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Due to severe environmental and health risks associated with Cr(VI), there is an urgent need to prioritize the development of new and efficient photocatalysts for its reduction. To solve this issue, three different nanocomposites (NCs) of Zinc oxide (ZnO) with Graphene oxide (GO), i.e. ZnO/@GO were prepared via hydrothermal process, by varying GO concentrations (10, 20, and 30 wt%). The goal is to investigate the impact of GO concentration on the photoreduction of Cr(VI) to Cr (III) in an aqueous system. Various physical properties such as crystallinity, morphology, elemental composition, and optical characteristics of the samples were analyzed using Powder X-ray diffraction (P-XRD), Scanning electron microscopy with Energy dispersive X-ray (SEM–EDX), Ultraviolet–Visible spectroscopy (UV–VIS), Diffuse reflectance spectroscopy, and Photoluminescence spectra, respectively. Photocatalytic reduction of Cr(VI) to Cr (III) was investigated using prepared different ZnO/@GO NCs samples under solar light illumination at room temperature within a pH range of 5.0–6.0. Notably, the highest reduction of 95% was achieved with 10 wt% GO-doped ZnO NCs (ZnO/@10 wt% GO NCs). Kinetic analysis reported the pseudo second-order model and rate constants were found to be 0.349, 0.0123, and 0.001 mol−1L−11 min−1 for the used three different composites, respectively. This data indicates a confirmed decline in the reduction of Cr(VI) to Cr (III) with the increasing concentration of GO in prepared NCs. In last, reduction mechanism was examined which confined the role of ̇OH species in the conversion of Cr(VI) to Cr (III). [ABSTRACT FROM AUTHOR]

This review provides a comprehensive analysis of the rapidly evolving field of solar-driven carbon dioxide (CO2) conversion, focusing on recent developments and future prospects. While significant progress has been made in understanding the fundamental mechanisms of photocatalytic (PC), photoelectrocatalytic, photobiocatalytic, and photothermal CO2 reduction, the efficient and scalable utilization of these technologies remains a challenge. The analysis critically examines the latest advancements in materials and catalysts, including light-harvesting centers, charge transfer interfaces, and catalytically active sites, highlighting their critical role in optimizing efficiency and selectivity. This study examines the recent progress made in PC, photoelectrochemical, and photovoltaic-electrochemical devices, identifying key challenges and opportunities for future research. By highlighting the gap between current research and practical applications, this review aims to provide valuable insights for the development of sustainable and cost-effective technologies for CO2 conversion, contributing to a cleaner and more sustainable energy future. [ABSTRACT FROM AUTHOR]

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]

The photocatalytic activity of tin dioxide (SnO2) is limited due to its inadequate response to the solar spectrum, wide band gap, and low visible light photocatalytic activity. Here, we synthesized conjugated polyvinyl alcohol (CPVA) modified tin dioxide (CPVA/SnO2) through in-situ hydrothermal synthesis and evaluated its performance for photocatalytic reduction of hexavalent chromium Cr(VI). A series of testing and characterization results revealed that CPVA was uniformly coated on the surface of SnO2, forming a mesoporous CPVA/SnO2 heterojunction with enhanced crystallinity and reduced oxygen defects, which resulted in an expanded light absorption range towards the red light region. The reaction rate constant of CPVA/SnO2-A for photocatalytic reduction of Cr(VI) under visible light (0.060 min-1) was 6 times higher than that of homemade CPVA/TiO2 and 2.87 times higher than that of SnO2 for the photocatalytic reduction of Cr(VI) under UV light (0.0209 min-1). The photocatalytic mechanism indicates that CPVA/SnO2 exhibited significantly enhanced performance under UV-light irradiation by forming a type II heterojunction. When CPVA/SnO2 was exposed to visible light, photogenerated electrons on the lowest unoccupied molecular orbital (LUMO) of CPVA were efficiently transferred to the surface of SnO2 through the CPVA/SnO2 heterojunction, reducing electron-hole recombination while also photosensitizing the photocatalyst and promoting efficient photocatalysis under visible light illumination. Ultimately, this process effectively reduces Cr(VI) to Cr(III). [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]

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]

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]

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]

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]

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.