scholarly journals Amorphous MoSxOy/h-BNxOy Nanohybrids: Synthesis and Dye Photodegradation

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3232
Author(s):  
Andrei T. Matveev ◽  
Anton S. Konopatsky ◽  
Denis V. Leybo ◽  
Ilia N. Volkov ◽  
Andrey M. Kovalskii ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Density Functional ◽  
Dft Method ◽  
Chain Structure ◽  
Molybdenum Sulfide ◽  
Structural Defects ◽  
Partial Substitution ◽  
Hydrogen Electrode ◽  
X Ray

Molybdenum sulfide is a very promising catalyst for the photodegradation of organic pollutants in water. Its photocatalytic activity arises from unsaturated sulfur bonds, and it increases with the introduction of structural defects and/or oxygen substitutions. Amorphous molybdenum sulfide (a-MoSxOy) with oxygen substitutions has many active sites, which create favorable conditions for enhanced catalytic activity. Here we present a new approach to the synthesis of a-MoSxOy and demonstrate its high activity in the photodegradation of the dye methylene blue (MB). The MoSxOy was deposited on hexagonal boron oxynitride (h-BNO) nanoflakes by reacting h-BNO, MoCl5, and H2S in dimethylformamide (DMF) at 250 °C. Both X-ray diffraction analysis and high-resolution TEM show the absence of crystalline order in a-MoSxOy. Based on the results of Raman and X-ray photoelectron spectroscopy, as well as analysis by the density functional theory (DFT) method, a chain structure of a-MoSxOy was proposed, consisting of MoS3 clusters with partial substitution of sulfur by oxygen. When a third of the sulfur atoms are replaced with oxygen, the band gap of a-MoSxOy is approximately 1.36 eV, and the valence and conduction bands are 0.74 eV and −0.62 eV, respectively (relative to a standard hydrogen electrode), which satisfies the conditions of photoinduced splitting of water. When illuminated with a mercury lamp, a-MoSxOy/h-BNxOy nanohybrids have a specific mass activity in MB photodegradation of approximately 5.51 mmol g−1 h−1, which is at least four times higher than so far reported values for nonmetal catalysts. The photocatalyst has been shown to be very stable and can be reused.

scholarly journals Gram-Scale Synthesis of Pt-Cu Nanowires with Enhanced Electrocatalytic Activity towards Methanol Oxidation Reaction

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Ning Sui ◽  
Hongxu Gao ◽  
Yukai Wang ◽  
Jiali Li ◽  
Shiyu Qu ◽  
...  
Keyword(s):  
Methanol Oxidation ◽  
Photoelectron Spectroscopy ◽  
Electrocatalytic Activity ◽  
Inductively Coupled Plasma ◽  
Active Sites ◽  
Structural Defects ◽  
Methanol Oxidation Reaction ◽  
X Ray ◽  
Cu Nanowires ◽  
Inductively Coupled

A facile method to prepare Pt-Cu nanowires (NWs) was introduced. Structural characterization such as high-resolution transmission electron microscope (HR-TEM), selected-area electron diffraction (SAED), EDS element mapping, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and inductively coupled plasma mass spectrometry (ICP-MS) showed the formation of Pt-Cu alloy, with a width of 4.5 nm on average. The formation process of Pt-Cu NWs was studied; it was found that bromine ion, who has preferential adsorption on Pt (100) face, served as a growth-directing agent; Brij58 not only served as a protector but also played an important role in forming Pt-Cu NWs; the mechanism was proposed. Their electrocatalytic activity towards methanol oxidation was investigated; we found that the current density of Pt-Cu NWs was 295 mA·mg-1 when the ratio of Pt/Cu is 1 : 1, which is 11.5 and 2.35 times higher than that of pure Pt (26 mA·mg-1) and commercial Pt/C (126 mA·mg-1). The high electrocatalytic activity is attributed to the presence of abundant structural defects and surface active sites on the synthesized Pt-Cu NWs.

scholarly journals Selective Hydrogenation of Naphthalene over γ-Al2O3-Supported NiCu and NiZn Bimetal Catalysts

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1215 ◽  
Author(s):  
Jingqiu Li ◽  
Liu Shi ◽  
Gang Feng ◽  
Zhangping Shi ◽  
Chenglin Sun ◽  
...  
Keyword(s):  
Selective Hydrogenation ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Density Functional ◽  
Surface Engineering ◽  
Rational Surface ◽  
Impregnation Method ◽  
X Ray ◽  
Hydrogenation Activity ◽  
Calculation Results

A series of Cu and Zn modified Ni/Al2O3 catalysts were prepared using an incipient impregnation method for the selective hydrogenation of naphthalene into tetralin. X-ray diffraction (XRD), H2-Temperature programmed reduction (H2-TPR), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were applied to reveal the structure regulation, and density functional theory (DFT) calculations were performed to investigate the electronic effect and reactant adsorptions on the active sites. The results showed that the addition of CuO promoted the hydrogenation of naphthalene with an inhibited tetraline selectivity. However, a simultaneously increasing naphthalene conversion and tetraline selectivity were achieved over the Zn modified Ni/Al2O3 catalysts. The characterization and calculation results revealed that the doping of CuO improved the hydrogenation activity with a low tetralin selectivity due to the H spillover from the Cu. The addition of ZnO decreased the interaction between NiOx and Al2O3 in NiZn/Al2O3 catalysts, which efficiently increased the reduction ability of NiOx species and, thus, improved the naphthalene hydrogenation activity. The electron transfer from ZnO to NiOx weakened the adsorption of tetraline and resulted in increased tetraline selectivity. This work provides insight into developing efficient catalysts for heavy aromatics conversions via rational surface engineering.

scholarly journals Multiplicity of Active-Site in Heterogeneous Ziegler-Natta Catalyst and Its Correlation with Polymer Microstructure

1970 ◽  
Vol 46 (4) ◽  
pp. 487-494
Author(s):  
ATM Kamrul Hasan
Keyword(s):  
Molecular Weight ◽  
Computer Simulation ◽  
Active Site ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Chain Structure ◽  
Surface Complexes ◽  
Polymer Microstructure ◽  
Natta Catalyst ◽  
Ziegler Natta Catalyst

Multiplicity of active-site in heterogeneous Ziegler-Natta catalysts and its correlation with polymer microstructure was studied through the surface structure analysis of catalyst by computer simulation of X-ray Photoelectron Spectroscopy (XPS) data and microstructure investigation of polypropylene chains based on the deconvolution of the molecular weight distribution curves by multiple Flory most probable distributions using Gel Permeation Chromatography (GPC) method. The number and relative intensities of these peaks were found correlated to the distribution of multiple active sites. In this investigation, four individual categories of active sites were identified, each of which yields polypropylene with unique properties of molecular weight and chain structure different from other active sites. The reason of the multiplicity of active sites was determined by the presence of different locations of surface titanium species coordinated with other surface atoms or molecules. These different surface complexes of active species determine the multiple active site nature of catalyst which replicates the microtacticity, molecular weight and chain microstructure distribution of polymer. Keywords: Ziegler-Natta catalyst; Multiple active sites; Flory components; Computer simulation; Deconvolution; MWD. DOI: http://dx.doi.org/10.3329/bjsir.v46i4.9596 BJSIR 2011; 46(4): 487-494

scholarly journals Capping Agent Effect on Pd-Supported Nanoparticles in the Hydrogenation of Furfural

Catalysts ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 11 ◽  
Author(s):  
Shahram Alijani ◽  
Sofia Capelli ◽  
Stefano Cattaneo ◽  
Marco Schiavoni ◽  
Claudio Evangelisti ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Catalytic Performance ◽  
Shielding Effect ◽  
Capping Agents ◽  
X Ray ◽  
Supported Nanoparticles ◽  
Liquid Phase Hydrogenation ◽  
Diallyldimethylammonium Chloride ◽  
Transmission Electron

The catalytic performance of a series of 1 wt % Pd/C catalysts prepared by the sol-immobilization method has been studied in the liquid-phase hydrogenation of furfural. The temperature range studied was 25–75 °C, keeping the H2 pressure constant at 5 bar. The effect of the catalyst preparation using different capping agents containing oxygen or nitrogen groups was assessed. Polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and poly (diallyldimethylammonium chloride) (PDDA) were chosen. The catalysts were characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The characterization data suggest that the different capping agents affected the initial activity of the catalysts by adjusting the available Pd surface sites, without producing a significant change in the Pd particle size. The different activity of the three catalysts followed the trend: PdPVA/C > PdPDDA/C > PdPVP/C. In terms of selectivity to furfuryl alcohol, the opposite trend has been observed: PdPVP/C > PdPDDA/C > PdPVA/C. The different reactivity has been ascribed to the different shielding effect of the three ligands used; they influence the adsorption of the reactant on Pd active sites.

scholarly journals Nitrogen-Doped Sponge Ni Fibers as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Kaili Zhang ◽  
Xinhui Xia ◽  
Shengjue Deng ◽  
Yu Zhong ◽  
Dong Xie ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Photoelectron Spectroscopy ◽  
Oxygen Evolution Reaction ◽  
Active Sites ◽  
High Performance ◽  
Active Phase ◽  
X Ray ◽  
Highly Active ◽  
N Doping ◽  
Energy Conversion Devices

Abstract Controllable synthesis of highly active micro/nanostructured metal electrocatalysts for oxygen evolution reaction (OER) is a particularly significant and challenging target. Herein, we report a 3D porous sponge-like Ni material, prepared by a facile hydrothermal method and consisting of cross-linked micro/nanofibers, as an integrated binder-free OER electrocatalyst. To further enhance the electrocatalytic performance, an N-doping strategy is applied to obtain N-doped sponge Ni (N-SN) for the first time, via NH3 annealing. Due to the combination of the unique conductive sponge structure and N doping, the as-obtained N-SN material shows improved conductivity and a higher number of active sites, resulting in enhanced OER performance and excellent stability. Remarkably, N-SN exhibits a low overpotential of 365 mV at 100 mA cm−2 and an extremely small Tafel slope of 33 mV dec−1, as well as superior long-term stability, outperforming unmodified sponge Ni. Importantly, the combination of X-ray photoelectron spectroscopy and near-edge X-ray adsorption fine structure analyses shows that γ-NiOOH is the surface-active phase for OER. Therefore, the combination of conductive sponge structure and N-doping modification opens a new avenue for fabricating new types of high-performance electrodes with application in electrochemical energy conversion devices.

scholarly journals Supported Gold Nanoparticles as Catalysts in Peroxidative and Aerobic Oxidation of 1-Phenylethanol under Mild Conditions

Nanomaterials ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 151 ◽  
Author(s):  
Ekaterina Pakrieva ◽  
Ana P. C. Ribeiro ◽  
Ekaterina Kolobova ◽  
Luísa M. D. R. S. Martins ◽  
Sónia A. C. Carabineiro ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Density Functional ◽  
Aerobic Oxidation ◽  
Reaction Conditions ◽  
Tert Butyl Hydroperoxide ◽  
Temperature Programmed ◽  
Pretreatment Atmosphere ◽  
Supported Gold Nanoparticles ◽  
Supported Gold

The efficiency of Au/TiO2 based catalysts in 1-phenylethanol oxidation was investigated. The role of support modifiers (La2O3 or CeO2), influence of gold loading (0.5% or 4%) and redox pretreatment atmosphere, catalyst recyclability, effect of oxidant: tert-butyl hydroperoxide (TBHP) or O2, as well as the optimization of experimental parameters of the reaction conditions in the oxidation of this alcohol were studied and compared with previous studies on 1-octanol oxidation. Samples were characterized by temperature-programmed oxygen desorption (O2-TPD) method. X-ray photoelectron spectroscopy (XPS) measurements were carried out for used catalysts to find out the reason for deactivation in 1-phenylethanol oxidation. The best catalytic characteristics were shown by catalysts modified with La2O3, regardless of the alcohol and the type of oxidant. When O2 was used, the catalysts with 0.5% Au, after oxidative pretreatment, showed the highest activity in both reactions. The most active catalysts in 1-phenylethanol oxidation with TBHP were those with 4% Au and the H2 treatment, while under the same reaction conditions, 0.5% Au and O2 treatment were beneficial in 1-octanol oxidation. Despite the different chemical nature of the substrates, it seems likely that Au+(Auδ+) act as the active sites in both oxidative reactions. Density functional theory (DFT) simulations confirmed that the gold cationic sites play an essential role in 1-phenylethanol adsorption.

scholarly journals Synthesis of Phosphorus-Containing Polyanilines by Electrochemical Copolymerization

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1029 ◽  
Author(s):  
Beatriz Martínez-Sánchez ◽  
Andrés Felipe Quintero-Jaime ◽  
Francisco Huerta ◽  
Diego Cazorla-Amorós ◽  
Emilia Morallón
Keyword(s):  
Photoelectron Spectroscopy ◽  
Polymeric Materials ◽  
Electroactive Polymers ◽  
Hydrogen Electrode ◽  
X Ray ◽  
Electrochemical Copolymerization ◽  
Phosphorus Containing ◽  
Redox Transitions ◽  
Acid Stable

In this study, the phosphonation of a polyaniline (PANI) backbone was achieved in an acid medium by electrochemical methods using aminophenylphosphonic (APPA) monomers. This was done through the electrochemical copolymerization of aniline with either 2- or 4-aminophenylphosphonic acid. Stable, electroactive polymers were obtained after the oxidation of the monomers up to 1.35 V (reversible hydrogen electrode, RHE). X-ray photoelectron spectroscopy (XPS) results revealed that the position of the phosphonic group in the aromatic ring of the monomer affected the amount of phosphorus incorporated into the copolymer. In addition, the redox transitions of the copolymers were examined by in situ Fourier-transform infrared (FTIR) spectroscopy, and it was concluded that their electroactive structures were analogous to those of PANI. From the APPA monomers it was possible to synthesize, in a controlled manner, polymeric materials with significant amounts of phosphorus in their structure through copolymerization with PANI.

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