Robust Photocatalyst Research Articles

Nanocomposite of waterborne hyperbranched polyester and clay@carbon dot as a robust photocatalyst for environmental remediation

In this study, eco-friendly high performing waterborne hyperbranched polyester nanocomposites with different doses of clay@carbon dot nanohybrid were fabricated for the first time through an in situ polymerization technique in absence of any solvent and compatibilizing agent. X-ray diffractometeric (XRD), Fourier transform infrared spectroscopic (FTIR) and transmission electron microscopic (TEM) analyses support the formation of nanocomposite. XRD confirmed the absence of d001 reflections of bentonite clay while TEM study revealed the partial exfoliation of the layers by the polyester chains. The thermoset of this nanocomposite with hyperbranched epoxy of glycerol and poly(amido amine) showed an appreciable improvement in tensile strength (7.8–35.7 MPa), scratch hardness (4–>10 kg), impact resistance (>8.3–>10 kJ/m), Young's modulus (245–340 MPa), toughness (17.18–49.89 MJ/m3) and thermal stability (by 32 °C) compared to the pristine system. The nanocomposite also exhibited a high adsorption capacity (90.9 mg/g) of Pb(II) ions. Further, the nanocomposite was also used as a visible light active photocatalyst for removal of organic dye like Rodamine B. In addition, the nanocomposite exhibited biodegradability behavior against Pseudomonus aerugionosa bacterial strain. Thus, the nanocomposite is an exceptionally promising candidate as an environmentally friendly, low-cost and effectual adsorbent for the elimination of contaminants from the atmosphere.

A bismuth rich hollow Bi4O5Br2 photocatalyst enables dramatic CO2 reduction activity

The insufficient separation of photogenerated charge carriers and faint CO2 capture remains the major obstacles for photocatalytic conversion of CO2 into solar fuel. Rational design of semiconductor photocatalysts with unique structures may be promising to break this bottleneck. Herein, bismuth rich Bi4O5B2 hollow microspheres are designed as a robust photocatalyst for efficient CO2 reduction. Thanks to the bismuth rich strategy, the highly dispersed band structure and the elevated conduction band (CB) potential facilitate the charge transfer and photoreduction ability. Meanwhile, hollow structure provides the large specific area and creates a resonance in its interior to enhance the CO2 adsorption and activation. Benefiting from the collaborative promotion effect, the local charge arrangement and electronic structure are tuned so as to an exceptional efficiency of photocatalytic CO2 conversion into CO (3.16 μmol g−1 h−1) and CH4 (0.5 μmol g−1 h−1) is attained over hollow Bi4O5Br2, which is superior to that of solid Bi4O5Br2 and BiOBr, as well as other reported Bi-based photocatalysts. This work paves new opportunities for exploring high-efficiency CO2 photoreduction catalysts.

Robust photocatalyst does double duty

Light-activated catalysts are increasingly used in reduction-oxidation reactions, generating radicals that selectively modify complex molecules. But most such photoredox catalysts rely on expensive, scarce metals like iridium and rubidium. Many are vulnerable to harsh reagents, and different reactions usually need custom catalysts. Chemists in Germany have developed an alternative that not only is cheap and stable but also can catalyze a broad range of radical-based redox reactions. The catalyst is a solid semiconductor material called mesoporous graphitic carbon nitride, an extended network of triazine-based aromatic rings that is easily prepared from cyanamide (Science 2019, DOI: 10.1126/science.aaw3254). “We believe it offers a significant improvement,” says Burkhard Konig at the University of Regensburg, part of the research team. Blue light separates charges on the catalyst’s surface, generating electrons that drive reduction reactions, and holes that handle oxidation reactions. This allows the catal...

Ultra-small cobalt nanocrystals embedded in 2D-MoS2 nano-sheets as efficient co-catalyst for solar-driven hydrogen production: Study of evolution rate dependence on cobalt nanocrystal size

2D-MoS2 nanostructures are attractive co-catalysts for photocatalytic hydrogen evolution due to their suitable water reduction potentials and high stability. However, the catalytic activity of MoS2 is greatly limited by the catalytically inert basal planes. Doping of transition-metal ions into MoS2 structure is an effective way to activating the basal planes. To this end, the formation of size-controlled metal nanocrystals with clean surface and mono dispersed nature is a current challenge. Here we utilized pulsed laser ablation in liquid approach to generate high purity size controlled cobalt nanocrystal by adjusting the laser fluences and systematically evaluate the effect of cobalt nanocrystals size and concentration on MoS2 to activate the basal planes. A set of Co-MoS2/CdS nanorods with different cobalt size were examined, and an optimal cobalt size of 3.1 nm was obtained. The optimized CdS/Co-MoS2 nanocomposite showed a very high H2 production rate (275 mmol h−1 g−1) with outstanding stability. To the best of our knowledge, this is the best performance reported for CdS/MoS2 based nanocomposites. The remarkable hydrogen evolution rate and stability may be due to reduced recombination rate and greatly increased density of catalytic active sites which is determined by photoluminescence and impedance spectroscopy. Finally, we believe that the strategies applied in the present study to form robust photocatalysts and its utilization in solar driven hydrogen production would inspire the development of other low-cost photocatalysts for renewable fuel production.

Engineering the performance of heterogeneous WO3/fullerene@Ni3B/Ni(OH)2 Photocatalysts for Hydrogen Generation

The hydrogen production through solar water splitting could be eco-friendly, environmental-benign and sustainable, alternative to fossil fuels energy carriers. In this work, the novel heterojunction WO3/fullerene/Ni3B/Ni(OH)2 composites were successfully fabricated through different methods. The Ni3B/Ni(OH)2 as a needle like nanostructures were integrated into the interfaces between WO3 and fullerene. The structural phase and morphology of prepared nanomaterials were significantly modified by incorporating the Ni3B/Ni(OH)2 as a co-catalyst. The results demonstrated that dopant element serves as the conductive electron bridges, rather than general cocatalyst, to accumulate electrons and inspire the H2 generation kinetics over pure WO3 photocatalyst. The significantly improved hydrogen rate of evolution up to 1578 μmol h−1 g−1 was found for hybrid photocatalyst [WO3/fullerene@ 1.5% Ni3B/Ni(OH)2] which was 9.6 times higher as compared to pure photocatalyst. The interfacial contact between co-catalyst and composite could play substantial role in effective separation and transference of charge-carriers for improved hydrogen evolution rate. Under the visible light illumination, the heterojunction nanostructures inspire rapid transfer of electrons from WO3 towards Ni3B/Ni(OH)2 to inhibit the fast recombination rate and prolong the WO3 charge-carrier's lifetime, thereby releasing more electrons with greater reducing power for hydrogen production. This work may open an avenue for the strategy and green preparation of robust photocatalysts for scalable applications in solar H2 evolution and sustainable environment.

Atomically Dispersed Single Co Sites in Zeolitic Imidazole Frameworks Promoting High-Efficiency Visible-Light-Driven Hydrogen Production.

As photocatalysis technology could transform renewable and clean solar energy into green hydrogen (H2 ) energy through solar water splitting, it is regarded as the "Holy Grail" in chemistry field in the 21st century. Unfortunately, the bottleneck of this technique still lies in the exploration of highly active, cost-effective, and robust photocatalysts. This work reports the design and synthesis of a novel zeolitic imidazole framework (ZIF) coupled Zn0.8 Cd0.2 S hetero-structured photocatalyst for high-performance visible-light-induced H2 production. State-of-the-art characterizations and theoretical computations disclose that the interfacial electronic interaction between ZIF and Zn0.8 Cd0.2 S, the high distribution of Zn0.8 Cd0.2 S on ZIF, and the atomically dispersed coordinately unsaturated Co sites in ZIF synergistically arouse the significantly improved visible-light photocatalytic H2 production performance.

Hierarchical Nanostructured Photocatalysts for CO2 Photoreduction

Practical implementation of CO2 photoreduction technologies requires low-cost, highly efficient, and robust photocatalysts. High surface area photocatalysts are notable in that they offer abundant active sites and enhanced light harvesting. Here we summarize the progress in CO2 photoreduction with respect to synthesis and application of hierarchical nanostructured photocatalysts.

Solid-State, Low-Cost, and Green Synthesis and Robust Photochemical Hydrogen Evolution Performance of Ternary TiO2/MgTiO3/C Photocatalysts

SummarySolar-driven photochemical hydrogen evolution is a promising route to sustainable hydrogen fuel production. Large-scale preparation of highly active photocatalysts using elementally abundant and less-expensive materials is urgently required for widespread practical application. Here, we report a highly efficient and low-cost TiO2/MgTiO3/C heterostructure photocatalyst for photochemical water splitting, which was synthesized on gram scale via a facile mechanochemical method. The heterostructure and carbon sensitization offer excellent photoconversion efficiency as well as good photostability. Under irradiation of one AM 1.5G sunlight, the optimal TiO2/MgTiO3/C photocatalyst can show a great solar-driven hydrogen evolution rate (33.3 mmol·h−1·g−1), which is much higher than the best yields ever reported for MgTiO3-related photocatalysts or pure TiO2 (P-25). We hope this work will attract more attention to inspire further work by others for the development of low-cost, efficient, and robust photocatalysts for producing hydrogen in artificial photosynthetic systems.

Carbon Quantum Dot/TiO2 Nanohybrids: Efficient Photocatalysts for Hydrogen Generation via Intimate Contact and Efficient Charge Separation

We report a facile synthesis of carbon quantum dot (CQD)-sensitized TiO2/Pt nanocomposites as efficient and robust photocatalysts for light-driven proton reduction from water. We show that this met...

N-hydroxyphthalimide-TiO2 complex visible light photocatalysis

TiO2 is the most established semiconductor photocatalyst. The prominence of TiO2 is becoming increasingly obvious because its interfacial redox reactions have implication on a wide range processes such as energy conversion and environmental remediation. Herein, we exploited the surface complex created by the interaction between organic molecules with binding sites and accommodating surface of TiO2 for visible light-driven selective aerobic oxidation reactions. A novel surface complex formed between N-hydroxyphthalimide (NHPI) and TiO2 was discovered. The NHPI-TiO2 complex turned out to be an outstanding visible light photocatalyst and was successfully used in the selective oxidation of amines into imines with atmosphere O2 under blue LED irradiation. The stability of the NHPI-TiO2 complex was preserved by 3 mol% of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) acting as a cooperative catalyst. Moreover, selectivities for the imine products were also promoted by TEMPO. Superoxide anion radical (O2−) were evidenced to be the primary reactive oxygen species (ROS) to execute the oxidative conversions. This work suggests that TiO2 surface complexes can be robust photocatalysts for visible light-driven selective aerobic reactions, provided that an appropriate cooperative redox catalyst exists to channel the photocatalytic electron transfer.

Synthesis and characterisation of [Cu4In(PPh3)3SePh(μ-SePh)3(μ3-SePh)3], and its application as a precursor of a sensitizer for a photocatalyst

An active and robust photocatalyst for water splitting.

A robust photocatalyst of Au25@ZIF-8@TiO2-ReP with dual photoreductive sites to promote photoelectron utilization in H2O splitting to H2 and CO2 reduction to CO.

Sustaining long-term chemical or photochemical stability of a homogeneous molecular catalyst remains a significant challenge. We report a remarkable improvement of the activity and stability of a Au25@ZIF-8@TiO2-ReP catalyst via composition engineering with double redox active sites of Au25 NCs and a Re(i) complex for H2 and CO evolution to promote electron utilization.

Amorphous Carbon Nitride as a Robust Photocatalyst for Biocatalytic Solar-to-Chemical Conversion

In situ regeneration of nicotinamide cofactor (NADH) is imperative because it is required as a reducing power for driving many redox enzymatic cycles useful in industry. Here, we report that amorphous carbon nitride (ACN) is a promising and robust photocatalyst for solar-driven biotransformation via NADH regeneration. Under visible light (λ > 420 nm), NADH regeneration yields by ACN reached 62.3% within an hour, whereas partially crystalline polymeric carbon nitride (CCN) hardly reduced NAD+ to NADH. Subsequently, the regenerated cofactor was consumed by l-glutamate dehydrogenase, a NADH-dependent enzyme, achieving the conversion of α-ketoglutarate with a turnover frequency of 2640 h–1. ACN showed excellent catalytic activity and long-term stability for light-driven biocatalysis; NADH regeneration efficiency after eight cycles remained above 92% of the first cycle’s efficiency, and the enzymatic reaction proceeded for more than 12 h without significant loss of ACN’s photoactivity. The remarkable photocata...

Ferroelectric polarization promoted bulk charge separation for highly efficient CO2 photoreduction of SrBi4Ti4O15

Fast recombination of photogenerated charge carriers in bulk remains the major obstacle for photocatalysis nowadays. Developing ferroelectrics directly as photoactive semiconducting catalysts may be promising in view of the strong ferroelectric polarization that induces the anisotropic charge separation. Here, we report a ferroelectric layered perovskite SrBi4Ti4O15 as a robust photocatalyst for efficient CO2 reduction. In the absence of co-catalysts and sacrificial agents, the annealed SrBi4Ti4O15 nanosheets with the strongest ferroelectricity cast a prominent photocatalytic CO2 reduction activity for CH4 evolution with a rate of 19.8 μmol h−1 g−1 in the gas-solid reaction system, achieving an apparent quantum yield (AQY) of 1.33% at 365 nm, outperforming most of the reported photocatalysts. The ferroelectric hysteresis loop, piezoresponse force microscopy (PFM) and ns-level time-resolved fluorescence spectra uncover that the outstanding CO2 photoreduction activity of SrBi4Ti4O15 mainly stems from the strong ferroelectric spontaneous polarization along [100] direction, which allows efficient bulk charge separation along opposite direction. DFT calculations also disclose that both electrons and holes show the smallest effective masses along a axis, verifying the high mobility of charge carriers facilitated by ferroelectric polarization. This study suggests that the traditionally semiconducting ferroelectric materials that have long been studied as ferro/piezoelectric ceramics now may be powerfully applied in the photocatalytic field to deal with the growing energy crisis.

Open‐mouth spherical g‐C3N4/Fe‐2, 5‐thiophenedicarboxylic acid hybrid photocatalyst for dye degradation and bacterial inactivation

AbstractBACKGROUNDPhoto‐remediation of water is seen as an economical and sustainable solution to undertake the rampant pollution by dyes and bacterial pathogens. Despite significant advances made in semiconductor mediated photocatalysis, the search for cheap, efficient, eco‐friendly and robust photocatalyst has underachieved.RESULTSThis paper reports the use of graphitic carbon nitride (g‐C3N4) supported open‐mouth spherical iron (III) based metal‐organic framework (MOF) hybrid photocatalyst for rapid degradation of acidic dyes and bacterial pathogens. Open‐mouth Fe‐2,5‐thiophenedicarboxylic acid (Fe‐TDA) MOF was prepared by microwave‐heating and coupled with g‐C3N4 using methanol as solvent. Compared with the parent g‐C3N4 and Fe‐TDA, the resultant g‐C3N4/Fe‐TDA(x) hybrids have shown nearly 4‐fold increase in acid violet 7 (AV7) dye degradation and Escherichia coli bacterial growth inhibition. The improvement in photo‐response of g‐C3N4/Fe‐TDA(x) hybrids is ascribed to the exceptional specific surface area of the open‐mouth MOF structure, rapid diffusion, transport of charged species and improved dissociation of photo‐excitons. The present work may offer new directions for the synthesis of g‐C3N4/MOF hybrid photocatalysts for visible light‐driven applications.CONCLUSIONA new open‐mouth nanospherical g‐C3N4/Fe‐TDA2wt% photocatalyst developed by microwave heating, produced a high specific surface area of 114 m2 g−1, and improved rate kinetics of AV 7 dye photodegradation and E. coli inactivation. © 2018 Society of Chemical Industry

Single titanium-oxide species implanted in 2D g-C3N4 matrix as a highly efficient visible-light CO2 reduction photocatalyst

A visible-light-response, efficient and robust photo-catalyst for CO2 reduction is highly desirable. Herein, we demonstrate that single titanium-oxide species implanted in two-dimensional (2D) graphitic carbon nitride (g-C3N4) matrix (2D TiO-CN) can efficiently photo-catalyze the reduction of CO2 to CO under the irradiation of visible light. The synergistic interaction between single titanium oxide species and g-C3N4 in 2D TiO-CN not only enhances the separation of photo-excited charges, but also results in visible light response of single titanium-oxide species, realizing high activity of CO2 photo-reduction with extremely high CO generation rate of 283.9 μmol·h−1·g−1, 5.7, 6.8 and 292.2 times larger than those of TiO2/CN hybrid material, CN and commercial TiO2, respectively. Time-resolved fluorescence and electron spin resonance spectroscopy revealed the catalytic mechanism of the fabricated 2D TiO-CN photocatalysts for CO2 reduction.

Versatile, metal free and temperature-controlled g-C3N4 as a highly efficient and robust photocatalyst for the degradation of organic pollutants

In the present study, we report novel graphitic carbon nitride (g-C3N4) nanosheets at different calcination temperatures viz 500 °C, 550 °C and 600 °C by the simple hydrothermal synthesis for photocatalytic degradation of organic contaminants. The crystal structure, optical properties, and surface morphology were studied by various tools such as X-ray diffraction, UV–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy analysis. The as-synthesized g-C3N4 nanosheets exhibited a hexagonal phase and had good crystallinity with a crystallite size of ~ 68 nm. The photodegradation efficiency of g-C3N4 nanosheets showed excellent photocatalytic activity towards RhB and CV dye solution, and the dye degraded within 70 and 60 min, respectively. The g-C3N4 @550 °C nanosheets showed superior photocatalytic activity due to the adsorption capability and delayed electron hole recombination rate. In addition, the photocatalytic mechanism and reusability test were also found by trapping experiments. The proposed photogenerated electron–hole separation mechanism of the g-C3N4 photocatalyst.

Two-dimensional amorphous NiO as a plasmonic photocatalyst for solar H2 evolution

Amorphous materials are usually evaluated as photocatalytically inactive due to the amorphous nature-induced self-trapping of tail states, in spite of their achievements in electrochemistry. NiO crystals fail to act as an individual reactor for photocatalytic H2 evolution because of the intrinsic hole doping, regardless of their impressive cocatalytic ability for proton/electron transfer. Here we demonstrate that two-dimensional amorphous NiO nanostructure can act as an efficient and robust photocatalyst for solar H2 evolution without any cocatalysts. Further, the antenna effect of surface plasmon resonance can be introduced to construct an incorporate antenna-reactor structure by increasing the electron doping. The solar H2 evolution rate is improved by a factor of 19.4 through the surface plasmon resonance-mediated charge releasing. These findings thus open a door to applications of two-dimensional amorphous NiO as an advanced photocatalyst.

Ultrafine Ag@AgI nanoparticles on cube single-crystal Ag3PO4 (1 0 0): An all-day-active Z-Scheme photocatalyst for environmental purification

Exploring and designing an efficient and robust photocatalyst toward the degradation of organic pollutants under nature sunlight irradiation is a challenging research topic. The ability to maintain the photocatalytic activity in the entire daytime will be the ultimate goal for further widespread application of solar energy-driven semiconductor photocatalysis. Here, an all-day-active Z-scheme photocatalytic system is reported by employing Ag@AgI nanoparticles decorated Ag3PO4 cubes (C-Ag3PO4@Ag@AgI). By coupling the pronounced carrier separation as well as increased stability, the C-Ag3PO4@Ag@AgI is capable of performing efficient Rhodamine B (RhB) and bisphenol A (BPA) degradation under sunlight irradiation, and still persist noticeable activity when the light is very weak. The RhB (20 mg/L, 50 mL) can be completely degraded by C-Ag3PO4@Ag@AgI (30 mg) within 1 h with the average luminous power of 117.5 mW (3.14 cm2). Dramatically, the as-prepared samples can still maintain photocatalytic activity even in a cloudy day (0.2–6.7 mW). This work has offered a valuable concept of continuous pollutant removal under nature sunlight irradiation in the entire daytime, which may serve as a model system for the wide environment applications, such as the removal of low-level pollutants under weak light irradiation.

A facile and green synthesis of CDs-MoS2-Fe3O4 nanohybrid for recyclable and enhanced photocatalysis in dye degradation

Herein, we demonstrate a facile synthesis of CDs-MoS2-Fe3O4 nanohybrid composites as an efficient photocatalyst to enhance the removal of dyes from wastewater. Detailed characterization through SEM, TEM, EDAS, UV-vis, XRD, FT-IR and VSM confirmed the synthesis of thin MoS2 nanosheets and the formation of the nanohybrid composites. As a result, CDs-MoS2-Fe3O4 exhibits excellent reusability through magnetic separation and its degradation rate of methylene blue as high as 96.8% with few additions of materials (25 μg/ml). The ultrahigh photocatalytic performance and chemical stability, accompanied with this facile and simple synthetic process, promising CDs-MoS2-Fe3O4 as a low-cost, ultrahigh-performance and robust photocatalyst in practical dyes degradation.