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MoS <sub/>2</sub> Nanoflowers as a Gateway for Solar-Driven CO <sub/>2</sub> Photoreduction
摘要： The layering of transition metal dichalcogenides (TMD) has revealed unprecedented engineering opportunities for optoelectronics, field emitter and photocatalysis applications. Precise and controlled intrinsic material property combinations is the crucial demand needed for visible light photocatalysis optimization, which we demonstrate in this work with MoS2 nanoflowers containing abundant edge plane flakes for CO2 photoreduction optimization. This is the first time controlled imperfections and flake thickness through facile CVD synthesis was demonstrated on the nanoflowers, revealing the tuning ability of flake edge morphology, nanoflower size, stacked-sheet thickness, optical band gap energy (Eg) and catalytic function. These influences facilitated Eg tuning from 1.38 to 1.83 eV and the manifestation of the 3R phase prompting improvement to the catalytic behavior. The ‘sweet spot’ of higher catalytic activity during photoreduction experiments was found in those with plentiful nanoflower density and thick edge-site abundance. Ample edge-sites with dangling bonds, and crystal impurities assisted in lowering the Eg to achieve reduced recombination for improved photocatalytic reactions, including those found on what would have been a typical chemically inert basal plane. The production rates of CO improved two-fold after a calculated post-treatment reduction step. This reliable CVD technique for nanoflower synthesis paves the way for enhanced understating of synthetic parameters for defect-laden 2D TMD nanoflower structures. We also note that photocatalysis should consider Mars applications, as deep space humans exploration will be require harvesting of the CO2 rich atmosphere to generate fuel from sustainable resources, such as the sun.
关键词： molybdenum disulfide,band gap tuning,visible light catalyst,transition metal dichalcogenide
更新于2025-09-10 09:29:36
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Photochemical generation of radicals from alkyl electrophiles using a nucleophilic organic catalyst
摘要： Chemists extensively use free radical reactivity for applications in organic synthesis, materials science, and life science. Traditionally, generating radicals requires strategies that exploit the bond dissociation energy or the redox properties of the precursors. Here, we disclose a photochemical catalytic approach that harnesses different physical properties of the substrate to form carbon radicals. We use a nucleophilic dithiocarbamate anion catalyst, adorned with a well-tailored chromophoric unit, to activate alkyl electrophiles via an SN2 pathway. The resulting photon-absorbing intermediate affords radicals upon homolytic cleavage induced by visible light. This catalytic SN2-based strategy, which exploits a fundamental mechanistic process of ionic chemistry, grants access to open-shell intermediates from a variety of substrates that would be incompatible with or inert to classical radical-generating strategies. We also describe how the method’s mild reaction conditions and high functional group tolerance could be advantageous for developing C–C bond-forming reactions, for streamlining the preparation of a marketed drug, for the late-stage elaboration of biorelevant compounds and for enantioselective radical catalysis.
关键词： radicals,SN2 pathway,alkyl electrophiles,photochemical,C–C bond-forming reactions,visible light,enantioselective radical catalysis,nucleophilic organic catalyst
更新于2025-09-10 09:29:36
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Synthesis of Reduced Graphene Oxide with Adjustable Microstructure Using Regioselective Reduction in the Melt of Boric Acid: Relationship Between Structural Properties and Electrochemical Performance
摘要： The melt of H3BO3 was used to reach a controllable reduced graphene oxide (rGO) synthesis protocol using a graphene oxide (GO) precursor. Thermogravimetric analysis and differential scanning calorimetry (TG/DSC) investigation and scanning electron microscopy (SEM) images have shown that different from GO powder, reduction of GO in the melt of H3BO3 leads to the formation of less disordered structure of basal graphene planes. Threefold coordinated boron atom acts as a scavenger of oxygen atoms during the process of GO reduction. Fourier-transform infrared (FTIR) spectra of synthesized products have shown that the complex of glycerol and H3BO3 acts as a regioselective catalyst in epoxide ring-opening reaction and suppress the formation of ketone C=O functional groups at vacancy sites. Thermal treatment at 800 ?C leads to the increased concentration of point defects in the backbone structure of rGO. Synthesized materials were tested electrochemically. The electrochemical performance of these materials essentially differs depending on the preparation protocol. The highest charge/discharge rate and double-layer capacitance were found for a sample synthesized in the melt of H3BO3 in the presence of glycerol and treated at 800 ?C. The effect of optimal porosity and high electrical conductivity on the electrochemical performance of prepared materials also were studied.
关键词： oxygen scavenger,boric acid,graphene oxide,adjustable microstructure,regioselective catalyst
更新于2025-09-10 09:29:36
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Photoactive ZnO Materials for Solar Light-Induced CuxO-ZnO Catalyst Preparation
摘要： In this work, the solar light-induced redox photoactivity of ZnO semiconductor material was used to prepare CuxO-ZnO composite catalysts at room temperature with a control of the chemical state of the copper oxide phase. Cu2(I)O-ZnO and Cu(II)O-ZnO composite catalysts were prepared by using Cu(acac)2 in tetrahydrofuran-water and Cu(NO3)2 in water as metallic precursor, respectively. Prior to the implementation of the photon-assisted synthesis method, the most efficient photoactive ZnO material was selected from among different ZnO materials prepared by the low temperature polyol and precipitation methods with carbonates and carbamates as precipitation agents. The photocatalytic degradation of the 4-chlorophenol compound in water under simulated solar light was taken as a model reaction. The ZnO support materials were characterized by X-ray diffraction (XRD), surface area and porosimetry measurements, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the synthesis method strongly influenced their photoactivity in terms of 4-chlorophenol degradation and of total organic carbon removal. The most photoactive ZnO material was prepared by precipitation with carbonates and calcined at 300 ?C, benefiting from a high specific surface area and a small mean crystallite size for achieving a complete 4-chlorophenol mineralization within 70 min of reaction, with minimum Zn2+ released to the solution. Besides thermal catalysis applications, this work has opened a new route for the facile synthesis of Cu2O-ZnO heterojunction photocatalysts that could take place under solar light of the heterojunction built between the p-type semi-conductor Cu2O with direct visible light band gap and the ZnO semiconductor phase.
关键词： ZnO,CuxO-ZnO catalyst,photo-oxidation,4-chlorophenol,photodeposition
更新于2025-09-09 09:28:46
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Catalyst-free synthesis of few-layer graphene films on silicon dioxide/Si substrates using ethylene glycol by chemical vapor deposition
摘要： Catalyst-free growth of graphene directly on dielectric substrates is a challenging work for graphene-based electronics. In this paper, a simple method to synthesize large area few layer graphene films on silicon dioxide/Si substrates by chemical vapor deposition is reported. A novel liquid carbon source (ethylene glycol) is used, without any catalysts. The obtained graphene films are characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy. The field effect transistor with graphene film as channel material is fabricated, and the carrier mobility is 707 cm2/V.S. This work offers a new strategy to directly grow graphene on silicon dioxide/Si substrates, and the as-synthesized graphene films may have potential applications in sensors, conductive films, electronic devices, etc.
关键词： Field effect transistor,Synthesis,Catalyst-free,Graphene,Ethylene glycol
更新于2025-09-09 09:28:46
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Modeling and Optimization of the Photocatalytic Reduction of Molecular Oxygen to Hydrogen Peroxide over Titanium Dioxide
摘要： This study focuses on understanding the mechanisms for optimization of the photocatalytic hydrogen peroxide production over TiO2 (Aeroxide P25). Via precise control of the reaction parameters (pH, temperature, catalyst amount, oxygen content, sacrificial electron donor and light intensity) it is possible to tune either the apparent quantum yield or the production rate. As a result of the optimization, apparent quantum yields of up to 19.8 % and production rates of up to 83 μM min-1 were obtained. We also observed a light dependent change of the reaction order and an interdependency of the light intensity and catalyst amount and developed a well-fitting kinetic model for it, which might also be applied to other reactions. Furthermore, a previously unreported inactivation of the photocatalyst in case of water oxidation is described.
关键词： titanium dioxide (TiO2),hydrogen peroxide (H2O2),oxygen reduction,catalyst inactivation,light intensity,photocatalysis
更新于2025-09-09 09:28:46
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Green Energy based Thermochemical and Photochemical Hydrogen Production
摘要： A significant amount of hydrogen is required to satisfy the hydroprocessing needs of petroleum refinery, natural gas cleaning, and biofuel upgrading. Meanwhile, hydrogen is a very promising candidate of energy due to its high energy output per mass unit as compared to other sources of energy. In this article, the production of hydrogen is overviewed from the traditional technology as the thermochemical processes of fossil fuels to the current development in photoelectrochemical processes or even hybrid technologies. The catalysts for methane reforming and visible-light absorption were summarized. Both processes employ oxides as the catalyst. Because catalytic oxides are mostly lack of visible-light absorption function, the visible-light absorption properties could be rendered by doping these oxides with metal, nitrogen, or even sulfur. Further complete substitution of the oxygen atoms leads to non-oxide catalyst. Moreover, multidimensional photochemical catalysts have acquired more attention over traditional powered catalysts. Finally, a vision is exhibited for the efficiency and the future trends on production of H2.
关键词： Tri-reforming,catalyst,Biomass,Electrolysis,Dry Reforming,Hydrogen Production,Steam Reforming,Methane,Autothermal Reforming,Solar energy,Gasification,Coal
更新于2025-09-09 09:28:46
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The effect of growth condition on graphene growth via Cu-assisted plasma reduction and restoration of graphene oxide
摘要： Graphene, a monolayer sheet of graphite, shows plenty of attractive properties and has been expected to replace conventional materials in various fields. For the industrial application of graphene, a high throughput synthesis method on arbitrary substrates is strongly required. Chemical exfoliation via graphene oxide (GO) is thought to be a suitable method for the high throughput synthesis. However, the crystallinity of reduced GO is unacceptably low. Although we found that the plasma treatment with Cu catalyst yields graphene with high crystallinity from GO on a dielectric substrate, the effect of the growth parameter has been unclear. Here, we investigated the effect of the gas ratio of CH4 and H2 in this process on the crystallinity of graphene. By optimizing the gas ratio, we succeeded in reducing and restoring GO to the extent that its mobility increased to 9.0 × 102 cm2 V?1 s?1.
关键词： graphene oxide,plasma reduction,graphene,crystallinity,Cu catalyst
更新于2025-09-09 09:28:46
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Molecular structure of PANI and its homologue PANI–PEO2000 catalyzed by Maghnite-H+ (Algerian MMT): synthesis, characterization and physical and chemical properties
摘要： The homopolymer (PANI) and its homologue PANI–PEO2000 copolymer have been prepared under effect of Maghnite-H+ (Algerian MMT) in different weight percentages (wt%) by cationic polymerization method. The formation of the hydrogen bonding between PANI and PEO2000 and structure of PANI are predicted by the FT-IR and 1HNMR spectra. Glass transition temperature of pure PANI and pure PEO2000 are, respectively, Tg = 74 °C and Tg = 65 °C, but DSC analysis for the copolymer (PANI–PEO2000) showed only one (Tg = 16.79 °C) implying compatibility of PANI and PEO2000. Here we can suggest that under suitable condition (the amount of catalyst, molecular weight and functionality of the reactive stabilizer (PEO2000) and molar ratio of (PANI/PEO2000), our catalyst can improve the morphology, structure and chemical properties of PANI and its homologue PANI–PEO2000.
关键词： Maghnite-H+,1HNMR spectroscopy,DSC,PEO,GPC,Conducting polymer,Green catalyst,Polyaniline
更新于2025-09-09 09:28:46
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Observed Dramatically Improved Catalysis of Ag Shell on Au/Ag Core-Shell Nanorods is Due to Silver Impurities Released During Etching Process
摘要： Core/shell bimetallic nanoparticles are highly popular in electrocatalysis; it is argued that the core metal enhances the catalytic properties of the shell. We have investigated the electrocatalytic properties of Au/Ag core-shell nanorods (Au/Ag NRs) where Ag shell was thinned by aging in the presence of cetyltrimethylammonium bromide. We observed excellent electrocatalysis toward hydrogen peroxide electroreduction upon decreasing the Ag shell thickness, which would, at first, appear to imply a strong synergistic effect of the Au core with the Ag shell for electrocatalysis. We show, however, that this electrocatalysis is not caused by particular Au/Ag core/shell structures but rather by the presence of residual silver impurities in the form of Ag nanoparticles (Ag NPs) formed during the preparation of the thin-layer silver shell/gold core nanorods.
关键词： bimetallic particles,Au/Ag nanorods,varied shell thickness,physicochemical transformation,hydrogen peroxide catalyst
更新于2025-09-04 15:30:14