provides a green and sustainable strategy to remove industrial organic pollutants. Toward improving the sonocatalytic performance to remove the organic dyes, a new Cu-C@TiO2 catalyst was prepared via doping the Cu(II) ions into the MIL-125(Ti) and then carbonizing the resultant Cu-MIL-125(Ti) in this study. By the SEM, EDS and BET, the obtained Cu-C@TiO2 was a porous carbon-based hybrid with bimetallic centers, retaining a large amount of organic frameworks to supply adequate specific surface area for the adsorption; By the XPS and UV–vis DRS, the band gap of Cu-C@TiO2 was reduced to significantly broaden the light absorption region and facilitate the separation of electron-hole pairs; By the fluorescence spectra, the graphite-like structure and Cu particles produced on the catalyst surface served as an electron trap to inhibit the recombination of charge carriers. The Cu-C@TiO2 showed an excellent sonocatalytic performance to organic dyes, and under the ultrasound irradiation (35 KHz, 150 W), it could remove more than 95 % of rhodamine B (5.00 mg/L) and methylene blue (5.00 mg/L) within 10 min. By the kinetic analysis, it was found that the dye removal obeyed the first-order kinetic model, and the scavenging studies of free radicals (OH and O2−) verified the Cu-C@TiO2-mediated sonodynamic degradation was in the dye removal. In the end, a Cu-C@TiO2-mediated adsorption/sonodynamic degradation mechanism was proposed to thermodynamically expound the removal process of organic dyes.

Fabrication of Ag NPs decorated TiO2/WO3 S-scheme heterojunction for efficiently mineralizing gaseous toluene

The energy band structure and corresponding carrier transfer efficiency are crucial roles in photocatalysis performance, especially involving the volatile organic compounds (VOCs) degradation in gas-solid phase photocatalytic systems. Herein, we reported a S-scheme heterojunction photocatalyst of Ag@WO3/TiO2. The photocatalytic experiments display that Ag@WO3/TO2 (denoted as Ag@h-WT) possesses almost 94 % of toluene removal rate and nearly 90 % mineralization after 60 min irradiation under simulated sunlight, superior to those of pure TiO2 and h-WO3 as well as binary WO3/TO2 heterojunction. The improved photocatalytic activity is mainly ascribed to i) the formation of S-scheme heterojunction. ii) The Ag nanoclusters promotes the carrier separation and broadens the light absorption region.

Thienyl-fused dibenzothiophene-S,S-dioxide based conjugated polymer toward highly efficient photocatalytic hydrogen production

Dibenzothiophene-S,S-dioxide (BTDO) is one of the cutting-edge electron-acceptor monomers for designing conjugated polymer based organic materials toward photocatalytic H2 production from water. Normally, structure design of BTDO containing donor-acceptor (D-A) polymer photocatalyst mainly focuses on screening electron-donor motifs, the importance of modification on BTDO molecular toward improving charge carrier separation and photocatalytic performance is always ignored. Herein, a novel thienyl-fused BTDO building block (BTDO-DT) is prepared and utilized to synthesize B-BTDO-DT polymer photocatalyst by Sonogashira-Hagihara cross-coupling polycondensation using 1,4-Diethynylbenzene (B) and BTDO-DT as monomers. Experimental and density functional theory (DFT) calculation results demonstrate that modification of BTDO by thiophene not only enlarges light absorption region and promotes photogenerated e−/h+ separation, but also decreases H atom adsorption free energy (ΔGH*) on oxygen atom in the OSO group. As a result, B-BTDO-DT exhibits an outstanding visible light induced photocatalytic H2 production rate of 156.6 μmol h−1 using 30 mg catalyst without Pt cocatalyst, which is 4.5 times higher than that of B-BTDO. And the H2 production rate of B-BTDO-DT is further improved to be 259.8 μmol h−1 with 2.0 wt% Pt as co-catalyst. The present work may open a new direction for the design of conjugated polymer based photocatalysts with high photocatalytic activities.

Engineering single-atom catalysts on triazine-based covalent organic frameworks for enhanced photocatalytic performance in N2 reduction

The solar conversion of nitrogen to ammonia is a green, sustainable, and promising way to fix nitrogen. However, designing a photocatalyst with high activity, selectivity, and stability for the N2 reduction reaction (NRR) is challenging because of the slow inert activation of N2 and competitive hydrogen evolution reaction (HER). Herein, a single metal site anchored to a triazine-based covalent organic framework (Tr-COF) backbone (named TM@Tr-COF; TM = Fe, Co and Ni) is fabricated for high-performance catalytic N2 reduction. Density functional theory calculations show that the Fe@Tr-COF, Co@Tr-COF and Ni@Tr-COF can effectively activate N2 and reduce it to NH3 via the electron “acceptance–donation” process. Meanwhile, the NRR occurs via the enzymatic pathway on the Fe@Tr-COF, Co@Tr-COF and Ni@Tr-COF with a limiting potential of 0.38 V, 0.58 V and 0.54 V, respectively. Furthermore, the anchoring of Fe/Co/Ni on the Tr-COF allows the Tr-COF to be adjusted to the appropriate edge position and visible light-absorption region, indicating that the system may be a promising and efficient photocatalyst. Compared with other competitive reactions, the system exhibits high selectivity for NH3 production and inhibits competitive HERs. These findings have considerable implications for innovatively designing highly active single-atom catalysts supported by COFs.

A novel recyclable photocatalytic composite TiO2NTs@Bi25FeO40 for tetracycline mineralization

Titanium dioxide nanotubes (TiO2NTs) are prepared by anodizing Ti substrates, which is a good solution to the problem that powdered materials are more difficult to recycle. Hence, a novel recyclable TiO2NTs@Bi25FeO40 (TiO2/BFO) photocatalyst was prepared by anodic oxidation combined with hydrothermal deposition. The photocatalytic ability of TiO2NTs prepared at different factors and Bi25FeO40 compound was evaluated. The TiO2/BFO showed the optimal photocatalytic efficiency, which the removal ratio of tetracycline hydrochloride (TC-HCl) higher than that of TiO2NTs under visible-light irradiation. UV–vis diffuse reflectance spectra (DRS) analysis proved that the band gap of TiO2/BFO was narrower than that of TiO2NTs. The narrow band gap of TiO2/BFO results in a broadening of its light absorption region. Meanwhile, the combination of free radical quenching experiments and EPR measurement showed that ·O2− was the main active radical in the photocatalytic process, and the presence of Bi25FeO40 effectively promoted the generation and transfer of electrons. Mechanistic analysis showed that a unique II-type heterojunction electron transfer structure was formed between TiO2NTs and Bi25FeO40, which promoted the photogenerated electron-hole separation and improved the photocatalytic oxidation activity. The preparation of TiO2/BFO provided a new strategy for synthesizing more efficient and environmentally friendly photocatalyst.

Photo‐Assisted Bifunctional Cathodes with Lower Energy Gap and Broadened Light Absorbing Region for Lithium‐Ion Batteries – Extended Conjugation Through Customization

AbstractHigh‐performance optoelectronic bifunctional cathode materials may simultaneously seize and store solar energy in lithium‐ion batteries to boost their storage capacity. However, such photoactive cathodes with typical intrinsic features are generally limited for UV light applications and offer poor sunlight harvesting which results in lower energy density. Here, the assembly of two oligomers, poly(vat blue 6) (PVB6) and poly(vat blue 6 sulfide) (PVB6S) is reported, through polymerization to extend the conjugated structure of organic optoelectronic small molecules. These oligomers are effectively employed as photo‐assisted bifunctional cathodes for lithium‐ion batteries. The extended conjugated structure narrows the energy gap, promoting exciton dissociation and expanding the light absorption region. PVB6S possesses a narrow energy gap of 1.565 eV, and the discharge‐specific capacity of the battery with PVB6S is enhanced from 203 to 411 mAh g−1 under light illumination, which is approximately twice the original capacity. This demonstrates the extended conjugated structure and charge separation in a cell, which synergistically contributes to the rational design of photo‐assisted bifunctional cathode materials and complementary enhances the performance of lithium‐ion batteries.

Multicolor lignin-derived carbon quantum dots: Controllable synthesis and photocatalytic applications

The cost-effective, high-performance fabrication of multicolor carbon quantum dots (CQDs) from biomass is critical to its prospective application. Lignin, with its phenylpropane structural unit and abundant functional groups, is a reliable precursor for the formation of high-quality CQDs. Here, CQDs from renewable lignin were successfully prepared via a two-step method, and controllable preparation of CQDs to emit blue, green, yellow, and red fluorescence was achieved by adjusting the N-containing acid dopant. The investigated fluorescence mechanism revealed that the energy bandgap of the lignin-derived CQDs decreased and the emission wavelength redshifted as the graphitization degree and number of C=O surface groups increased. The light absorption region of the Bi7O9I3 photocatalysts modified with blue CQDs to red CQDs gradually broadened in the redshifted direction. In particular, compared with pure Bi7O9I3 (70.9%), the red CQDs-modified Bi7O9I3 (RCQD/BOI) can remove 94.7% of antibiotics within 60 min of light irradiation. The superior photocatalytic activity of RCQD/BOI is attributed to the established internal electric field that accelerates charge transfer and effectively separates the photogenerated e+-h+ inside Bi7O9I3. Furthermore, through radical capture, electron paramagnetic resonance (EPR) experiments validated the photocatalytic mechanism of RCQD/BOI and revealed that h+, O2− and OH are key reactants in the photocatalytic degradation process. This promising and sustainable approach for the synthesis of multicolor lignin-derived CQDs opens the avenue of high-value utilization of biomass resources, green production of CQDs nanomaterials, and efficient development of CQDs-based photocatalysts for wastewater treatment.

Probing charge transfer of NiCo2O4/g-C3N4 photocatalyst for hydrogen production

Quantum dots/two-dimensional (0D/2D) semiconductor photocatalysts demonstrate wide solar light absorption region and high charge transfer efficiency. However, the relation between the interfacial electric field and the charge transfer during the photocatalytic hydrogen production process is still unclear. Here, we construct NiCo2O4 quantum dots (QDs) and NiCo2O4 nanoparticles (NPs) anchored with 2D g-C3N4 (CN) to form NiCo2O4-QDs/CN and NiCo2O4-NPs/CN heterojunctions. The hydrogen production rate of CN loaded with NiCo2O4 QDs is about 3 times higher than that of CN loaded with NiCo2O4 NPs. The electric field intensity at the NiCo2O4-QDs/CN interface is calculated to be about 15,600 V cm−2, about 9 times higher than that of NiCo2O4-NPs/CN, which could effectively drive the electrons of CN to flow toward NiCo2O4 QDs, promoting photocarriers separation and hence greatly improving the photocatalytic performance. This work provides a method to understand the relationship between interfacial electric field strength and photogenerated charges of heterostructure photocatalysts.

Stable MOF-In2S3/ZnFe layered dioxide heterostructures for improving photocatalytic degradation: Degradation pathways, kinetics, and charge migration

In this paper, MOF-In2S3 were modified by ZnFe-layered dioxides (LDO) with strong stability to obtain high catalytic performance composite. The successful preparation of ZnFe-LDO/MOF-In2S3 not only retains the advantages of large specific surface area of MOF-In2S3 and the stability of ZnFe-LDO, but also improves its charge separation efficiency and the light absorption region through the construction of heterojunctions. As expected, the experimental results show that ZnFe-LDO/MOF-In2S3 has superior photo-electrocatalytic properties. The photocatalytic degradation efficiency of ZnFe-LDO/MOF-In2S3 for TCH and OTC reach 92.92% and 80%, respectively, within 25 min. And the corresponding degradation rate constants are up to 1.41332 and 0.45451 L·mg−1·min−1, respectively, which are accord with the pseudo-second-order kinetic constants. The intermediate of 0.6LDO/M-I degradation of TCH was proposed by liquid mass spectrometry (LC-MS). Notably, a special transient surface photovoltage (TPV) technique was used for discussing the charge transfer kinetics and the lifetime of photogenerated carriers. Based on Mott-Schottky (M-S), Ultraviolet-visible absorption spectrum (UV), X-ray Photoelectron Spectroscopy (XPS) results, electron paramagnetic resonance (EPR) results, and active substance capture experiment results, a Z-scheme heterojunction system was proposed. The above research work proposed a new approach to enhance the stability of catalytic materials by using the aid of layered dioxides. In addition, the characterization of surface photovoltage provides a new way to study charge transfer.

Synthesis of S-scheme 0D/2D Co2ZrO5/g-C3N4 heterojunction photocatalyst with enhanced visible-light photocatalytic activity for tetracycline

The step-like scheme (S-scheme) heterojunction photocatalyst, which possess an improved electric field, intimate interfacial contact and reasonable energy band structure, is one of the most optimal ways to solve the wastewater problem caused by residual antibiotics. Herein, a new type of S-scheme 0D/2D Co2ZrO5/g-C3N4 (CZO/CN) heterojunction photocatalyst was prepared via an ultrasonic assisted hydrothermal method and used as photocatalyst to degrade tetracycline (TC, 20 mg/L, 100 mL). Compared to pure CN and CZO, the CZO/CN with the optimal design proportion (30CZO/CN) demonstrates the outstanding photocatalytic efficiency for TC degradation under visible-light irradiation, with the degradation rate being 94.8 % within 180 min at pH 5.0. Moreover, the 30CZO/CN exhibits superior stability, which still eliminated 90 % of TC after five times cycle runs. Furthermore, the S-scheme mechanism of photocatalytic TC removal by CZO/CN is proposed by XRD, FT-IR, XPS, UV–Vis DRS and PL analysis, which summarized that the enhanced photocatalytic activity of CZO/CN was mainly ascribed to its larger specific surface area, available light absorption region and appropriate bandgap width, dominated by the S-scheme pattern. This study presents a novel S-scheme g-C3N4-base heterojunction photocatalyst can effectively treat wastewater and provides design ideas for other heterojunctions.

Novel 1,2,4-triazole sensitizers using N-arylsydnone as Synthon: Synthesis, Spectral, electrochemical, DFT and photovoltaic properties

Two novel 1,2,4-triazolone derivatized triphenylamine (TPA) and phenothiazine (PTZ) based metal-free organic dyes have been designed, synthesized and anchored on 1D CdS nanowires to serve as photoelectrochemical (PEC) dye-sensitized solar cells (DSSCs). Solution chemistry is employed simply and efficiently to link cadmium sulfide nanowires (CdS NWs) into a nano-network. Optical, electrochemical and density functional theory (DFT) have been well utilized to examine the properties of synthesized dyes (TPA and PTZ). In the visible range, sensitizer-anchored CdS NWs exhibit a wider region of light absorption referenced to naked CdS NWs. Comprehensive photovoltaic assessment showed that TPA and PTZ devices respectively showed IPCE 3.02 and 3.13 times more efficient than bare CdS NWs under standard sunlight (100 mW/cm2, AM 1.5G) illumination. The collected findings offer solid evidence for the existence of increasing external quantum efficiency (EQE) and exhibit good agreement with the optical experiments.

Ammonia induced strong LSPR effect of chain-like ATO nanocrystals for hyperspectral selective energy-saving window applications

Sb-doped SnO2 (ATO) is a promising multifunctional material with great potentials for practice applications, however, it suffers from poor absorption efficiency of near-infrared (NIR) light due to its relatively weak localized surface plasmon resonance (LSPR) effect. In this study, a series of chain-like ATO nanocrystals (NCs) with high Sb5+/Sb3+ ratio(s) and oxygen defect concentration were precisely prepared by a simple but efficient precipitation-hydrothermal method. The introduction of NH3 served as a double-hero in controlling both the solution pH and the shape of nanocrystals. Both experimental and theoretical calculation results have indicated that our synthesis strategy effectively increases the free carrier concentration and mobility of ATO NCs to improve LSPR effect, and thereby effectively broaden the NIR light absorption region and improve the absorption capacity. Furthermore, the as-prepared ATO hydrosols show great potentials for practical applications in energy-saving building since a flexible application mode as an energy-saving window can be implemented. Both the formation of ATO hydrosol windows by pouring into the laminated glass and spin-coating onto the flat glass to create ATO coatings can result in excellent optical properties and thermal insulation performance. These findings may not only accelerate the commercialization process of ATO but also provide valuable theoretical guidance for developing novel hyperspectral materials.

A novel multifunctional magnetically recyclable BiOBr/ZnFe2O4-GO S-scheme ternary heterojunction: Photothermal synergistic catalysis under Vis/NIR light and NIR-driven photothermal detection of tetracycline

The threat of tetracycline (TC) to human health has become a significant issue that cannot be disregarded. Herein, in order to achieve effective degradation and high-sensitivity detection of TC, BiOBr/ZnFe2O4-GO (BOB/ZFO-GO) S-scheme heterojunction nanocomposites (NCs) have been prepared using hydrothermal method. GO with high light absorption capacity accelerated the electron transfer between BiOBr and ZnFe2O4 nanocrystals and extended the light absorption region of BOB/ZFO NCs. The optimal GO addition of BOB/ZFO-GO NCs could degrade TC solution of 10 mg/L in 80 min and have a high reaction rate constant (k) of 0.072 min−1 under visible/NIR light. According to calculations, the non-metal photocatalyst (BOB/ZFO-GO(2)) with the best degradation performance had a photothermal conversion efficiency of up to 23%. Meanwhile, BOB/ZFO-GO NCs could be recycled by magnetic field. The excellent photocatalytic and photothermal performance could be maintained even after several cycles. In addition, a photothermal detection sensor based on a photothermal material/specific recognition element/tetracycline sandwich-type structure was constructed for the trace detection of TC concentration with a detection limit as low as 10-4 ng/mL. This research provides a unique idea for the multi-functionalization of photocatalysts and has a wide range of potential applications for the identification and treatment of organic wastewater.

Daul Z-scheme heterojunction BiOBr/Bi2O2.33/g-C3N4 for enhanced visible-light-driven tetracycline hydrochloride degradation

The construction of heterojunction photocatalysts with superior visible light photocatalytic performance is an effective strategy to addressing antibiotic pollution. A dual Z-scheme heterojunction BiOBr/Bi2O2.33/g-C3N4 was synthesized via hydrothermal and calcination methods, exhibiting exceptional degradation TC-HCL efficiency under visible light irradiation. The well-designed heterojunction was comprehensively supported by SEM, XPS, XRD and other series of characterization. Moreover, the BBCN50 heterojunction demonstrated an optimal degradation efficiency of 97.0% in 60 min compared to BB and CN with efficiencies of 90.8% and 70 respectively. The superior photocatalytic performance is attributed to the significantly broadened visible light absorption region and enhanced migration and separation of photogenerated electron-hole pairs facilitated by the fabricated heterojunction. Moreover, cyclic interpretation and free radical capture research have confirmed both the high stability of catalyst and its Z-type charge transfer mechanism.

2D/2D Ti3C2 MXene/HTiNbO5 nanosheets Schottky heterojunction for boosting photothermal-assisted solar-driven photodegradation of tetracycline hydrochloride

Developing high-efficiency photocatalysts for tetracycline hydrochloride (TCH) degradation is of great significance to ecosystems and human beings. In this work, a two-step process of exfoliation and re-stacking was performed to prepare re-stacked HTiNbO5 nanosheets (R-HTNS) and then coupled with Ti3C2 MXene to construct Ti3C2 MXene/R-HTNS (MX/RTS) with a 2D/2D Schottky heterojunction. These 2D/2D heterostructures between Ti3C2 MXene and R-HTNS can produce an internal electric field and provide maximum interface area for efficient charge transfer across the intimate interface. The photocatalytic performance of samples was evaluated by TCH degradation under simulated sunlight. The MX/RTS composites, with an optimal sample of 3-MX/RTS, show enhanced photocatalytic activity for TCH degradation compared with R-HTNS. The characterization results reveal that the introduction of Ti3C2 MXene can significantly increase specific surface area for providing more reactive sites and broaden the light absorption region. Besides, the incident light energy is absorbed by the Ti3C2 MXene component in MX/RTS composites to generate photothermal energy (heat), which facilitates the charge carrier separation and surface reaction kinetics. Thus, the enhanced TCH photodegradation activity for MX/RTS composites is due to the introduction of Ti3C2 MXene, which possesses the synergistic effect of the increased specific surface area, improved light-harvesting capacity, 2D/2D Schottky heterojunction, and photothermal energy effect. Additionally, the TCH photodegradation behavior is deliberated with a detailed discussion on various coexisting ions. During TCH photodegradation, the active radical species are determined for 3-MX/RTS. According to the characterization results, the possible TCH photodegradation pathway and mechanism over 3-MX/RTS are explored. This work may offer a novel insight for constructing MXene-based heterostructured photocatalysts with high efficiency.

Boosting the sonophotocatalytic performance of BiOCl by Eu doping: DFT and an experimental study

Bismuth oxychloride (BiOCl) has a unique layered structure and uneven charge distribution, resulting in an internal electric field under polarization, which promotes the efficient separation and migration of photogenerated carriers. BiOCl could be a candidate for sonophotocatalysts. However, the low utilization of visible light limits the application of BiOCl in photocatalysts. In this study, the photocatalytic performance of rare earth element (Nd, Sm, Eu, Er and Er)-doped BiOCl was studied by density functional theory (DFT) and experimentally to screen high-performance catalysts. The band structure, density of states, and optical properties were calculated by the DFT method to predict the photocatalytic activity of rare earth-doped BiOCl. The built-in electric field formed in Eu-doped BiOCl inhibiting electron and hole recombination can be observed. Subsequently, the activity of the photocatalyst and sonophotocatalysts was evaluated. The results show that the photocatalytic and sonophotocatalytic activity of Eu-doped BiOCl is improved, which is consistent with the theoretical prediction. Combining theoretical calculations with experiments, the sonophotocatalytic activity of Eu-doped BiOCl is enhanced, mainly due to the synergistic effect of inhibiting carrier recombination, and expansion to the visible light absorption region.

Effect of bandgap variation on photovoltaic properties of lead sulfide quantum dot solar cell

The tunable bandgap of quantum dot (QD)-based solar cells is their greatest advantage, providing control over light absorption region. However, the investigation of the effect of bandgap variation on QD-based photovoltaic properties is insufficient, in contrast to well-defined material properties. In this study, we analyze the electrical properties of solar cells fabricated with bandgap-tuned lead sulfide (PbS) QDs to examine the effect of bandgap variation on photovoltaic properties. We find that reducing the thickness of the QD active layer is necessary to achieve high power conversion efficiency mainly because the doping concentration of the QD film increases as the QD bandgap decreases. We suggest that QD photovoltaic device structures should be designed with consideration of their electrical characteristics in relation to the bandgap.

Replacing CC Unit with B←N Unit in Isoelectronic Conjugated Polymers for Enhanced Photocatalytic Hydrogen Evolution.

Three linear isoelectronic conjugated polymers PCC, PBC, and PBN are synthesized by Suzuki-Miyaura polycondensation for photocatalytic hydrogen (H2 )production from water. PBN presented an excellent photocatalytic hydrogen evolution rate (HER) of 223.5µmolh-1 (AQY420 =23.3%) under visible light irradiation, which is 7 times that of PBC and 31 times that of PCC. The enhanced photocatalytic activity of PBN is due to the improved charge separation and transport of photo-induced electrons/holes originating from the lower exciton binding energy (Eb ), longer fluorescence lifetime, and stronger built-in electric field, caused by the introduction of the polar B←N unit into the polymer backbone. Moreover, the extension of the visible light absorption region and the enhancement of surface catalytic ability further increase the activity of PBN. This work reveals the potential of B←N fused structures as building blocks as well as proposes a rational design strategy for achieving high photocatalytic performance.

Li2MnO3 nanoparticles decorated with Co3O4 as functional visible-light-induced heterojunction photocatalysts for the degradation of tetracycline

Fabrication of heterojunction nanocomposites as effective photocatalysts with high photocatalytic ability is critical to secure our environment's safety. Herein, a novel approach to creating a stable and effective heterojunction of Li2MnO3/Co3O4 photocatalyst is presented. TEM and XRD analyses indicate that the high crystallinity phase of monoclinic Li2MnO3 and cubic Co3O4 was formed with a uniform shape (10–15 nm). The obtained Li2MnO3/Co3O4 photocatalysts were utilized for the photocatalytic degradation of tetracycline (TC) under visible light. The 12% Li2MnO3/Co3O4 sample achieved a maximal photocatalytic performance of 100% after 105 min, which was two times greater than that of pure Co3O4, and its rate constant was improved to 2.1 times that of Co3O4. The photocatalytic mechanism was verified utilizing the time-resolved photoluminescence (TRPL) spectra, photocurrent density, photoluminescence (PL) spectra, EIS Nyquist plots and Mott-Schottky curves. The enhanced photocatalytic performance of the Li2MnO3/Co3O4 nanocomposites is attributed to the construction of heterojunctions with a synergistic effect, which obstruct electron-hole recombination, extend the light absorption region, and accelerate the separation of carriers. The obtained heterojunction Li2MnO3/Co3O4 photocatalyst was effective and stable after five cycling runs under visible illumination. As a result, this effective, facile, and green strategy provides a new horizon to recognize mesoporous Co3O4-based photocatalysts for photocatalysis applications under visible illumination.

Fabrication of Bi2O3 QDs decorated TiO2/BiOBr dual Z-scheme photocatalysts for efficient degradation of gaseous toluene under visible-light

Weak visible-light capture ability, ultrahigh charge recombination rate, and poor redox ability are crucial constraints to improve the photocatalytic performance for toluene degradation under visible-light. Hence, a dual Z-scheme of Bi2O3 quantum dots decorated TiO2/BiOBr photocatalysts (Bi2O3 QDs@TiO2/BiOBr) were prepared by a two-step hydrothermal method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were performed to identify the existence of Bi2O3 QDs and TiO2 that loaded on the surface of BiOBr. The introducing of oxygen vacancies in TiO2 broadened its light absorption region to the visible-light. The constitutes of Bi2O3 QDs and BiOBr were regulated and the optimized photocatalyst BT1-B10 exhibited 94.1 % of removal rate for gaseous toluene degradation after 150 min irradiation of visible-light (>420 nm) as well as good recoverability and durability. This result was obviously superior to other comparison samples. In-situ DRIFTs spectra and Gas Chromatography-Mass Spectrometry (GC-MS) were carried out to provide a possible pathway for the toluene degradation. Additionally, a dual-channel electron transfer model based on the Z-scheme was proposed, which presented desirable visible-light response region, efficient charge separation efficiency, and enhanced redox ability. Notably, hydroxyl radicals (•OH) served as the dominant active species was confirmed by electron spin resonance (ESR) and gas-phase capture tests, that was beneficial to the ring-opening of toluene degradation. This dual Z-scheme heterojunction of Bi2O3 QDs@TiO2/BiOBr photocatalyst showed great potential for the degradation of toluene under visible-light irradiation.