Open AccessEditorial
Reflections on Catalytic Selective Oxidation: Opportunities and Challenges
Catalysts 2017, 7(1), 34; doi:10.3390/catal7010034 (registering DOI) -
Abstract Currently, and looking forward, there is an ever increasing demand to perform chemical transformations with optimized atom and energy efficiency [...] Full article
Open AccessArticle
Synergically Improving Light Harvesting and Charge Transportation of TiO2 Nanobelts by Deposition of MoS2 for Enhanced Photocatalytic Removal of Cr(VI)
Catalysts 2017, 7(1), 30; doi:10.3390/catal7010030 -
Abstract
Herein, MoS2/TiO2 nanobelts heterojunction have been successfully synthesized by in situ growth method for photocatalytic reduction of Cr(VI). TiO2 nanobelts (NBs) with rough surface were prepared firstly by acidic treatment process, which is beneficial for deposition and growth of
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Herein, MoS2/TiO2 nanobelts heterojunction have been successfully synthesized by in situ growth method for photocatalytic reduction of Cr(VI). TiO2 nanobelts (NBs) with rough surface were prepared firstly by acidic treatment process, which is beneficial for deposition and growth of MoS2 to form heterojunctions. As a result of special energy level offset and nanostructure, MoS2/TiO2 NBs composite were endowed with higher light-harvesting capacity and charge transportation efficiency, which are indispensible merits for excellent photocatalytic activity. The photocatalytic reduction of Cr(VI) reveals that the synthesized MoS2/TiO2 NBs composite have superior photocatalytic ability than other samples. Meanwhile, a photoreduction mechanism is proposed based on the systematic investigation, where the photogenerated electrons are demonstrated as the dominant reductive species to reduce Cr(VI) to Cr(III). Full article
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Open AccessReview
Nanostructured Inorganic Materials at Work in Electrochemical Sensing and Biofuel Cells
Catalysts 2017, 7(1), 31; doi:10.3390/catal7010031 -
Abstract
The future of analytical devices, namely (bio)sensors, which are currently impacting our everyday life, relies on several metrics such as low cost, high sensitivity, good selectivity, rapid response, real-time monitoring, high-throughput, easy-to-make and easy-to-handle properties. Fortunately, they can be readily fulfilled by electrochemical
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The future of analytical devices, namely (bio)sensors, which are currently impacting our everyday life, relies on several metrics such as low cost, high sensitivity, good selectivity, rapid response, real-time monitoring, high-throughput, easy-to-make and easy-to-handle properties. Fortunately, they can be readily fulfilled by electrochemical methods. For decades, electrochemical sensors and biofuel cells operating in physiological conditions have concerned biomolecular science where enzymes act as biocatalysts. However, immobilizing them on a conducting substrate is tedious and the resulting bioelectrodes suffer from stability. In this contribution, we provide a comprehensive, authoritative, critical, and readable review of general interest that surveys interdisciplinary research involving materials science and (bio)electrocatalysis. Specifically, it recounts recent developments focused on the introduction of nanostructured metallic and carbon-based materials as robust “abiotic catalysts” or scaffolds in bioelectrochemistry to boost and increase the current and readout signals as well as the lifetime. Compared to biocatalysts, abiotic catalysts are in a better position to efficiently cope with fluctuations of temperature and pH since they possess high intrinsic thermal stability, exceptional chemical resistance and long-term stability, already highlighted in classical electrocatalysis. We also diagnosed their intrinsic bottlenecks and highlighted opportunities of unifying the materials science and bioelectrochemistry fields to design hybrid platforms with improved performance. Full article
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Open AccessReview
A Short Review on the Catalytic Activity of Hydrotalcite-Derived Materials for Dry Reforming of Methane
Catalysts 2017, 7(1), 32; doi:10.3390/catal7010032 -
Abstract
Nickel-containing hydrotalcite-derived materials have been recently proposed as promising materials for methane dry reforming (DRM). Based on a literature review and on the experience of the authors, this review focuses on presenting past and recent achievements on increasing activity and stability of hydrotalcite-based
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Nickel-containing hydrotalcite-derived materials have been recently proposed as promising materials for methane dry reforming (DRM). Based on a literature review and on the experience of the authors, this review focuses on presenting past and recent achievements on increasing activity and stability of hydrotalcite-based materials for DRM. The use of different NiMgAl and NiAl hydrotalcite (HT) precursors, various methods for nickel introduction into HT structure, calcination conditions and promoters are discussed. HT-derived materials containing nickel generally exhibit high activity in DRM; however, the problem of preventing catalyst deactivation by coking, especially below 700 °C, is still an open question. The proposed solutions in the literature include: catalyst regeneration either in oxygen atmosphere or via hydrogasification; or application of various promoters, such as Zr, Ce or La, which was proven to enhance catalytic stability. Full article
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Open AccessArticle
Mild and Highly Efficient Copper(I) Inspired Acylation of Alcohols and Polyols
Catalysts 2017, 7(1), 33; doi:10.3390/catal7010033 -
Abstract
A new and highly efficient method mediated by tetrakis(acetonitrile)copper(I) triflate for activating both simple and highly hindered anhydrides in the acylation of alcohols and polyols is described. This new acylation method is mild and mostly proceeds at room temperature with low catalyst loading.
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A new and highly efficient method mediated by tetrakis(acetonitrile)copper(I) triflate for activating both simple and highly hindered anhydrides in the acylation of alcohols and polyols is described. This new acylation method is mild and mostly proceeds at room temperature with low catalyst loading. The method is versatile and has been extended to a wide variety of different alcohol substrates to afford the corresponding ester products in good to excellent yields. Full article
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Open AccessArticle
Visualization of Gas Distribution in a Model AP-XPS Reactor by PLIF: CO Oxidation over a Pd(100) Catalyst
Catalysts 2017, 7(1), 29; doi:10.3390/catal7010029 -
Abstract
In situ knowledge of the gas phase around a catalyst is essential to make an accurate correlation between the catalytic activity and surface structure in operando studies. Although ambient pressure X-ray photoelectron spectroscopy (AP-XPS) can provide information on the gas phase as well
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In situ knowledge of the gas phase around a catalyst is essential to make an accurate correlation between the catalytic activity and surface structure in operando studies. Although ambient pressure X-ray photoelectron spectroscopy (AP-XPS) can provide information on the gas phase as well as the surface structure of a working catalyst, the gas phase detected has not been spatially resolved to date, thus possibly making it ambiguous to interpret the AP-XPS spectra. In this work, planar laser-induced fluorescence (PLIF) is used to visualize the CO2 distribution in a model AP-XPS reactor, during CO oxidation over a Pd(100) catalyst. The results show that the gas composition in the vicinity of the sample measured by PLIF is significantly different from that measured by a conventional mass spectrometer connected to a nozzle positioned just above the sample. In addition, the gas distribution above the catalytic sample has a strong dependence on the gas flow and total chamber pressure. The technique presented has the potential to increase our knowledge of the gas phase in AP-XPS, as well as to optimize the design and operating conditions of in situ AP-XPS reactors for catalysis studies. Full article
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Open AccessFeature PaperArticle
The Effect of Sr Addition in Cu- and Fe-Modified CeO2 and ZrO2 Soot Combustion Catalysts
Catalysts 2017, 7(1), 28; doi:10.3390/catal7010028 -
Abstract
This study investigates the activity of transition and alkaline-earth metal-doped catalysts supported on ceria or zirconia for the NOx-assisted oxidation of diesel particulate. A series of Cu- and Fe-impregnated catalysts over CeO2 and ZrO2 supports were prepared by incipient
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This study investigates the activity of transition and alkaline-earth metal-doped catalysts supported on ceria or zirconia for the NOx-assisted oxidation of diesel particulate. A series of Cu- and Fe-impregnated catalysts over CeO2 and ZrO2 supports were prepared by incipient wetness impregnation and characterized by BET, X-ray diffraction (XRD), and temperature-programmed reduction (TPR) experiments while their catalytic activity was investigated in NOx-assisted reaction by means of temperature programmed oxidation experiments (TPO). Higher activity was achieved by copper modified catalysts; the addition of Sr positively affected the performance of the materials, suggesting a synergic effect between transition metals and alkaline-earth metal. The role of copper is correlated to the oxidation of NO to NO2, while strontium seems to be mainly involved in the storage of NOx species. Full article
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Open AccessArticle
Response Surface Methodology and Aspen Plus Integration for the Simulation of the Catalytic Steam Reforming of Ethanol
Catalysts 2017, 7(1), 15; doi:10.3390/catal7010015 -
Abstract
The steam reforming of ethanol (SRE) on a bimetallic RhPt/CeO2 catalyst was evaluated by the integration of Response Surface Methodology (RSM) and Aspen Plus (version 9.0, Aspen Tech, Burlington, MA, USA, 2016). First, the effect of the Rh–Pt weight ratio (1:0, 3:1,
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The steam reforming of ethanol (SRE) on a bimetallic RhPt/CeO2 catalyst was evaluated by the integration of Response Surface Methodology (RSM) and Aspen Plus (version 9.0, Aspen Tech, Burlington, MA, USA, 2016). First, the effect of the Rh–Pt weight ratio (1:0, 3:1, 1:1, 1:3, and 0:1) on the performance of SRE on RhPt/CeO2 was assessed between 400 to 700 °C with a stoichiometric steam/ethanol molar ratio of 3. RSM enabled modeling of the system and identification of a maximum of 4.2 mol H2/mol EtOH (700 °C) with the Rh0.4Pt0.4/CeO2 catalyst. The mathematical models were integrated into Aspen Plus through Excel in order to simulate a process involving SRE, H2 purification, and electricity production in a fuel cell (FC). An energy sensitivity analysis of the process was performed in Aspen Plus, and the information obtained was used to generate new response surfaces. The response surfaces demonstrated that an increase in H2 production requires more energy consumption in the steam reforming of ethanol. However, increasing H2 production rebounds in more energy production in the fuel cell, which increases the overall efficiency of the system. The minimum H2 yield needed to make the system energetically sustainable was identified as 1.2 mol H2/mol EtOH. According to the results of the integration of RSM models into Aspen Plus, the system using Rh0.4Pt0.4/CeO2 can produce a maximum net energy of 742 kJ/mol H2, of which 40% could be converted into electricity in the FC (297 kJ/mol H2 produced). The remaining energy can be recovered as heat. Full article
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Open AccessArticle
Chitosan–Collagen Coated Magnetic Nanoparticles for Lipase Immobilization—New Type of “Enzyme Friendly” Polymer Shell Crosslinking with Squaric Acid
Catalysts 2017, 7(1), 26; doi:10.3390/catal7010026 -
Abstract
This article presents a novel route for crosslinking a polysaccharide and polysaccharide/protein shell coated on magnetic nanoparticles (MNPs) surface via condensation reaction with squaric acid (SqA). The syntheses of four new types of collagen-, chitosan-, and chitosan–collagen coated magnetic nanoparticles as supports for
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This article presents a novel route for crosslinking a polysaccharide and polysaccharide/protein shell coated on magnetic nanoparticles (MNPs) surface via condensation reaction with squaric acid (SqA). The syntheses of four new types of collagen-, chitosan-, and chitosan–collagen coated magnetic nanoparticles as supports for enzyme immobilization have been done. Structure and morphology of prepared new materials were characterized by attenuated total reflectance Fourier-transform infrared (ATR-FTIR), XRD, and TEM analysis. Next, the immobilization of lipase from Candida rugosa was performed on the nanoparticles surface via N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC)/N-hydroxy-succinimide (NHS) mechanism. The best results of lipase activity recovery and specific activities were observed for nanoparticles with polymer shell crosslinked via a novel procedure with squaric acid. The specific activity for lipase immobilized on materials crosslinked with SqA (52 U/mg lipase) was about 2-fold higher than for enzyme immobilized on MNPs with glutaraldehyde addition (26 U/mg lipase). Moreover, a little hyperactivation of lipase immobilized on nanoparticles with SqA was observed (104% and 112%). Full article
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Open AccessCommunication
Aziridine- and Azetidine-Pd Catalytic Combinations. Synthesis and Evaluation of the Ligand Ring Size Impact on Suzuki-Miyaura Reaction Issues
Catalysts 2017, 7(1), 27; doi:10.3390/catal7010027 -
Abstract
The synthesis of new vicinal diamines based on aziridine and azetidine cores as well as the comparison of their catalytic activities as ligand in the Suzuki-Miyaura coupling reaction are described in this communication. The synthesis of three- and four-membered ring heterocycles substituted by
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The synthesis of new vicinal diamines based on aziridine and azetidine cores as well as the comparison of their catalytic activities as ligand in the Suzuki-Miyaura coupling reaction are described in this communication. The synthesis of three- and four-membered ring heterocycles substituted by a methylamine pendant arm is detailed from the parent nitrile derivatives. Complexation to palladium under various conditions has been examined affording vicinal diamines or amine-imidate complexes. The efficiency of four new catalytic systems is compared in the preparation of variously substituted biaryls. Aziridine- and azetidine-based catalytic systems allowed Suzuki-Miyaura reactions from aryl halides including chlorides with catalytic loadings until 0.001% at temperatures ranging from 100 °C to r.t. The evolution of the Pd-metallacycle ring strain moving from azetidine to aziridine in combination with a methylamine or an imidate pendant arm impacted the Suzuki-Miyaura reaction issue. Full article
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Open AccessArticle
Cobalt-Doped Carbon Gels as Electro-Catalysts for the Reduction of CO2 to Hydrocarbons
Catalysts 2017, 7(1), 25; doi:10.3390/catal7010025 -
Abstract
Two original series of carbon gels doped with different cobalt loadings and well-developed mesoporosity, aerogels and xerogels, have been prepared, exhaustively characterized, and tested as cathodes for the electro-catalytic reduction of CO2 to hydrocarbons at atmospheric pressure. Commercial cobalt and graphite sheets
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Two original series of carbon gels doped with different cobalt loadings and well-developed mesoporosity, aerogels and xerogels, have been prepared, exhaustively characterized, and tested as cathodes for the electro-catalytic reduction of CO2 to hydrocarbons at atmospheric pressure. Commercial cobalt and graphite sheets have also been tested as cathodes for comparison. All of the doped carbon gels catalyzed the formation of hydrocarbons, at least from type C1 to C4. The catalytic activity depends mainly on the metal loading, nevertheless, the adsorption of a part of the products in the porous structure of the carbon gel cannot be ruled out. Apparent faradaic efficiencies calculated with these developed materials were better that those obtained with a commercial cobalt sheet as a cathode, especially considering the much lower amount of cobalt contained in the Co-doped carbon gels. The cobalt-carbon phases formed in these types of doped carbon gels improve the selectivity to C3-C4 hydrocarbons formation, obtaining even more C3 hydrocarbons than CH4 in some cases. Full article
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Open AccessArticle
Catalytic Ammonia Decomposition over High-Performance Ru/Graphene Nanocomposites for Efficient COx-Free Hydrogen Production
Catalysts 2017, 7(1), 23; doi:10.3390/catal7010023 -
Abstract
Highly-dispersed Ru nanoparticles were grown on graphene nanosheets by simultaneously reducing graphene oxide and Ru ions using ethylene glycol (EG), and the resultant Ru/graphene nanocomposites were applied as a catalyst to ammonia decomposition for COx-free hydrogen production. Tuning the microstructures of
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Highly-dispersed Ru nanoparticles were grown on graphene nanosheets by simultaneously reducing graphene oxide and Ru ions using ethylene glycol (EG), and the resultant Ru/graphene nanocomposites were applied as a catalyst to ammonia decomposition for COx-free hydrogen production. Tuning the microstructures of Ru/graphene nanocomposites was easily accomplished in terms of Ru particle size, morphology, and loading by adjusting the preparation conditions. This was the key to excellent catalytic activity, because ammonia decomposition over Ru catalysts is structure-sensitive. Our results demonstrated that Ru/graphene prepared using water as a co-solvent greatly enhanced the catalytic performance for ammonia decomposition, due to the significantly improved nano architectures of the composites. The long-term stability of Ru/graphene catalysts was evaluated for COx-free hydrogen production from ammonia at high temperatures, and the structural evolution of the catalysts was investigated during the catalytic reactions. Although there were no obvious changes in the catalytic activities at 450 °C over a duration of 80 h, an aggregation of the Ru nanoparticles was still observed in the nanocomposites, which was ascribed mainly to a sintering effect. However, the performance of the Ru/graphene catalyst was decreased gradually at 500 °C within 20 h, which was ascribed mainly to both the effect of the methanation of the graphene nanosheet under a H2 atmosphere and to enhanced sintering under high temperatures. Full article
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Open AccessEditorial
Acknowledgement to Reviewers of Catalysts in 2016
Catalysts 2017, 7(1), 24; doi:10.3390/catal7010024 -
Abstract The editors of Catalysts would like to express their sincere gratitude to the following reviewers  for assessing manuscripts in 2016.[...] Full article
Open AccessArticle
Synthesis and Application of Novel Ruthenium Catalysts for High Temperature Alkene Metathesis
Catalysts 2017, 7(1), 22; doi:10.3390/catal7010022 -
Abstract
Four pyridinyl alcohols and the corresponding hemilabile pyridinyl alcoholato ruthenium carbene complexes of the Grubbs second generation-type RuCl(H2IMes)(O^N)(=CHPh), where O^N = 1-(2′-pyridinyl)-1,1-diphenyl methanolato, 1-(2′-pyridinyl)-1-(2′-chlorophenyl),1-phenyl methanolato, 1-(2′-pyridinyl)-1-(4′-chlorophenyl),1-phenyl methanolato and 1-(2′-pyridinyl)-1-(2′-methoxyphenyl),1-phenyl methanolato, are synthesized in very good yields. At high temperatures, the precatalysts
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Four pyridinyl alcohols and the corresponding hemilabile pyridinyl alcoholato ruthenium carbene complexes of the Grubbs second generation-type RuCl(H2IMes)(O^N)(=CHPh), where O^N = 1-(2′-pyridinyl)-1,1-diphenyl methanolato, 1-(2′-pyridinyl)-1-(2′-chlorophenyl),1-phenyl methanolato, 1-(2′-pyridinyl)-1-(4′-chlorophenyl),1-phenyl methanolato and 1-(2′-pyridinyl)-1-(2′-methoxyphenyl),1-phenyl methanolato, are synthesized in very good yields. At high temperatures, the precatalysts showed high stability, selectivity and activity in 1-octene metathesis compared to the Grubbs first and second generation precatalysts. The 2-/4-chloro- and 4-methoxy-substituted pyridinyl alcoholato ligand-containing ruthenium precatalysts showed high performance in the 1-octene metathesis reaction in the range 80–110 °C. The hemilabile 4-methoxy-substituted pyridinyl alcoholato ligand improved the catalyst stability, activity and selectivity for 1-octene metathesis significantly at 110 °C. Full article
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Open AccessArticle
Hydrochlorination of Acetylene Catalyzed by an Activated Carbon-Supported Ammonium Hexachlororuthenate Complex
Catalysts 2017, 7(1), 17; doi:10.3390/catal7010017 -
Abstract
Ammonium hexachlororuthenate ((NH4)2RuCl6) complex was used as a catalyst precursor and coconut activated carbon (AC) was used as the support in the preparation process of the Ru-based catalyst. (NH4)2RuCl6/AC catalyst was
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Ammonium hexachlororuthenate ((NH4)2RuCl6) complex was used as a catalyst precursor and coconut activated carbon (AC) was used as the support in the preparation process of the Ru-based catalyst. (NH4)2RuCl6/AC catalyst was prepared via an incipient wetness impregnation method and assessed in an acetylene hydrochlorination reaction. Meanwhile, the (NH4)2RuCl6/AC catalyst was analyzed with low-temperature N2 adsorption/desorption, thermogravimetry (TG), transmission electron microscopy (TEM), temperature programmed reduction (TPR), X-ray photoelectron spectra (XPS), and temperature programmed desorption (TPD) techniques. Catalytic performance test results show that the (NH4)2RuCl6/AC catalyst exhibits a superior catalytic activity with the highest acetylene conversion of 90.5% under the conditions of 170 °C and an acetylene gas hourly space velocity of 180 h−1. The characterization results illustrate that the presence of the NH4+ cation can inhibit coke deposition as well as the agglomeration of ruthenium particles, and it can also enhance the adsorption ability for reactant HCl, hence improving the catalytic activity and stability. Full article
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Open AccessArticle
Core-Shell Structured Ni@SiO2 Catalysts Exhibiting Excellent Catalytic Performance for Syngas Methanation Reactions
Catalysts 2017, 7(1), 21; doi:10.3390/catal7010021 -
Abstract
In this study, we prepared core-shell structured Ni@SiO2 catalysts using chemical precipitation and modified Stöber methods. The obtained Ni@SiO2 samples exhibited excellent catalysis performances, including high CO conversion of 99.0% and CH4 yield of 89.8%. Moreover, Ni@SiO2 exhibited excellent
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In this study, we prepared core-shell structured Ni@SiO2 catalysts using chemical precipitation and modified Stöber methods. The obtained Ni@SiO2 samples exhibited excellent catalysis performances, including high CO conversion of 99.0% and CH4 yield of 89.8%. Moreover, Ni@SiO2 exhibited excellent catalytic stability during a 100 h lifetime test, which was superior to that of the Ni/SiO2 catalyst. The prepared samples were characterized using a series of techniques, and the results indicated that the catalytic performance for syngas methanation reaction of the Ni@SiO2 sample was markedly improved owing to its nanoreactor structure. The strong interaction between the Ni core and the SiO2 shell effectively restrained the growth of particles, and the deposition of C species. Full article
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Open AccessArticle
Plant Extract Mediated Eco-Friendly Synthesis of Pd@Graphene Nanocatalyst: An Efficient and Reusable Catalyst for the Suzuki-Miyaura Coupling
Catalysts 2017, 7(1), 20; doi:10.3390/catal7010020 -
Abstract
Suzuki-Miyaura coupling reaction catalyzed by the palladium (Pd)-based nanomaterials is one of the most versatile methods for the preparation of biaryls. However, use of organic solvents as reaction medium causes a big threat to environment due to the generation of toxic byproducts as
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Suzuki-Miyaura coupling reaction catalyzed by the palladium (Pd)-based nanomaterials is one of the most versatile methods for the preparation of biaryls. However, use of organic solvents as reaction medium causes a big threat to environment due to the generation of toxic byproducts as waste during the work up of these reactions. Therefore, the use of water as reaction media has attracted tremendous attention due to its environmental, economic, and safety benefits. In this study, we report on the synthesis of green Pd@graphene nanocatalyst based on an in situ functionalization approach which exhibited excellent catalytic activity towards the Suzuki–Miyaura cross-coupling reactions of phenyl halides with phenyl boronic acids under facile conditions in water. The green and environmentally friendly synthesis of Pd@graphene nanocatalyst (PG-HRG-Pd) is carried out by simultaneous reduction of graphene oxide (GRO) and PdCl2 using Pulicaria glutinosa extract (PGE) as reducing and stabilizing agent. The phytomolecules present in the plant extract (PE) not only facilitated the reduction of PdCl2, but also helped to stabilize the surface of PG-HRG-Pd nanocatalyst, which significantly enhanced the dispersibility of nanocatalyst in water. The identification of PG-HRG-Pd was established by various spectroscopic and microscopic techniques, including, high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy. The as-prepared PG-HRG-Pd nanocatalyst demonstrated excellent catalytic activity towards the Suzuki-Miyaura cross coupling reactions under aqueous, ligand free, and aerobic conditions. Apart from this the reusability of the catalyst was also evaluated and the catalyst yielded excellent results upon reuse for several times with marginal loss of its catalytic performance. Therefore, the method developed for the green synthesis of PG-HRG-Pd nanocatalyst and the eco-friendly protocol used for the Suzuki coupling offers a mild and effective substitute to the existing protocols and may significantly contribute to the endeavors of green chemistry. Full article
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Open AccessArticle
Facile Sonication Synthesis of WS2 Quantum Dots for Photoelectrochemical Performance
Catalysts 2017, 7(1), 18; doi:10.3390/catal7010018 -
Abstract
Two-dimensional transition metal dichalcogenides, such as tungsten disulfide (WS2), have been actively studied as suitable candidates for photocatalysts due to their unique structural and electronic properties. The presence of active sites at the edges and the higher specific surface area of
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Two-dimensional transition metal dichalcogenides, such as tungsten disulfide (WS2), have been actively studied as suitable candidates for photocatalysts due to their unique structural and electronic properties. The presence of active sites at the edges and the higher specific surface area of these materials are crucial to the photocatalytic activity of the hydrogen evolution reaction. Here, WS2 quantum dots (QDs) have been successfully synthesized by using a combination of grinding and sonication techniques. The morphology of the QDs was observed, using transmission electron microscopy and an atomic force microscope, to have uniform sizes of less than 5 nm. Photoelectrochemical (PEC) measurements show that the current density of WS2 QDs under illumination is almost two times higher than that of pristine WS2. Furthermore, these high-quality WS2 QDs may have various applications in optoelectronics, solar cells, and biomedicine. Full article
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Open AccessArticle
Core-Shell MnO2-SiO2 Nanorods for Catalyzing the Removal of Dyes from Water
Catalysts 2017, 7(1), 19; doi:10.3390/catal7010019 -
Abstract
This work presented a novel core-shell MnO2@m-SiO2 for catalyzing the removal of dyes from wastewater. MnO2 nanorods were sequentially coated with polydopamine (PDA) and polyethyleneimine (PEI) forming MnO2@PDA-PEI. By taking advantage of the positively charged amine groups,
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This work presented a novel core-shell MnO2@m-SiO2 for catalyzing the removal of dyes from wastewater. MnO2 nanorods were sequentially coated with polydopamine (PDA) and polyethyleneimine (PEI) forming MnO2@PDA-PEI. By taking advantage of the positively charged amine groups, MnO2@PDA-PEI was further silicificated, forming MnO2@PDA-PEI-SiO2. After calcination, the composite MnO2@m-SiO2 was finally obtained. MnO2 nanorod is the core and mesoporous SiO2 (m-SiO2) is the shell. MnO2@m-SiO2 has been used to degrade a model dye Rhodamine B (RhB). The shell m-SiO2 functioned to adsorb/enrich and transfer RhB, and the core MnO2 nanorods oxidized RhB. Thus, MnO2@m-SiO2 combines multiple functions together. Experimental results demonstrated that MnO2@m-SiO2 exhibited a much higher efficiency for degradation of RhB than MnO2. The RhB decoloration and degradation efficiencies were 98.7% and 84.9%, respectively. Consecutive use of MnO2@m-SiO2 has demonstrated that MnO2@m-SiO2 can be used to catalyze multiple cycles of RhB degradation. After six cycles of reuse of MnO2@m-SiO2, the RhB decoloration and degradation efficiencies were 98.2% and 71.1%, respectively. Full article
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Open AccessFeature PaperReview
Catalyst, Membrane, Free Electrolyte Challenges, and Pathways to Resolutions in High Temperature Polymer Electrolyte Membrane Fuel Cells
Catalysts 2017, 7(1), 16; doi:10.3390/catal7010016 -
Abstract
High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are being studied due to a number of benefits offered versus their low temperature counterparts, including co-generation of heat and power, high tolerance to fuel impurities, and simpler system design. Approximately 90% of the literature
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High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are being studied due to a number of benefits offered versus their low temperature counterparts, including co-generation of heat and power, high tolerance to fuel impurities, and simpler system design. Approximately 90% of the literature on HT-PEM is related to the electrolyte and, for the most part, these electrolytes all use free phosphoric acid, or similar free acid, as the ion conductor. A major issue with using phosphoric acid based electrolytes is the free acid in the electrodes. The presence of the acid on the catalyst sites leads to poor oxygen activity, low solubility/diffusion, and can block electrochemical sites through phosphate adsorption. This review will focus on these issues and the steps that have been taken to alleviate these obstacles. The intention is this review may then serve as a tool for finding a solution path in the community. Full article
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