Natural Sunlight Irradiation Research Articles

3-D/3-D Z-Scheme Heterojunction Composite Formed by Marimo-like Bi2WO6 and Mammillaria-like ZnO for Expeditious Sunlight Photodegradation of Dimethyl Phthalate

In the present work, we assessed the photocatalytic performance of the new 3-D/3-D Z-scheme heterojunction composite for the degradation of dimethyl phthalate (DMP). The composite was composed by marimo-like Bi2WO6 and mammillaria-like ZnO which was named BWZ. The composite was successfully fabricated using a hydrothermal-precipitation method and analyzed via different characterization techniques. Under natural sunlight irradiation, the optimal composite with 20 wt% of Bi2WO6/ZnO (20-BWZ) exhibited a photodegradation rate constant of 0.0259 min−1, which reached 2.3 and 5.9-folds greater than those of pure ZnO (0.0112 min−1) and Bi2WO6 (0.0044 min−1), respectively. That was predominantly attributed to the formation of a Z-scheme photocatalytic system in the as-synthesized composite reduced the charge carrier recombination and accelerated the photoactivity. Transient photocurrent response and electrochemical impedance spectroscopy analyses were performed to confirm this conclusion. The reusability test indicated that the 20-BWZ had no significant deactivation after four runs, which inferred good stability of the as-prepared composite. Furthermore, the quenching test demonstrated that the photogenerated hole, superoxide anion radical and hydroxyl radical were all involved in the photodegradation of DMP, among which •OH was the principal reactive species. This work revealed that the as-prepared BWZ composites have great potential applications for the degradation of refractory pollutants in the environmental remediation field.

Thiadiazole-Based Covalent Organic Frameworks with a Donor-Acceptor Structure: Modulating Intermolecular Charge Transfer for Efficient Photocatalytic Degradation of Typical Emerging Contaminants.

As novel metal-free photocatalysts, covalent organic frameworks (COFs) have great potential to decontaminate pollutants in water. Fast charge recombination in COFs yet inhibits their photocatalytic performance. We found that the intramolecular charge transfer within COFs could be modulated via constructing a donor-acceptor (D-A) structure, leading to the improved photocatalytic performance of COFs toward pollutant degradation. By integrating electron donor units (1,3,4-thiadiazole or 1,2,4-thiadiazole ring) and electron acceptor units (quinone), two COFs (COF-TD1 and COF-TD2) with robust D-A characteristics were fabricated as visible-light-driven photocatalysts to decontaminate paracetamol. With the readily excited electrons in 1,3,4-thiadiazole rings, COF-TD1 exhibited efficient electron-hole separation through a push-pull electronic effect, resulting in superior paracetamol photodegradation performance (>98% degradation in 60 min) than COF-TD2 (∼60% degradation within 120 min). COF-TD1 could efficiently photodegrade paracetamol in complicated water matrices even in river water, lake water, and sewage wastewater. Diclofenac, bisphenol A, naproxen, and tetracycline hydrochloride were also effectively degraded by COF-TD1. Efficient photodegradation of paracetamol in a scaled-up reactor could be achieved either by COF-TD1 in a powder form or that immobilized onto a glass slide (to further ease recovery and reuse) under natural sunlight irradiation. Overall, this study provided an effective strategy for designing excellent COF-based photocatalysts to degrade emerging contaminants.

Photocatalytic degradation of ciprofloxacin antibiotic in water by biosynthesized silica supported silver nanoparticles

This study reports photocatalytic degradation of ciprofloxacin (CIP) in the presence of silver nanoparticles impregnated over amorphous silica extracted from rice husk through a green approach using Melia Azedarach fruit extract. Various analyses such as X-ray diffraction analysis (XRD), Fourier-transform infrared (FTIR) spectroscopy, and field emission scanning electron microscopy (FESEM) were employed to characterize the obtained nanocomposite. Afterward, the photocatalytic activity of the nanocomposite was studied in the removal of CIP from an aqueous solution under natural sunlight irradiation. Moreover, the effect of various parameters such as solution initial pH (3–11), reaction time (30–180min), and catalyst loading (0.03–0.12 g) on degradation efficiency were studied by applying a design of experiment (DOE) methodology. The results indicated the successful synthesis and deposition of Ag nanoparticles over amorphous silica. The results of degradation experiment confirmed the acceptable performance of Ag/silica nanocomposite in photo-degradation of CIP. According to the experimental design, both catalyst loading and reaction time are highly significant; whereas the initial pH is not significant compared to other factors. Moreover, the optimal conditions were determined to be initial pH = 6.7, reaction time = 180 min, and catalyst loading of 0.12 g. By applying these optimal conditions, degradation efficiency reached to 98%. Moreover, the results of kinetic study revealed that the photo-degradation of CIP in presence of Ag/silica nanocomposite obeys a first-order kinetic model. The Ag/silica nanocomposite exhibited a high level of stability as the nanocomposites could preserve their stability after three sequential degradation cycles.

Architectural MCM 41 was anchored to the Schiff base Co(II) complex to enhance methylene blue dye degradation and mimic activity

A sequence of Schiff base Cobalt (II) Mobile Composite Matter 41 heterojunction (SBCo(II)-MCM 41) was prepared by post-synthetic protocols. Various characterization techniques were used to characterize the above samples and MCM 41: Morphology, functional groups, optical properties, crystalline nature, pore diameter, and binding energy by scanning electron microscope (SEM), High-resolution transition electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), Ultra Violet-Visible Spectroscopy (UV), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) and X-ray Photoelectron Spectroscopy (XPS). After the encapsulation of SBCo(II) on the MCM 41, the intensity in the 100-plane in powder x-ray diffraction (XRD) decreased significantly; moreover, the light absorption behavior in UV analysis was improved. The change in the surface area and the decrease in the pore diameter of the sample were also demonstrated by the BET study. The XPS results confirmed the presence of Si, O, C, N, and Co in the SBCo(II)-MCM 41 complex. The photocatalytic performance of MCM 41 and SBCo(II)-MCM 41 materials tested by the degradation of methylene blue dye (MBD) shows that MCM 41 immobilization with SBCo(II)complex is rapidly degraded under natural sunlight irradiation. The optimized 10 mg SBCo(II)-MCM 41 catalyst concentrations showed effective enhancement with the highest efficiency of 98% achieved within 2 h compared to the other two SBCo(II)-MCM 41 concentrations. Moreover, the catalytic efficiency of SBCo(II)-MCM 41 showed a biomimetic reaction without using an oxidant, which exposed it as an effective catalyst for amine to imine conversion; it was useful in the medical field for enzymes with structural assembly.

Three-Dimensional Hierarchical Seaweed-Derived Carbonaceous Network with Designed g-C3N4 Nanosheets: Preparation and Mechanism Insight for 4-Nitrophenol Photoreduction.

The development of g-C3N4-based photocatalysts with abundant active sites is of great significance for photocatalytic reactions. Herein, a smart and robust strategy was presented to fabricate three-dimensional (3D) g-C3N4 nanosheet-coated alginate-based hierarchical porous carbon (g-C3N4@HPC), including coating melamine on calcium alginate (CA) hydrogel beads, freeze-drying hydrogel beads as well as pyrolysis at high temperatures. The resulting photocatalyst possessed a significantly high surface area and a large amount of interconnected macropores compared with porous carbon without the melamine coating. The unique structural features could effectively inhibit the curling and agglomeration of g-C3N4 nanosheets, provide abundant photocatalytic active sites, and promote mass diffusion. Therefore, the g-C3N4@HPC composite exhibited remarkable photocatalytic activity and outstanding stability toward the photoreduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 under natural sunlight and simulated visible-light irradiation (λ > 420 nm) using a 300 W xenon lamp. Moreover, the mechanism toward the photocatalytic reaction was extensively studied by quenching experiments and electron spin resonance (ESR) experiments. The results showed that active hydrogen species were able to be achieved by following a dual-channel pathway in the NaBH4 system, which included photocatalytic reduction of H+ ions and photocatalytic oxidation of BH4- ions. This work not only opens up a new way to design efficient photocatalysts for various reactions but also provides a reference for an in-depth study of the photoreduction mechanism.

CuWO4 as a novel Z-scheme partner to construct TiO2 based stable and efficient heterojunction for photocatalytic hydrogen generation

Synthesis of highly efficient, stable, visible active CuWO4 nanoparticles through a simple methodology, paves a feasible path for enhancing the efficiency of TiO2. A novel nanocomposite of CuWO4 NP loaded TiO2 NR heterojunction was mounted through a direct Z-scheme mechanism. Optimized composite CWT-3, advances the photocatalytic hydrogen production rates of TiO2 to 106.7 mmol h−1 g−1cat. CuWO4 incorporation as OEP compensates inefficiency of WO3 and other Z-scheme combinations reported so far, on limiting the charge carrier recombination followed by the generation of a greater number of excitons. Specific amounts of catalyst loading, study on the effect of sacrificial reagents, and understanding the effect of the light source, are the three pivotal steps that helped here to hamper the density of overall back reactions. The formation of Z-scheme heterojunction was evidently confirmed on determining the position of CBM and VBM, PL and photoelectrochemical analysis. Recyclability studies further proved the stable and efficient outcomes of CWT-3 for five consecutive cycles. Based on photocatalytic activity, employing BDF by-product glycerol as an optimized sacrificial reagent serves the oxidation demands and triggered 53.26% solar to hydrogen conversion efficiency under natural sunlight irradiation.

Sunlight-activated periodate oxidation: A novel and versatile strategy for highly efficient water decontamination

This study reported for the first time that the sunlight-activated periodate (PI) system could appreciably boost the selective abatement efficiency of emerging organic contaminants from the aqueous environment. The sunlight/PI system completely removed bisphenol F after 30 min, which was slightly affected by multiple coexisting water constituents, suggesting its selective oxidation characteristics. This combined system could also eliminate other micropollutants under simulated or natural sunlight irradiation. Multiple lines of evidence demonstrated the production of different oxidizing intermediates such as singlet oxygen (1O2), hydroxyl radicals, and superoxide radicals. Among these species, 1O2 was convincingly deemed as the predominant oxidizing species contributing to the exceptional elimination of different micropollutants. Additionally, PI was stoichiometrically transformed into the unharmful iodate ion without forming other iodine species. Product analysis of three model pharmaceuticals (methotrexate, propranolol, and sitagliptin) signified that the proposed oxidation system could introduce the degradation products of plausibly enhanced biodegradability. Notably, 30 min of sunlight/PI treatment could also efficiently eliminate micropollutants from the highly saline water and accomplish prominent water disinfection. Overall, the major contribution of this investigation is to provide a novel, highly efficient, selective, green, and versatile oxidation strategy for sustainable water purification using the chemical-free natural activator.

Engineering high-emissive silicon-doped carbon nanodots towards efficient large-area luminescent solar concentrators

Luminescent solar concentrators (LSCs) are devices that can collect sunlight from a large area, concentrating it at the borders of the slab, to achieve efficient photovoltaic conversion when small area solar cells are placed at their edges, realizing building-integrated photovoltaics. Efficient luminophores in terms of high luminescence quantum yield are needed to obtain high-performance LSCs. A key point is the ability to engineer the Stokes shift (i.e. the difference between the maximum of the absorption and emission spectra), to minimize reabsorption processes. In this work, we report novel silicon-doped carbon nanodots (Si-CDs) with an ultrahigh quantum yield (QY) up to 92.3% by a simple hydrothermal method. Thin-film structured LSCs (5 × 5 × 0.2 cm3) with different concentrations of Si-CDs are prepared by dispersing the Si-CDs into polyvinyl pyrrolidone (PVP) matrix, and the optimal power conversion efficiency (PCE) of LSCs can be as high as 4.36%, which is nearly 2.5 times higher than that prepared with silicon-undoped CDs. This Si-CDs/PVP film LSC has a high QY of 80.5%. A large-area LSC (15 × 15 cm2) is also successfully fabricated, which possesses a PCE of 2.06% under natural sunlight irradiation (35 mW·cm−2), one of the best reported values for similar size LSCs. The efficient Si-CDs as luminescent substances for high-efficiency large-area LSCs will further give an impetus to the practical exploitation of LSCs.

(Invited) Solar Hydrogen Production with Particulate Photocatalysts

Sunlight-driven water splitting is studied actively for production of renewable solar hydrogen on a large scale. Both the efficiency and scalability of water splitting systems are essential factors for practical application of renewable solar hydrogen because of the low areal density of the solar energy. In this context, overall water splitting using particulate photocatalysts has been attracting growing interest, because such systems can be spread over wide areas by inexpensive processes potentially [1], although it is essential to radically improve the solar-to-hydrogen energy conversion efficiency (STH) of particulate photocatalysts and develop suitable reaction systems. In my talk, recent progress in photocatalytic materials and reaction systems will be presented.The author’s group has studied various semiconductor oxides, (oxy)nitrides, and (oxy)chalcogenides as photocatalysts for water splitting [2]. SrTiO3 is an oxide photocatalyst that has been known to be active in overall water splitting under ultraviolet irradiation since 1980 [3]. Recently, the apparent quantum yield (AQY) of this photocatalyst in overall water splitting has been improved drastically. The author's group has found that doping Al3+ into the titanium site of SrTiO3 boosts the water splitting activity by two orders of magnitude [4]. By refining the preparation conditions of the Al-doped SrTiO3 (SrTiO3:Al) photocatalyst and the loading conditions of cocatalysts working as hydrogen and oxygen evolution sites, the AQY has been improved to more than 90% at 365 nm [5], equivalent to an internal quantum efficiency of almost unity. This quantum efficiency is the highest yet reported and indicate that a particulate photocatalyst can drive the greatly endergonic overall water splitting reaction at a quantum efficiency comparable to values obtained from photon-to-chemical or photon-to-current conversion in photosynthesis or photovoltaic systems, respectively.The author's group has also been developing panel reactors for large-scale applications. Photocatalyst sheets based on SrTiO3:Al contained in a panel-type reactor split water into hydrogen and oxygen and release gas bubbles at a rate corresponding to a solar-to-hydrogen energy conversion efficiency of 10% under intense ultraviolet irradiation even when the water depth is merely 1 mm [6]. Moreover, the photocatalyst can maintain 80% of its initial activity during 1300 h of constant simulated sunlight irradiation at ambient pressure with appropriate surface modifications [7]. A prototype 1-m2-sized panel reactor containing SrTiO3:Al photocatalyst sheets splits water under natural sunlight irradiation without a significant loss of the intrinsic activity of the photocatalyst sheets. More recently, a solar hydrogen production system based on 100-m2 arrayed photocatalytic water splitting panels and an oxyhydrogen gas-separation module was built, and its performance and system characteristics including safety issues was reported [8].For practical solar energy harvesting, it is essential to develop photocatalysts that are active under visible light irradiation. Ta3N5 and Y2Ti2O5S2 photocatalysts are active in overall water splitting via one-step excitation under visible light irradiation [9,10]. Particulate photocatalyst sheets efficiently split water into hydrogen and oxygen via two-step excitation, referred to as Z-scheme, regardless of size. In particular, a photocatalyst sheet consisting of La- and Rh-codoped SrTiO3 and Mo-doped BiVO4 splits water into hydrogen and oxygen via the Z-scheme, showing a STH exceeding 1.0% [11,12]. Some other (oxy)chalcogenides and (oxy)nitrides with long absorption edge wavelengths can also be applied to Z-scheme photocatalyst sheets. Hisatomi et al., Nat. Catal. 2019, 2, 387.Chen et al., Nat. Rev. Mater. 2017, 1, 17050.Domen et al., J. Chem. Soc., Chem. Commun. 1980, 543Ham et al., J. Mater. Chem. A 2016, 4, 3027.Takata et al., Nature 2020, 581, 411.Goto et al., Joule 2018, 2, 509.Lyu et al., Chem. Sci. 2019, 10, 3196.Nishiyama et al., Nature 2021, 598, 304.Wang et al., Nat. Catal. 2018, 1, 756.Wang et al., Nat. Mater. 2019, 18, 827.Wang et al., Nat. Mater. 2016, 15, 611.Wang et al., J. Am. Chem. Soc. 2017, 139, 1675.

The impact of natural sunlight irradiation on the biotoxicities of different molecular sizes EfOM/SRNOM and its relationship with spectral and molecular level parameters

Natural sunlight irradiation is regarded as an efficient and low-carbon method for controlling the biotoxicity of effluents from domestic wastewater treatment plants (WWTPs). Dissolved organic matter in WWTPs effluent (EfOM) is responsible for the non-specific biotoxicity of effluent. In the present study, the variation in spectral characteristics, molecular composition, luminescent bacteria toxicity, and genotoxicity of EfOM of different molecular sizes (MOSs) during natural sunlight irradiation were investigated from a systematic perspective, and the standard natural organic matter from the Suwannee River (SRNOM) was synchronously assessed for comparative purposes. To further explore the cause of the biotoxicity changes, the relationships between the spectral or molecular level parameters (obtained from FT-ICR MS analysis) and biotoxicity were assessed using correlation analysis. The molecules in <1 kDa EfOM with lower molecular weight, higher unsaturation degree, and higher humification and fluorescence had higher luminescent bacteria toxicity under sunlight irradiation. However, in the <1 kDa SRNOM, the molecules which were characterized by higher humification and fluorescence had higher luminescent bacteria toxicity. The notable genotoxicity reduction of EfOM under sunlight irradiation was attributed to the photochemical degradation of components with a high unsaturation degree. Such findings could enable ecological safety improvement of aquatic environments using natural sunlight.

A super absorbent resin-based solar evaporator for high-efficient various water treatment

Currently, water treatment has been viewed as an important way to the growing shortage of fresh water. A solar vapor generation device demonstrated enormous potential for desalination, water purification and carbon emission reduction. Nevertheless, the high cost and scalability hurdles of solar evaporators fundamentally restrict the practicality of solar-driven water treatment. In this study, an industrialized sodium polyacrylate (PAANa) super absorbent resin together with commercial carbon nanotubes (CNTs) is used to construct a PAANa-based solar evaporator. Under synergistic effects of high photothermal conversion efficiency, larger actual evaporation area, and reasonable water distribution on the evaporation surface, PAANa-based solar evaporator achieves a high water evaporation rate of 7.47 kg m−2 h−1 under 1 sun illumination (1 kW m−2) and convective flow condition. Notably, many kinds of sewage including dye-containing sewage, seawater, oil-in-water emulsion, and real industrial sewage can be effectively purified by using PAANa-based solar evaporator. Moreover, in arid and water-deficient areas, the PAANa-based evaporator with a strong water extraction capacity can easily capture water from gravel crevices and simultaneously purify it for further use. Significantly, under natural sunlight irradiation, a large-area PAANa-based evaporator (about 415 cm2) provided a sewage treatment capacity of up to 11.93 kg m− 2 for a continuous 10 h. This study will offer a new possibility for the industrialization of cost-effective and scalable solar evaporators, which can be used to alleviate the global water resources shortages.

Green synthesis of nickel oxide coupled copper hexacyanoferrate (NiO2–CuHCF) nanocomposites for efficient and highly stable natural sunlight-driven photocatalytic degradation of wastewater pollutants

Metal hexacyanoferrates are found to be the promising candidates utilized to degrade toxic dyes from waste water under natural sunlight irradiation. Coupling of metal hexacyanoferrate with metal oxide enhances the degradation efficacy. In present work, nickel oxide coupled copper hexacyanoferrate nanocomposites (NiO2–CuHCF) are synthesized by employing facile co-precipitation route. XRD reveals the incorporation of NiO2 with CuHCF. SEM confirms the sheet like structures of NiO2–CuHCF nanocomposite. TEM demonstrates the even distribution of elements present in the NiO2–CuHCF nanocomposite. XPS shows the active participation of constituents having different valence states. The UV–Vis (DRS) is employed to measure the optical properties. The band gap of nickel oxide coupled copper hexacyanoferrate nanocomposite (NiO2–CuHCF) decreases in comparison with pure copper hexacyanoferrate (CuHCF) from 1.23 to 1.14 eV. 97% degradation of Methyl blue (MB) is observed in just 110 min by NiO2–CuHCF nanocomposite when exposed to natural sunlight. Moreover, it also retains 92% photocatalytic efficiency over 6 cycles which shows its excellent stability and reusability. The improved photocatalytic performance of NiO2–CuHCF nanocomposite is attributed to their sheet resembling morphologies which may provide adequate active sites responsible to transport more charge carriers and also reduce charge recombination. In general, this research may open new avenue to use CuHCF with the addition of NiO2 in future as an efficient degradation agent at industrial level.

Synthesis and characterization of Se-doped ZnO nanocomposit material and its multi applications

The novel Se-doped ZnO nancomposite material was prepared using the sol-gel technique. The nanocomposite material at 250, 500, and 600 degrees Celsius at M.F 3 h respectively in material has been studied toward the removal of Methyl Green (MG) dye by UV and natural sun-light irradiation as a model organic pollutant from the textile industry and its stability and reusability. SEM and TEM analysis reveal the nano-flakes and nano-spherical structure. Low intensity and low band gap energy with high photocatalytic and electrochemical activity are reported by PL and DRS. We also talked about dye-sensitized solar cell applications based on vegetables (natural dye) that were reported.

Natural light driven photovoltaic-electrolysis water splitting with 12.7% solar-to-hydrogen conversion efficiency using a two-electrode system grown with metal foam

Currently, photovoltaic-electrocatalytic (PV-EC) water splitting possesses the paramount solar-to-hydrogen energy conversion efficiency (STH) among various solar energy conversion and storage systems. However, three principal factors including noble metal-based electrodes, expensive photovoltaic cell, and concentrated solar light systems largely limited the large-scale practicable implementation of this strategy. In this work, CoNi layered-double-hydroxide (LDH) nanosheets arrays, CoFe2O4 nanoparticles and CoNi LDH/CoFe2O4 composite electrodes are controllably synthesized on Ni foam, Fe foam and NiFe alloy foam, respectively, via a facile hydrothermal process. Experiments and density-functional theory calculation results demonstrate that CoFe2O4 and CoFe2O4/CoNi LDH electrodes are suitable to be used as highly efficient, stable, and freestanding water-splitting electro anode and cathode, respectively. Significantly, combining with a commercial silicon-based solar cell, the assembled PV-EC water splitting device receives 12.7% STH under natural sunlight irradiation. This work provides a typical demonstration and valuable guidelines for practical large-scale solar-to-hydrogen generation using an inexpensive PV-EC technology.

Catalyst-Free Periodate Activation by Solar Irradiation for Bacterial Disinfection: Performance and Mechanisms.

Periodate (PI)-based advanced oxidation process has recently attracted great attention in the water treatment processes. In this study, solar irradiation was used for PI activation to disinfect waterborne bacteria. The PI/solar irradiation system could inactivate Escherichia coli below the limit of detection (LOD, 10 CFU mL-1) with initial concentrations of 1 × 106, 1 × 107, and 1 × 108 CFU mL-1 within 20, 40, and 100 min, respectively. •O2- and •OH radicals contributed to the bacterial disinfection. These reactive radicals could attack and penetrate the cell membrane, thereby increasing the amount of intracellular reactive oxygen species and destroying the intracellular defense system. The damage of the cell membrane caused the leakage of intracellular K+ and DNA (that could be eventually degraded). Excellent bacterial disinfection performance in PI/solar irradiation systems was achieved in a wide range of solution pH (3-9), with coexisting humic acid (0.1-10 mg L-1) and broad solution ionic strengths (15-600 mM). The PI/solar irradiation system could also efficiently inactivate Gram-positive Bacillus subtilis. Moreover, PI activated by natural sunlight irradiation could inactivate 1 × 107 CFU mL-1 viable E. coli below the LOD in the river and sea waters with a working volume of 1 L in 40 and 50 min, respectively. Clearly, the PI/solar system could be potentially applied to disinfect bacteria in water.

The environmental fate of biomass associated polybrominated diphenyl ethers

The widespread use of polybrominated diphenyl ethers (PBDEs) inevitably leads to their occurrence in the atmosphere, soil, and sediment. Biomass, especially dry branches and fallen leaves, may act a large reservoir for PBDEs through atmospheric deposition or soil bioaccumulation. Thus, clarifying the sunlight-induced transformation behaviors of PBDEs on biomass is highly significant for our understanding on its natural self-purification process. In this work, the degradation kinetics and mechanisms of two common PBDEs congeners, decabromodiphenyl ether (BDE-209) and 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47), on biomass were systematically studied under natural and simulated sunlight irradiation conditions. The highest photodegradation rate constant of BDE-209 and BDE-47 was observed on sour cherry (SC) and zoysia matrella (ZM), respectively, which was related to their larger light receiving area and poor crystallinity. Due to the higher apparent quantum efficiency, BDE-209 degrades faster than BDE-47 (0.063–0.223 vs 0.006–0.026 h−1). The sunlight self-purification cycle of BDE-209 and BDE-47 on biomass were 6 and 14 days, respectively, with the corresponding sunlight contribution in the range of 0.12–0.51 ng mW−1. Products analysis by GC-MS and HPLC-MS/MS revealed that the main reactions involved in the photodegradation of BDE-209 and BDE-47 on biomass were debromination, hydroxylation, cyclization, and C–O bond breaking reaction. Especially, it was firstly proposed that hydroxyl H in lignin from biomass participated in the formation of primary products, which were rationalized by density functional theory (DFT) calculations and control experiments.

UVA Light‐promoted Catalyst‐free Cyclization of Vinyl Selenides: Green and Efficient Synthesis of C3‐Unsubstituted 2‐Selanyl Benzochalcogenophenes

A metal- and catalyst-free photo-promoted cyclization of properly substituted vinyl selenides was developed using UVA irradiation. A total of eighteen new C3-unsubstituted 2-selanyl benzochalcogenophenes (benzofurans, benzothiophenes and benzoselenophenes) were prepared in 30-86% yield after irradiation with UVA at room temperature. The usefulness of the title compounds was demonstrated in the easy functionalization of the remaining free C-H bond of the benzochalcogenophenes to form new C-Se and C-Br bonds by simple procedures. Furthermore, the reaction can be performed under natural sunlight irradiation and the solvent is easily reused further in several subsequent runs.

Natural Sunlight Driven Photocatalytic Removal of Toxic Textile Dyes in Water Using B-Doped ZnO/TiO2 Nanocomposites

A novel B-doped ZnO/TiO2 (B–ZnO/TiO2) nanocomposite photocatalyst was prepared using a mechanochemical–calcination method. For the characterization of the synthesized B–ZnO/TiO2 photocatalyst, XRD, FESEM-EDS, FTIR, UV-Vis DRS, BET, PL, and XPS techniques were used. The bandgap energy of B–ZnO/TiO2 was reduced, resulting in enhanced visible-light absorption. Significant PL quenching confirmed the reduction in the electron–hole recombination rate. Furthermore, reduced crystallite size and a larger surface area were obtained. Hence, the B–ZnO/TiO2 photocatalyst exhibited better photocatalytic activity than commercial TiO2, ZnO, B–ZnO, and ZnO/TiO2 in the removal of methylene blue (MB) dye under natural sunlight irradiation. The effects of various parameters, such as initial concentration, photocatalyst amount, solution pH, and irradiation time, were studied. Under optimal conditions (MB concentration of 15 mg/L, pH 11, B–ZnO/TiO2 amount of 30 mg, and 15 min of operation), a maximum MB removal efficiency of ~95% was obtained. A plausible photocatalytic degradation mechanism of MB with B–ZnO/TiO2 was estimated from the scavenger test, and it was observed that the •O2− and •OH radicals were potential active species for the MB degradation. Cyclic experiments indicated the high stability and reusability of B–ZnO/TiO2, which confirmed that it can be an economical and environmentally friendly photocatalyst.

The synthesis of a novel conjugated microporous polymer and application on photocatalytic removal of uranium(Ⅵ) from wastewater under visible light

• A novel porphyrin-based CMP(TT-TPP) showed wide visible light adsorption. • The U(Ⅵ) removal capacity of TT-TPP was 3571.2 mg g −1 . • 80% uranium removal was achieved under solar irradiation. • Good removal rates were reached on high acidity and high salt condition. • TT-TPP displayed a fine selectivity for U(Ⅵ) from simulated radioactive wastewater. Photocatalytic reduction of uranium(Ⅵ) is an efficient and non-pollutant strategy for removal of uranium(Ⅵ) from waste water. However, most current photocatalysts are limited in practical application due to low visible light utilization and low activity on acidic condition. In this work, a new conjugated microporous polymer (CMP) named TT-TPP has been synthesized by C–H arylation between 5, 10, 15, 20-tetrakis(4-bromophenyl)-porphyrin and thieno[3,2-b]thiophene. TT-TPP exhibits excellent chemical stability and photochemical property. It can be used for visible light driven photocatalytic reduction of U(VI) on highly acidic condition (pH = 2–5) with high uranium removal capacity (3571.2 mg g −1 ). Even in 3 M NaNO 3 solution, the removal rate of U(Ⅳ) could reach to 89.9%. TT-TPP still exhibits an excellent uranium selectivity over these competing metal cations, and 97.6% U(Ⅳ) in simulated radioactive wastewater is removed. The X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and the fourier transform infrared spectroscopy (FT-IR) confirmed the reduced uranium was in the form of UO 2 ⋅nH 2 O. In addition, TT-TPP also shows excellent photocatalytic U(VI) reduction performance under natural sunlight irradiation.

Highly-efficient photocatalytic activity of TiO2-AC nanocomposites for hydrogen production from sulphide wastewater

Photocatalytic water splitting is one of the prospective green energy technologies, particularly, for hydrogen production from wastewater under natural sunlight irradiation. Herein, we report experimental data on the synthesis and characteristics of the biomass activated carbon (b-AC)-anchored anatase titanium oxide (a-TiO2) nanocomposites, which were ultrasonically prepared by using the sol-gel-grown a-TiO2 spherical nanoparticles and the KOH-activated citron-derived b-AC nanoflakes. The a-TiO2/b-AC nanocomposites displayed an aggregated morphology with the interconnected spherical nanoparticles, and they showed a high surface area (495 m2/g). When using a-TiO2/b-AC as a photocatalyst for hydrogen production from sulphide wastewater (0.15 M) under solar irradiation (740 W/m2), the superb hydrogen production efficiency was achieved up to 400 mL/h. The results suggest the a-TiO2/b-AC nanocomposites to hold an ample potential for photocatalytic hydrogen production from the wastewater.