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The photocatalytic reduction of CO2 to useful products is an area of active research because it shows a potential to be an efficient tool for mitigating climate change. This work investigated the modification of titania with copper(II) nitrate and its impact on improving the CO2 reduction efficiency in a gas-phase batch photoreactor under UV–Vis irradiation. The investigated photocatalysts were prepared by treating P25-copper(II) nitrate suspensions (with various Cu2+ concentrations), alkalized with ammonia water, in a microwave-assisted solvothermal reactor. The titania-based photocatalysts were characterized by SEM, EDS, ICP-OES, XRD and UV-Vis/DR methods. Textural properties were measured by the low-temperature nitrogen adsorption/desorption studies at 77 K. P25 photocatalysts modified with copper(II) nitrate used in the process of carbon dioxide reduction allowed for a higher efficiency both for the photocatalytic reduction of CO2 to CH4 and for the photocatalytic water decomposition to hydrogen as compared to a reference. Similarly, modified samples showed significantly higher selectivity towards methane in the CO2 conversion process than the unmodified sample (a change from 30% for a reference sample to 82% for the P25-R-Cu-0.1 sample after the 6 h process). It was found that smaller loadings of Cu are more beneficial for increasing the photocatalytic activity of a sample. [ABSTRACT FROM AUTHOR]

Copper cobaltite (CuCo2O4) films were synthesized on titanium dioxide (TiO2) and on fluorine‐doped tin oxide (FTO) substrates using a hydrothermal method and characterized by X‐ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and cyclic voltammetry. This research addresses the challenge of hexavalent chromium (Cr(VI)) pollution by employing CuCo2O4/TiO2/FTO as visible light‐active photocatalyst. The films demonstrated strong absorption in the visible spectrum. The heterostructure comprising CuCo2O4 and TiO2 films was synthesized to enhance the photocatalytic reduction of Cr(VI) through synergetic effects. The CuCo2O4/TiO2/FTO film exhibited superior photoreduction performance, achieving photoreduction efficiencies of ∼62.9% under UV‐A and ∼72.3% under visible light, outperforming individual TiO2/FTO and CuCo2O4/FTO films. Reaction rates were 0.00433 min−1 (R2: 0.98893) under UV and 0.00638 min−1 (R2: 0.98787) under visible light, with a half‐life of 1.81 h, indicating significant improvement in photocatalytic activity. However, it is necessary to optimize the synthesis parameters to analyze their impact on its physicochemical properties and its behavior as a photocatalyst. Making possible its applicability is due to the appropriate charge transport, visible light absorption, reduced recombination of electron‐holes pairs, and improved photocatalytic performance. [ABSTRACT FROM AUTHOR]

A new polyoxometalate (POM)-based compound {[Co(H2O)6](H2L)3[H2[(Co0.5W0.5)SiW11O39.5]2} [L = N,N′-bis(3-menthylpyridin-yl)naphthalene-2,6-dicarboxamide], was synthesized using a solvothermal method. In this structure, two [(Co0.5W0.5)SiW11O40] units are linked by co-vertex oxygen to form a bis-Keggin polyoxometalate dimer, which binds to [Co(H2O)6] clusters via hydrogen bonding to form a 1D inorganic chain. The diprotonated organic ligands H2L2+ and the 1D inorganic chains are interconnected by hydrogen bonds to form the 3D supramolecular network. The prepared polyoxometalate compound can be used as a bifunctional material for the electrochemical determination and photocatalytic reduction of Cr(VI) with good performance [LOD: 0.959 μM, reduction rate: 97.5%]. The corresponding anti-interference ability and cycle stability are also studied. [ABSTRACT FROM AUTHOR]

Photocatalytic reduction of 4-nitrophenol to 4-aminophenol has a broad development prospect and potential economic value. In this study, we prepared for the first time Co3O4-modified sulfur-doped polyimide (Co3O4/SPI) catalyst using a facile ion-exchange technique. The chemical structure, morphology and photoelectronic performance of the catalysts were analyzed by different characteristics. The results showed that Co3O4 displayed high dispersibility; increasing the specific surface area of SPI provided more reactive sites. Meanwhile, the Co3O4 modification successfully constructed a Co3O4/SPI type-II heterostructure with a suitable band gap, which significantly improved the absorption of visible light and the photogenerated electron–hole pair separation efficiency of SPI. These factors caused Co3O4/SPI to exhibit higher photocatalytic activity than pure SPI, which facilitated the photocatalytic reduction of 4-nitrophenol to 4-aminophenol by Co3O4/SPI. At 5 min of visible light irradiation, the conversion of 4-nitrophenol was 100%, while that of SPI was 23%. Moreover, the photocatalyst showed good stability after five cycles. Finally, the mechanism of photocatalytic reduction of 4-nitrophenol by Co3O4/SPI was also discussed. The Co3O4/SPI provides a new approach for the cost-effective reduction of 4-nitrophenol and obtains high-value-added 4-aminophenol. [ABSTRACT FROM AUTHOR]

The selective removal and immobilization of uranyl ions from aqueous solutions is essential for the sustainable development of nuclear energy. Herein, a robust lanthanide‐organic framework material (IHEP‐24) is developed for simultaneous fluorescence sensing, selective adsorption, and photocatalytic reduction of uranium, integrating three different functions in one material. The confined space formed by the coordination assembly of viologen derivative ligands and metal‐oxygen clusters can act as precise recognition sites for uranyl, allowing IHEP‐24 to efficiently detect and capture uranyl ions. In addition, the presence of a viologen‐based radical ligand enables IHEP‐24 to a further photocatalytic reduction of the adsorbed uranyl to amorphous UO2. The mechanisms of adsorption and photocatalysis are revealed by batch experiments, photoelectrochemical characterizations, and theoretical calculations. This study provides a reference for the construction of robust multi‐functional MOF materials and also provides support for the deep removal and immobilization of radionuclides from aqueous solution. [ABSTRACT FROM AUTHOR]

This work explores the impact of reaction temperature during thermal exfoliation treatment of bulk-g-C3N4 in the air atmosphere on the structure and performance of the resulting CN photocatalyst. The analysis conducted using XRD, FT-IR, XPS, SEM, and elements mapping tests, illustrated an increase in nitrogen-vacancy and oxygen content on the surface of the CN photocatalyst, resulting in a porous and sparse structure, changes in crystal size, and improved visible light absorption performance. The photocatalytic reduction experiments of hexavalent chromium (Cr(VI)) showed that the CN-540 showed the highest reduction rate of 96.9%, with a reaction rate constant 6.21 times that of bulk-g-C3N4. After 100 min of illumination, the photocatalytic degradation rates of CN-540 for TC-HCl and RhB were 66.7% and 60.6%, respectively. The TOC test results indicated mineralization rates of 51.5% for TC-HCl and 46.6% for RhB. Room temperature fluorescence spectroscopy (PL), transient photocurrent response (TPC), and electrochemical impedance spectroscopy (EIS) measurements confirmed the excellent photogenerated charge carrier separation and transport efficiency of CN-540. The photocatalytic mechanism for reducing Cr(VI) by CN-540 was elucidated based on the active species •OH and •O2 - and Mott-Schottky (M-S) tests. This study provides experimental data for optimizing the photocatalytic performance of g-C3N4 and paves a new way for developing efficient photocatalysts. [ABSTRACT FROM AUTHOR]

Zinc oxide and nickel oxide nanocomposite was successfully synthesized using the co-precipitation technique and evaluated for their photocatalytic efficiency in the degradation of hexavalent chromium. The synthesized nanocomposite was characterized using various techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy to analyze its structure, morphology, chemical bonding, photoabsorption properties, and elemental composition. X-ray diffraction exhibits the presence of zinc oxide, nickel oxide, and zinc oxide and nickel oxide nanocomposite, with average crystallite sizes of 37.92 nm, 56.23 nm, and 41.77 nm, respectively. Fourier transform infrared spectroscopy was used to analyze the chemical composition of zinc oxide and nickel oxide nanocomposite. The ultraviolet–visible spectroscopy exhibited an absorption peak at 447 nm, indicating a bandgap of 2.77 eV. A novel industrial-oriented photoreactor was designed for the reduction of hexavalent chromium under ultraviolet–visible illumination with varying operational parameters. The effectiveness of the experiment was assessed using response surface methodology based on central composite design, which demonstrated a remarkable 95% reduction of hexavalent chromium under optimized conditions. This study validates the accuracy of central composite design in predicting levels of hexavalent chromium reduction. The rate constant for the degradation kinetics of hexavalent chromium was studied to be 0.00450 min−1, indicating adherence to pseudo-second-order kinetics. Additionally, the prepared nanocomposite exhibited significant antibacterial activity against Bacillus subtilis, Escherichia coli, and Pseudomonas putida at different concentrations. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Industrial effluents contain the hazardous metal hexavalent chromium [Cr(VI)], which is potentially lethal to all organisms in the environment. In this work, we developed a transition metal chalcogenide (TMC)-based reduced graphene oxide (rGO) nanocomposite (CeTe/rGO) via the hydrothermal method for the photoreduction of chromium(VI) metal into less hazardous Cr(III). Various analytical tools including x-ray diffraction (XRD), UV–visible spectroscopy (UV–Vis), Brunauer-–Emmett–Teller (BET) and scanning electron microscopy (SEM) analysis were employed for determining characteristics of the CeTe/rGO photocatalyst. The photocatalytic efficiency of transition metal chalcogenide-based rGO nanocomposite was measured under UV–Vis light with a UV–Vis spectrophotometer. The photocatalytic efficiency of CeTe (76.54%) and rGO (81.94%) is smaller than that of the CeTe/rGO (96.50%) due to the larger surface area of the rGO. Scavengers analysis revealed that superoxide anion, hydroxyl radical and holes play a great role in the photocatalysis process. Our results suggest that the CeTe/rGO nanocomposites can potentially be used to reduce the toxic material present in the environment. [ABSTRACT FROM AUTHOR]

The elevated level of carbon dioxide (CO2) in the troposphere is playing a crucial role in changing the earth's climatic system. Excess CO2 concentration is trapping a substantial proportion of heat imparting adverse range of environmental effects like extreme weather events, agricultural impacts and disruption of the ecosystem. Strategies such as CO2 capturing and storage are being pursued using polyoxometalates (POMs) to mitigate the elevated level of CO2 and their efficient conversion into useful chemicals. This review outlines the importance of CO2 reduction by electrocatalytic and photocatalytic reduction of CO2. POMs have several advantages for CO2 activation because of their promising catalytic activity, high selectivity and versatility for incorporating different metal ions and ligands. The efficient redox active metal center facilitates the conversion of CO2 by providing sufficient activation energy. Their robust structure also enables them resist harsh conditions, including high temperature and acidic or basic conditions. Owing to these properties, POMs can be a catalyst, co‐catalyst, photosensitizer or multielectron donor for CO2 reduction. Finally, we stated the challenges and future insight for CO2 activation using POMs. [ABSTRACT FROM AUTHOR]

The utilization of nuclear energy power and nuclear weapon tests not only releases large amounts of radionuclides into environment, but also needs 235U as nuclear fuel for nuclear energy generation. Covalent organic frameworks (COFs) have the advantages of tunable porous structures, adjustable active sites and enough special functional groups, which assure the high selective preconcentration of target radionuclides from complex solutions. In this perspective, the selective extraction of radionuclides (U(VI) as representative cationic ion, Tc(VII) as representative anionic ion, I2 as gaseous nuclide and other nuclides) by COFs through sorption, and photocatalytic strategies are described, and the results show the high efficiency of COFs in target radionuclides removal. The perspective and challenges for the real applications of COFs in future are discussed in the end. Highlights: • Selective sorption of uranium, iodine and pertechnetate was described. • Photoreduction of U(VI) to U(IV) was reviewed and discussed. • The challenges for the real application of COFs in future. [ABSTRACT FROM AUTHOR]

Multicomponent nanomaterials with synergistic effect were typically used to enhance the photocatalytic performance. Herein, three‐component nanomaterials composed of Cu2O, Cu, and TiO2 were prepared using a facile method, and applied in the photocatalytic degradation reactions. The synthetic procedure involves the formation of Cu2O nanoparticle aggregates (NPAs) followed by Cu nanoparticles growth on the surface of Cu2O NPAs in one pot, and TiO2 encapsulation (Cu2O‐Cu@TiO2). The catalyst structure was characterized by x‐ray diffraction, field emission‐scanning electron microscopy, transmission electron microscopy, and energy‐dispersed x‐ray. The catalytic performance of Cu2O‐Cu@TiO2 NPAs was evaluated through the photocatalytic degradation of 4‐nitrophenol under the simulated solar light. We found that it exhibited greater activity than the Cu2O‐Cu NPAs, commercial TiO2, and Cu2O@TiO2 NPAs, probably due to their synergistic interactions resulting in the effective photogenerated carrier transfer in the multicomponent nanomaterials. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Photocatalytic reduction of Cr(VI) to Cr(III) is one of the most promising technologies to remove Cr(VI) pollution because of its environmental friendliness, cost‐effective and energy saving. In this experiment, two‐dimensional Bi2MoO6(BMO) nanosheets and cerium‐based MOFs UiO‐66(Ce) were synthesized by solvent thermal method, and in the presence of BMO, the UiO/BMO‐x heterojunction composites were constructed in situ to explore its photocatalytic reduction properties of Cr(VI). The experiment showed that 4 mM of Cr (VI) solution could be reduced 100 % to Cr (VI) by 15 mg catalyst under optimal reaction conditions. The composite photocatalyst prepared in this experiment can realize the green treatment of Cr(VI) in the environment under photocatalytic conditions, and has potential application value in the remediation of heavy metal pollution. [ABSTRACT FROM AUTHOR]

Rare-earth perovskite oxides have become a research hotspot in the fields of environment and energy owing to their structural tunability, excellent redox properties, high stability and high catalytic activity. Researchers have designed and developed different rare-earth perovskite catalysts for tackling environmental pollutants in recent years. This review summarizes recent research progress on rare-earth perovskite catalysts in the catalytic oxidation and photocatalytic degradation of pollutants, gas sensing of volatile organic compounds and photocatalytic water splitting for hydrogen production and carbon dioxide reduction and conversion, and summarizes the mechanism of these reactions. It also discusses in detail the relationship between structural modification, synthesis process and the physical–chemical properties of the catalysts. Finally, the challenges with rare-earth chalcocite catalysts in the field of environment and energy are discussed. This paper reviews recent progress in rare-earth perovskite oxide materials, explores the effects of capacity factors, lattice defects, different metal active centers and perovskite modifications on crystal structure and applied properties, discusses the effects of synthesis processes (sol-gel, co-precipitation, microemulsion, hydrothermal, high-temperature) on their physical and chemical properties, and summarizes their applications in pollutant catalytic oxidation and photocatalytic degradation, VOCs gas sensing, and photocatalytic splitting of water for hydrogen production and carbon dioxide reduction and conversion. (Image credit: P. Li.) [ABSTRACT FROM AUTHOR]

Elemental doping can improve the photocatalytic activity of bulk graphitic carbon nitride (g-C3N4) under visible-light. In this study, sulfur and oxygen co-doped g-C3N4 (x% S-g-C3N4) was fabricated through thermal polymerization of macromolecular precursor obtained from hydrothermal pretreatment. The prepared photocatalysts, including g-C3N4, hydrothermally treated g-C3N4 (g-C3N4-HT), and x% S-g-C3N4, were analyzed under various conditions. Their ability to reduce Cr(VI) through photocatalytic reduction was evaluated comprehensively, taking into account the influence of catalyst dose, presence of inorganic anions, initial concentration and initial pH of Cr(VI) solution. The results showed that x% S-g-C3N4 (3% S-g-C3N4) possesses superior photocatalytic reduction activity to g-C3N4 and g-C3N4-HT, largely due to the co-doping. This co-doping strategy enhances the light harvesting capacity by modifying the electronic band structure of g-C3N4, and accelerates the excitons transfer and separation by optimizing its photoelectric properties. Additionally, the three-dimensional structure formed during preparation process enhances the stability and reusability of g-C3N4. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) transformation is a cutting-edge technology to eliminate greenhouse effects and produce valuable chemicals as well as fuels. Herein, we report an elaborate engineering for improving the efficiency of Zr-based Bipy-UiO-67 metal–organic framework (ZBU) in CO2 transformations. As demonstrated, tuning the catalytic performance by incorporating Co into ZBU (ZBU-Co) was realized as a practical strategy to affect the CO2 insertion to epoxides in terms of conversion, green procedure, recyclability, chemical/thermal stability, time, and energy. Also, extending the diversity of the reaction to bulky epoxides showed that increasing temperature is an effective remedy for achieving complete conversion. Importantly, in comparison with the homogeneous and heterogeneous counterparts, ZBU-Co illustrated superior results. On the other hand, ZBU-Co exhibited potential application in photocatalytic reduction of CO2, endowing bi-functional feature to the catalytic system. Accordingly, higher CO2 adsorption capacity and CO evolution were recorded for ZBU-Co compared to the pristine ZBU. Furthermore, the ability to recover the catalyst for four cycles is a valuable characteristic from environmentally/eco-friendly aspects, which further proves the versatility of the modified MOF in the photocatalytic reaction. Overall, ZBU-Co is considered a promising candidate for CO2 transformations due to the several advantages in CO2 insertion and photocatalytic reduction. [ABSTRACT FROM AUTHOR]

Prevention and management of water pollution are becoming a great challenge in the present scenario. Different conventional methods like carbon adsorption, ion exchange, chemical precipitation, evaporation, and biological treatments remove water pollutants. Nowadays, the requirement for effective, non-toxic and safe waste management strategies is very high. Nanomaterials have been explored in various fields due to their unique characteristics. Green synthesis of nanomaterial is becoming more popular due to their safety, non-toxicity, and ease of scale-up technology. Metal nanoparticles can be synthesized using a green synthesis method using biological sources provided by eco-friendly, non-hazardous nanomaterials with superior properties to bulk metals. Hence, this study has designed a green synthesis of magnetic (cobalt oxide) and noble (gold) nanoparticles from the fresh flowers of Clitoria ternatea. The flavonoids and polyphenols in the extract decreased the energy band gap of cobalt oxide and gold nanoparticles; hence, the capping of the natural constituents in Clitoria ternatea helped form stable metal nanoparticles. The cobalt oxide and gold nanoparticles are evaluated for their potential for eliminating organic pollutants from industrial effluent. The novelty of this present work represents the application of cobalt oxide nanoparticles in the removal of organic pollutants and a comparative study of the catalytic behaviour of both metal nanoparticles. The degradation of bromophenol blue, bromocresol green, and 4–nitrophenol in the presence of gold nanoparticles was completed in 120, 45, and 20 min with rate constants of 3.7 × 10−3/min, 6.9 × 10−3/min, and 16.5 × 10−3/min, respectively. Similarly, the photocatalysis of bromophenol blue, bromocresol green, and 4–nitrophenol in the presence of cobalt oxide nanoparticles was achieved in 60, 90, and 40 min with rate constants of 2.3 × 10−3/min, 1.8 × 10−3/min, and 1.7 × 10−3/min, respectively. The coefficient of correlation (R2) values justify that the degradation of organic pollutants follows first-order kinetics. The significance of the study is to develop green nanomaterials that can be used efficiently to remove organic pollutants in wastewater using a cost-effective method with minimal toxicity to aquatic animals. It has proved to be useful in environmental pollution management.

In this work, TiO2-based composite photocatalysts were synthesized for the photoreduction of Cr(VI) by deposition of CdS and/or Cu nanoparticles. Oak leaf extract was used as a reducing agent for the synthesis of Cu nanoparticles. Although the deposited amount of Cu was small (~ 1.1 wt%), it resulted in a shift of the absorption edge to the visible region and a significantly higher efficiency compared to TiO2. Deposition of ~ 3 wt% CdS resulted also in a higher activity under the visible light compared to TiO2, but lower compared to Cu-TiO2. The best results were obtained with the ternary photocatalyst, probably due to the formation of a z-scheme in which the deposited Cu acts as a mediator for electron transfer between CdS and TiO2. The addition of citric acid as a hole "scavenger" allowed a further increase in activity, even in the case of TiO2.

Abstract The enhancement of the photocatalytic performance of pristine WO3 was systematically adjusted due to its fast recombination rate and low reduction potential. A designed heterostructure photocatalyst was necessarily synthesised by Fe3+ metal ions doping into WO3 structure with and composition modification. In this study, we synthesised a retrievable Fe-doped WO3/SiO2 heterostructure using a surfactant-assisted hydrothermal method. This heterostructure was then employed as an effective photocatalyst for the removal of Cr(VI) under visible light irradiation. Enlarged photocatalytic reduction was observed over a synergetic 7.5 mol% Fe-doped WO3/SiO2-20 nanocomposite, resulting in dramatically increased activity compared with undoped WO3 and SiO2 nanomaterials under visible light illumination within 90 min. The presence of 7.5 mol% Fe3+ ion dopant in WO3 optimised electron–hole recombination, consequently reducing WO3 photocorrosion. After adding SiO2 nanoparticles, the binary WO3-SiO2 nanocomposite played roles as both adsorbent and photocatalyst to increase specific surface area. Thus, the 7.5 mol% Fe-doped WO3/SiO2-20 nanocomposite catalyst had more active sites on the surface of catalyst, and enhanced photocatalytic reduction was significantly achieved. The results showed 91.1% photocatalytic reduction over the optimum photocatalyst, with a photoreduction kinetic rate of 21.1 × 10–3 min−1, which was approximately four times faster than pristine WO3. Therefore, the superior optimal photocatalyst demonstrated reusability, with activities decreasing by only 9.8% after five cycles. The high photocatalytic performance and excellent stability of our photocatalyst indicate great potential for water pollution treatments.

The enhancement of the photocatalytic performance of pristine WO3 was systematically adjusted due to its fast recombination rate and low reduction potential. A designed heterostructure photocatalyst was necessarily synthesised by Fe3+ metal ions doping into WO3 structure with and composition modification. In this study, we synthesised a retrievable Fe-doped WO3/SiO2 heterostructure using a surfactant-assisted hydrothermal method. This heterostructure was then employed as an effective photocatalyst for the removal of Cr(VI) under visible light irradiation. Enlarged photocatalytic reduction was observed over a synergetic 7.5 mol% Fe-doped WO3/SiO2-20 nanocomposite, resulting in dramatically increased activity compared with undoped WO3 and SiO2 nanomaterials under visible light illumination within 90 min. The presence of 7.5 mol% Fe3+ ion dopant in WO3 optimised electron–hole recombination, consequently reducing WO3 photocorrosion. After adding SiO2 nanoparticles, the binary WO3-SiO2 nanocomposite played roles as both adsorbent and photocatalyst to increase specific surface area. Thus, the 7.5 mol% Fe-doped WO3/SiO2-20 nanocomposite catalyst had more active sites on the surface of catalyst, and enhanced photocatalytic reduction was significantly achieved. The results showed 91.1% photocatalytic reduction over the optimum photocatalyst, with a photoreduction kinetic rate of 21.1 × 10–3 min−1, which was approximately four times faster than pristine WO3. Therefore, the superior optimal photocatalyst demonstrated reusability, with activities decreasing by only 9.8% after five cycles. The high photocatalytic performance and excellent stability of our photocatalyst indicate great potential for water pollution treatments. [ABSTRACT FROM AUTHOR]

The synergistic removal of various pollutants is the challenge of environmental remediation due to mutual interference. The effect of Cr(VI) and tetracycline (TC) on photocatalytic reduction of U(VI) by MoS 2 /g-C 3 N 4 was investigated by batch and spectroscopic techniques. The high adsorption of U(VI) on MoS 2 /g-C 3 N 4 and the negative influence of photo-irradiation on U(VI) removal at pH 4.5 were observed. The batch experiments showed that the presence of TC and Cr(VI) improved the photoreduction of U(VI), whereas photocatalytic removal of Cr(VI) and TC were not influenced significantly. The adsorbed U(VI) was primarily photo-reduced into U(IV), while U(IV) was re-oxidized into U(VI) with further increasing irradiation by XPS analysis. According to quenching experiments, photo-degradation of TC was attributed to photogenerated holes, while the photo-reduction of Cr(VI) and U(VI) were due to •O 2 − and •OH radicals, respectively. These findings are crucial for the application of g-C 3 N 4 -bearing composites in the synergistic removal of radionuclide, heavy metal and organic at actual environmental cleanup. [ABSTRACT FROM AUTHOR]

A series of nano-photocatalysts metal-organic frameworks (MOFs)/graphitic carbon nitride (CN) (named MOFCN- x) with high activity have been synthesized by in-situ growth method. Under visible light irradiation, MOFCN- x hybrids show enhanced photocatalytic activity for the debromination of polybromodiphenyl ethers (PBDEs) compared with CN. Among all the hybrids, MOFCN-2 shows the highest reaction rate, which is 3.3 times as high as that in CN. MOFCN- x photocatalysts own stable visible light activity after recycled experiment. It indicates that a moderate amount of MOFs in MOFCN- x can largely enhance the photocatalytic ability by improved visible light absorption, larger specific surface area and better photo-generated charge carriers separation and transfer capabilities. More interestingly, the debromination pathway of PBDEs by MOFCN- x shows obvious selectivity compared with pure CN that bromines at meta -positions are much more susceptible than those at the para - and ortho -positions. The possible photoreductive mechanism has been proposed. This study shows that nanocomposite MOFCN can be an excellent candidate for dealing with halogen pollutants by solar-driven. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] Converting CO 2 into chemicals and fuels by solar energy can alleviate global warming and solve the energy crisis. In this work, CoAl-LDO/MoO 3−x (LDO/MO) composites were successfully prepared and achieved efficient CO 2 reduction under visible light. The CoAl-layered double oxides (CoAl-LDO) evolved from CoAl-layered double hydroxide (CoAl-LDH) exhibited a more robust structure, broader light absorption, and improved CO 2 adsorption ability. The local surface plasmon resonance (LSPR) effect excited by nonstoichiometric MoO 3−x broadened the photo-response range of CoAl-LDO/MoO 3−x. In addition, constructing step-scheme (S-scheme) heterojunctions could simultaneously optimize the migration mechanism of photogenerated electrons and holes, and retain carriers with strong redox ability. Therefore, the production rates of CO and CH 4 on the optimal LDO/MO composite were 7 and 9 times higher than the pristine CoAl-LDH, respectively. This work hybridizes oxidation photocatalysts and LDO-based materials to optimize the charge separation and migration mechanisms, which guides the modification of LDO-based materials. [ABSTRACT FROM AUTHOR]

The combination of zerovalent iron (Fe0) and titanium dioxide (TiO2) has been investigated as a promising method for environmental remediation. However, it is a challenge to prepare conveniently desirable Fe0/TiO2 nanocomposites with excellent efficiency and reusability. Here, a novel nanocomposite material, Fe0/TiO2@D201, was synthesized to enhance the removal of Cr(VI) from an aqueous system by impregnating Fe0 and TiO2 inside a commercial anion exchanger (D201). The proposed structure and Cr(VI) removal mechanism of Fe0/TiO2@D201 were confirmed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. Compared to the monometallic samples (Fe0-D201 and TiO2-D201), Fe0/TiO2@D201 showed outstanding Cr(VI) removal and the removal ratio reached up to 97.30% after 120 min of UV light irradiation. The removal of Cr(VI) by Fe0/TiO2@D201 remained high (91.70%) even after four cycles, indicating the stability of the nanocomposites toward Cr(VI) removal and their strong potential for practical applications. The addition of ethylenediaminetetraacetic acid (EDTA) positively affected the Cr(VI) reduction process, whereas the addition of Na2S2O8 negatively affected the Cr(VI) process. The XPS results revealed that the photocatalytic reduction of Cr(VI) by Fe0/TiO2@D201 involved the capture of photoexcited electrons and Fe0 reduction. A path for the photogenerated electrons engaging in the reduction reaction to improve the utilization of Fe0 was proposed. These results demonstrate that Fe0/TiO2@D201 is a promising alternative composite catalyst for the efficient Cr(VI) removal from contaminated water. [ABSTRACT FROM AUTHOR]

Tea waste biochar/graphitic carbon nitride (TBC/g-C3N4) composites were prepared by high temperature thermal polymerization with tea waste as raw material and melamine as precursor. The morphology, structure and photoelectric characteristics of the photocatalysts were characterized by SEM, XRD, XPS, UV-Vis DRS, PL and EIS.The performance of TBC/g-C3N4 composites for photocatalytic reduction of U(Ⅵ) under visible light irradiation was studied, and the mechanism of photocatalytic reduction of U(Ⅵ) by TBC/g-C3N4 composites was discussed.The results show that when the mass fraction of TBC is 5%, the initial pH value is 4 and the amount of catalyst is 1 g/L, the removal rate of U(Ⅵ) by TBC/g-C3N4 composites is 99.64% after visible light irradiation for 30 min, which is much higher than that of g-C3N4 (58.8%).The removal rate of U(Ⅵ) is above 80% after five cycles, which indicates that TBC/g-C3N4 composites has an excellent photocatalytic stability.The addition of TBC makes the band gap of g-C3N4 reduced from 2.63 eV to 2.14 eV, widens the visible light absorption range, promotes the separation of photogenerated charge, reduces the recombination rate of photogenerated electron-hole pair, and thus enhances the photocatalytic activity of TBC/g-C3N4composites.This study provides a new idea to design and synthesizethe photocatalysts with efficient, low-cost and environmentally-friendly.

Titanium dioxide (Titania) nanoparticle-coated biochar derived through co-pyrolysis of COVID-19 waste face mask (WFM) and Moringa oleifera seed cake (MO) provides an effective way to alleviate toxic metal in wastewater. This study investigates the effects of Biochar/titania photocatalyst preparation, characterization, and its photoreduction of Cr(VI). The morphological and functional modifications in the catalyst were identified using X-Ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, ultraviolet spectrophotometer, surface area analysis, and Raman spectrophotometer, respectively. The influencing parameters, namely, pH, photocatalyst dosage, initial pollutant concentration, and visible light irradiation time, have been investigated. The findings reveal that the Cr(VI) reduction by the photocatalyst was highly facilitated by photocatalytic process. The prepared photocatalyst shows higher and faster reduction rate of Cr(VI) and also improves the catalyst stability. The photoreduction of Cr(VI) ensembles well with pseudo-first order kinetics. At 180 min of reaction time, maximum Cr(VI) reduction of 98.65% was achieved at pH 2, 0.3 g/L catalyst dosage, and 10 ppm initial concentration, respectively. The synthesized photocatalyst shows excellent recycling performance up to 7 times, and these studies proved that the prepared catalyst is cost-effective and efficiently employed for removing pollutants. [ABSTRACT FROM AUTHOR]

The photocatalytic reduction of Cr6+ to Cr3+ in an aqueous solution, using 3 wt% Ag/g-C3N4 in the presence of ethylenediaminetetraacetic acid (EDTA), has been investigated here. The photocatalytic reduction of Cr6+ with pure g-C3N4 was very low. The addition of Ag and EDTA can significantly improve the photocatalytic reduction of Cr6+ using g-C3N4. In the presence of EDTA, the efficiency with Ag/g-C3N4 was better than those with Au/g-C3N4 and Cu/g-C3N4. With EDTA, the reduction rate constant increased from 0.0005 for pure g-C3N4 to 0.12 min−1 for 3 wt% Ag/g-C3N4. By increasing the concentration of EDTA from 0 to 500 mg L−1, the reduction efficiency of Cr6+ increased extremely, and the rate constant raised from 0.008 to 0.12 min−1. The optimal EDTA concentration was 500 mg L−1 for the photocatalyst Ag/g-C3N4. The Ag-EDTA complex may be reduced to metallic silver by the conduction band electrons of g-C3N4. The electron–hole recombination was significantly suppressed by the electron trapping of Ag. EDTA may act in by the formation of Cr3+-complex and the separation of Cr3+ from the g-C3N4 surface and by the valence band hole scavenger of g-C3N4. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectra (PL) were used to characterize g-C3N4 and Ag/g-C3N4 nanoparticles. A possible mechanism for photocatalytic Cr6+ reduction has also been demonstrated. [ABSTRACT FROM AUTHOR]

The optimization of photocatalysis is complex, as heterogenous catalysis makes its kinetic modeling or design of experiment (DOE) significantly more difficult than homogeneous reactions. On the other hand, Bayesian optimization (BO) has been found to be efficient in the optimization of many complex chemical problems but has rarely been studied in photocatalysis. In this paper, we developed a BO platform and applied it to the optimization of three photocatalytic CO2 reduction systems that have been kinetically modeled in previous studies. Three decision variables, namely, partial pressure of CO2, partial pressure of H2O, and reaction time, were used to optimize the reaction rate. We first compared BO with the traditional DOE methods in the Khalilzadeh and Tan systems and found that the optimized reaction rates predicted by BO were 0.7% and 11.0% higher, respectively, than the best results of optimization by DOE, and were significantly better than the original experimental data, which were 1.9% and 13.6% higher, respectively. In both systems, we also explored the best combination of the surrogate model and acquisition function for BO, and the results showed that the combination of Gaussian processes (GP) and upper confidence bound (UCB) had the most stable search performance. Furthermore, the Thompson system with time dependence was optimized with BO according to the selectivity of CH4. The results showed that the optimized reaction time of BO agreed with the actual experimental data with an error of less than 5%. These results suggest that BO is a more promising alternative to kinetic modeling or traditional DOE in the efficient optimization of photocatalytic reduction. [ABSTRACT FROM AUTHOR]

Recently, the bismuth‐rich strategy via increasing the bismuth content has been becoming one of the most appealing approaches to improve the photocatalytic performance of bismuth oxyhalides. However, insights into the mechanism behind the encouraging experiments are missing. Herein, we report the results of the theory‐led comprehensive picture of bismuth‐rich strategy in bismuth oxyhalide photocatalysts, selecting Bi5O7X (X = F, Cl, Br, I) as a prototype. First‐principle calculations revealed that the strategy enables good n‐type conductivity, large intrinsic internal electric field, high photoreduction ability and outstanding harvest of visible light, and particularly ranked the intrinsic activity of this family: Bi5O7F > Bi5O7I > Bi5O7Br > Bi5O7Cl. Designed experiments confirmed the theoretical predictions, and together, these results are expected to aid future development of advanced photocatalysts. [ABSTRACT FROM AUTHOR]

The synergistic effect of bimetallic co‐incorporated metal oxides have gained enormous attention due to their unique optoelectronic properties. Herein, we present the green synthesis of ZnO, Cu‐incorporated ZnO, Mn‐incorporated ZnO, and Cu‐Mn co‐incorporated nanoparticles (ZnO NPs, CuZnO NPs, MnZnO NPs, MnCuZnO NPs) for antimicrobial and photocatalytic reduction applications using corn silk extract and industrial metal wastes. The as‐synthesized NPs were characterized by using UV‐visible absorption spectroscopy (UV‐Vis), photoluminescence (PL) spectroscopy, Fourier‐transformed infrared spectroscopy (FT‐IR), powdered x‐ray diffraction (XRD), and scanning electron microscopy (SEM). CuZnO, MnZnO, and MnCuZnO NPs efficiently inhibited bacterial culture growth. The photocatalytic reduction activity of as‐synthesized NPs against the different concentrations of 4‐nitrophenol (4‐NP) in water was also investigated. CuZnO and MnCuZnO nanoparticles were to be efficient photocatalysts for reducing 4‐NP into 4‐aminophenol (4‐AP). Research Highlights: Green synthesis of nanomaterials by agricultural and industrial wastesCu and Mn co‐incorporated ZnO NPs have shown good photocatalysis and antimicrobial activitiesGreen approach for waste conversion to value‐added products [ABSTRACT FROM AUTHOR]