Novel Oxidovanadium Complexes with Redox-Active R-Mian and R-Bian Ligands: Synthesis, Structure, Redox and Catalytic Properties

A new monoiminoacenaphthenone 3,5-(CF3)2C6H3-mian (complex 2) was synthesized and further exploited, along with the already known monoiminoacenaphthenone dpp-mian, to obtain oxidovanadium(IV) complexes [VOCl2(dpp-mian)(CH3CN)] (3) and [VOCl(3,5-(CF3)2C6H3-bian)(H2O)][VOCl3(3,5-(CF3)2C6H3-bian)]·2.85DME (4) from [VOCl2(CH3CN)2(H2O)] (1) or [VCl3(THF)3]. The structure of all compounds was determined using X-ray structural analysis. The vanadium atom in these structures has an octahedral coordination environment. Complex 4 has an unexpected structure. Firstly, it contains 3,5-(CF3)2C6H3-bian instead of 3,5-(CF3)2C6H3-mian. Secondly, it has a binuclear structure, in contrast to 3, in which two oxovanadium parts are linked to each other through V=O···V interaction. This interaction is non-covalent in origin, according to DFT calculations. In structures 2 and 3, non-covalent π-π staking interactions between acenaphthene moieties of the neighboring molecules (distances are 3.36–3.40 Å) with an estimated energy of 3 kcal/mol were also found. The redox properties of the obtained compounds were studied using cyclic voltammetry in solution. In all cases, the reduction processes initiated by the redox-active nature of the mian or bian ligand were identified. The paramagnetic nature of complexes 3 and 4 has been proven by EPR spectroscopy. Complexes 3 and 4 exhibited high catalytic activity in the oxidation of alkanes and alcohols with peroxides. The yields of products of cyclohexane oxidation were 43% (complex 3) and 27% (complex 4). Based on the data regarding the study of regio- and bond-selectivity, it was concluded that hydroxyl radicals play the most crucial role in the reaction. The initial products in the reactions with alkanes are alkyl hydroperoxides, which are easily reduced to their corresponding alcohols by the action of triphenylphosphine (PPh3). According to the DFT calculations, the difference in the catalytic activity of 3 and 4 is most likely associated with a different mechanism for the generation of ●OH radicals. For complex 4 with electron-withdrawing CF3 substituents at the diimine ligand, an alternative mechanism, different from Fenton’s and involving a redox-active ligand, is assumed.

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The Relation between Catalytic Activity of CO Oxidation and Support Structure in Oxidation Catalysts using Gold Nanoparticles

MRS Proceedings ◽

10.1557/proc-0900-o03-11 ◽

2005 ◽

Vol 900 ◽

Author(s):

Shiho Nagano ◽

Koji Tajiri ◽

Yutaka Tai

Keyword(s):

Gold Nanoparticles ◽

Catalytic Activity ◽

Co Oxidation ◽

Preparation Method ◽

Surface Condition ◽

Silica Aerogels ◽

High Catalytic Activity ◽

Support Materials ◽

Co Oxidation Reaction ◽

The Difference

ABSTRACTThiol-passivated gold nanoparticles were adsorbed on several kinds of support materials such as titania-coated silica aerogels and xerogels etc., and then the thiol was removed by heat treatment. The catalytic activity of the prepared composites for CO oxidation reaction was measured, and the effects of the support on the catalytic activity were investigated. Density of the supports, namely, whether aerogel supports or xerogel ones, hardly affected the catalytic activity. It was found that the catalysts having high catalytic activity could be obtained by this preparation method, even using the xerogels as the support. Calcination of the supports before adsorption of the gold nanoparticles affected the activity. The difference of the catalytic activity was observed between the composites with same gold nanoparticle size, so it was considered that the surface condition of the support materials affects the state of gold nanoparticles in composite.

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Cu42Ge24Na4—A Giant Trimetallic Sesquioxane Cage: Synthesis, Structure, and Catalytic Activity

Catalysts ◽

10.3390/catal8100484 ◽

2018 ◽

Vol 8 (10) ◽

pp. 484 ◽

Cited By ~ 5

Author(s):

Alena Kulakova ◽

Alexey Bilyachenko ◽

Victor Khrustalev ◽

Yan Zubavichus ◽

Pavel Dorovatovskii ◽

...

Keyword(s):

Catalytic Activity ◽

Nitric Acid ◽

Hydroxyl Radicals ◽

Cost Effective ◽

Catalyst Loading ◽

High Catalytic Activity ◽

Initial Concentration ◽

Alkyl Hydroperoxides ◽

Tert Butyl Hydroperoxide ◽

Oxidative Amidation

Unprecedented germanium-based sesquioxane exhibits an extremely high nuclearity (Cu42Ge24Na4) and unusual encapsulation features. The compound demonstrated a high catalytic activity in the oxidative amidation of alcohols, with cost-effective catalyst loading down to 400 ppm of copper, and in the oxidation of cyclohexane and other alkanes with H2O2 in acetonitrile in the presence of nitric acid. Selectivity parameters and the mode of dependence of initial cyclohexane oxidation rate on initial concentration of the hydrocarbon indicate that the reaction occurs with the participation of hydroxyl radicals and alkyl hydroperoxides are formed as the main primary product. Alcohols have been transformed into the corresponding ketones by the catalytic oxidation with tert-butyl hydroperoxide.

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An Efficient Discovery of Active, Selective and Stable Catalysts for Electrochemical H2O2 Synthesis Through Active Motif Screening

10.26434/chemrxiv.13078913 ◽

2020 ◽

Author(s):

Seoin Back ◽

Jonggeol Na ◽

Zachary Ulissi

Keyword(s):

Catalytic Activity ◽

Dft Calculations ◽

Electrochemical Reduction ◽

High Throughput ◽

High Throughput Screening ◽

Density Functional ◽

H2o2 Production ◽

High Catalytic Activity ◽

Adsorption Sites ◽

O2 Reduction

<div> <div> <div> <p>Electrochemical reduction of O2 provides a clean and decentralized pathway to produce H2O2 compared to the current energy-intensive anthraquinone process. As the electrochemical reduction of O2 proceeds via either two-electron or four-electron path- way, it is thus essential to control the selectivity as well as to maximize the catalytic activity. Siahrostami et al. demonstrated a novel approach to control the reaction pathway by optimizing an adsorption ensemble to tune adsorption sites of reaction intermediates, and identified Pt-Hg catalysts from density functional theory (DFT) calculations and experimentally validated this catalyst (Nat. Mater. 2013, 12, 1137). Inspired by this concept, in this work, we apply a state-of-the-art high-throughput screening to develop O2 reduction catalyst for selective H2O2 production. Starting from Materials Project database, we evaluate activity, selectivity and electrochemical stability. To efficiently perform the screening, we introduce an active motif based approach which pre-screens unpromising materials and only performs DFT calculations for promising materials, which significantly reduce the number of the required calculations. We not only provide a list of promising candidates identified by DFT calculations, but also suggest element species to achieve high catalytic activity or H2O2 selectivity for future experimental attempts. Finally, we discuss a strategy for efficient future high-throughput screening using a machine learning pipeline consisting of a non-linear dimension reduction and a density-based clustering. </p> </div> </div> </div>

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An Efficient Discovery of Active, Selective and Stable Catalysts for Electrochemical H2O2 Synthesis Through Active Motif Screening

10.26434/chemrxiv.13078913.v1 ◽

2020 ◽

Author(s):

Seoin Back ◽

Jonggeol Na ◽

Zachary Ulissi

Keyword(s):

Catalytic Activity ◽

Dft Calculations ◽

Electrochemical Reduction ◽

High Throughput ◽

High Throughput Screening ◽

Density Functional ◽

H2o2 Production ◽

High Catalytic Activity ◽

Adsorption Sites ◽

O2 Reduction

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High Catalytic Activity of Heterometallic (Fe6Na7 and Fe6Na6) Cage Silsesquioxanes in Oxidations with Peroxides

10.20944/preprints201703.0039.v1 ◽

2017 ◽

Author(s):

Alexey I. Yalymov ◽

Alexey N. Bilyachenko ◽

Mikhail M. Levitsky ◽

Alexander A. Korlyukov ◽

Victor N. Khrustalev ◽

...

Keyword(s):

Hydrogen Peroxide ◽

Catalytic Activity ◽

Hydroxyl Radicals ◽

Acetonitrile Solution ◽

High Catalytic Activity ◽

X Ray ◽

Complex Ii ◽

Alkyl Hydroperoxides ◽

Catalytically Active ◽

Very High

Two types of heterometallic (Fe(III),Na) silsesquioxanes [Ph5Si5O10]2[Ph10Si10O21]Fe6(O2‒)2Na7(H3O+)(MeOH)2(MeCN)4.5.1.25(MeCN), I, and [Ph5Si5O10]2[Ph4Si4O8]2Fe6Na6(O2‒)3(MeCN)8.5(H2O)8.44, II, were obtained and characterized. X-Ray studies established distinctive structures of both products, with pair of Fe(III)-O-based triangles surrounded by siloxanolate ligands, giving fascinating cage architectures. Complex II proved to be catalytically active in the formation of amides from alcohols and amines, thus becoming a rare example of metallasilsesquioxanes performing homogeneous catalysis. Benzene, cyclohexane and other alkanes, as well as alcohols, can be oxidized in acetonitrile solution to phenol, the corresponding alkyl hydroperoxides and ketones, respectively, by hydrogen peroxide in air in the presence of catalytic amounts of complex II and trifluoroacetic acid. Thus, the cyclohexane oxidation at 20 °C gave oxygenates in very high for alkanes yield (48% based on alkane). The kinetic behaviour of the system indicates that the mechanism includes the formation of hydroxyl radicals generated from hydrogen peroxide in its interaction with diiron species. The latter are formed via monomerization of starting hexairon complex with further dimerization of the monomers.

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Enhanced catalytic activity of low-Pt content nanocatalysts supported on hollow carbon spheres for the ORR in alkaline media

MRS Advances ◽

10.1557/adv.2020.370 ◽

2020 ◽

Vol 5 (57-58) ◽

pp. 2961-2972

Author(s):

P.C. Meléndez-González ◽

E. Garza-Duran ◽

J.C. Martínez-Loyola ◽

P. Quintana-Owen ◽

I.L. Alonso-Lemus ◽

...

Keyword(s):

Catalytic Activity ◽

Anion Exchange ◽

Average Particle Size ◽

Synthesis Method ◽

Alkaline Media ◽

High Catalytic Activity ◽

Average Particle ◽

Carbon Spheres ◽

Hollow Carbon ◽

Hollow Carbon Spheres

In this work, low-Pt content nanocatalysts (≈ 5 wt. %) supported on Hollow Carbon Spheres (HCS) were synthesized by two routes: i) colloidal conventional polyol, and ii) surfactant-free Bromide Anion Exchange (BAE). The nanocatalysts were labelled as Pt/HCS-P and Pt/HCS-B for polyol and BAE, respectively. The physicochemical characterization of the nanocatalysts showed that by following both methods, a good control of chemical composition was achieved, obtaining in addition well dispersed nanoparticles of less than 3 nm TEM average particle size (d) on the HCS. Pt/HCS-B contained more Pt0 species than Pt/HCS-P, an effect of the synthesis method. In addition, the structure of the HCS remains more ordered after BAE synthesis, compared to polyol. Regarding the catalytic activity for the Oxygen Reduction Reaction (ORR) in 0.5 M KOH, Pt/HCS-P and Pt/HCS-B showed a similar performance in terms of current density (j) at 0.9 V vs. RHE than the benchmark commercial 20 wt. % Pt/C. However, Pt/HCS-P and Pt/HCS-B demonstrated a 6 and 5-fold increase in mass catalytic activity compared to Pt/C, respectively. A positive effect of the high specific surface area of the HCS and its interactions with metal nanoparticles and electrolyte, which promoted the mass transfer, increased the performance of Pt/HCS-P and Pt/HCS-B. The high catalytic activity showed by Pt/HCS-B and Pt/HCS-P for the ORR, even with a low-Pt content, make them promising cathode nanocatalysts for Anion Exchange Membrane Fuel Cells (AEMFC).

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Ordered Intermetallic Nanoparticles with High Catalytic Activity Prepared by an Electrochemically Induced Phase Transformation

10.26434/chemrxiv.8289812 ◽

2019 ◽

Author(s):

Du Sun ◽

yunfei wang ◽

Kenneth Livi ◽

chuhong wang ◽

ruichun luo ◽

...

Keyword(s):

Catalytic Activity ◽

Diffusion Mechanism ◽

Reduction Reaction ◽

Atomic Scale ◽

High Catalytic Activity ◽

Ambient Conditions ◽

Magnetic Devices ◽

Disordered Alloys ◽

Ordered Intermetallic ◽

Intermetallic Nanoparticles

<div> <p>The synthesis of alloys with long range atomic scale ordering (ordered intermetallics) is an emerging field of nanochemistry. Ordered intermetallic nanoparticles are useful for a wide variety of applications such as catalysis, superconductors, and magnetic devices. However, the preparation of nanostructured ordered intermetallics is challenging in comparison to disordered alloys, hindering progress in materials development. We report a process for converting colloidally synthesized ordered intermetallic PdBi<sub>2</sub> to ordered intermetallic Pd<sub>3</sub>Bi nanoparticles under ambient conditions by an electrochemically induced phase transition. The low melting point of PdBi<sub>2</sub> corresponds to low vacancy formation energies which enables the facile removal of the Bi from the surface, while simultaneously enabling interdiffusion of the constituent atoms via a vacancy diffusion mechanism under ambient conditions. The resulting phase-converted ordered intermetallic Pd<sub>3</sub>Bi exhibits 11x and 3.5x higher mass activty and high methanol tolerance for the oxygen reduction reaction compared to Pt/C and Pd/C, respectively,which is the highest reported for a Pd-based catalyst, to the best of our knowledge. These results establish a key development in the synthesis of noble metal rich ordered intermetallic phases with high catalytic activity, and sets forth guidelines for the design of ordered intermetallic compounds under ambient conditions.</p> </div>

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Nickel (II) and oxovanadium (IV) complexes supported on MCM-41 mesoporous and their application in catalytic selective sulfide and thiol oxidation

Combinatorial Chemistry & High Throughput Screening ◽

10.2174/1386207323999201111192649 ◽

2020 ◽

Vol 23 ◽

Author(s):

Mohsen Nikoorazm ◽

Maryam Khanmoradi ◽

Masoumeh Sayadian

Keyword(s):

Catalytic Activity ◽

Room Temperature ◽

Sol Gel ◽

Reaction Times ◽

Significant Loss ◽

Spectral Studies ◽

High Catalytic Activity ◽

Catalytic Systems ◽

Solvent Free Conditions ◽

Mcm 41

Introduction:: MCM-41 was synthesized using the sol-gel method. Then two new transition metal complexes of Nickel (II) and Vanadium (IV), were synthesized by immobilization of adenine (6-aminopurine) into MCM-41 mesoporous. The compounds have been characterized by XRD, TGA, SEM, AAS and FT-IR spectral studies. Using these catalysts provided an efficient and enantioselective procedure for oxidation of sulfides to sulfoxides and oxidative coupling of thiols to their corresponding disulfides using hydrogen peroxide at room temperature. Materials and Methods:: To a solution of sulfide or thiol (1 mmol) and H2O2 (5 mmol), a determined amount of the catalyst was added. The reaction mixture was stirred at room temperature for the specific time under solvent free conditions. The progress of the reaction was monitored by TLC using n-hexane: acetone (8:2). Afterwards, the catalyst was removed from the reaction mixture by centrifugation and, then, washed with dichloromethane in order to give the pure products. Results:: All the products were obtained in excellent yields and short reaction times indicating the high activity of the synthesized catalysts. Besides, the catalysts can be recovered and reused for several runs without significant loss in their catalytic activity. Conclusion:: These catalytic systems furnish the products very quickly with excellent yields and VO-6AP-MCM-41 shows high catalytic activity compared to Ni-6AP-MCM-41.

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Mechanisms of methane decomposition and carbon species oxidation on the Pr0.42Sr0.6Co0.2Fe0.7Nb0.1O3−σ electrode with high catalytic activity

Journal of Materials Chemistry A ◽

10.1039/c5ta07599h ◽

2015 ◽

Vol 3 (45) ◽

pp. 22816-22823 ◽

Cited By ~ 5

Author(s):

Peng Zhang ◽

Guoqing Guan ◽

Deni S. Khaerudini ◽

Xiaogang Hao ◽

Chunfeng Xue ◽

...

Keyword(s):

Catalytic Activity ◽

Carbon Deposition ◽

Methane Decomposition ◽

High Catalytic Activity ◽

Carbon Species

Carbon deposition characteristics on PSCFN and Ni–YSZ due to thermal CH4 decomposition are investigated by using TPR technique.

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Bio-Derived Catalysts: A Current Trend of Catalysts Used in Biodiesel Production

Catalysts ◽

10.3390/catal11070812 ◽

2021 ◽

Vol 11 (7) ◽

pp. 812

Author(s):

Hoang Chinh Nguyen ◽

My-Linh Nguyen ◽

Chia-Hung Su ◽

Hwai Chyuan Ong ◽

Horng-Yi Juan ◽

...

Keyword(s):

Catalytic Activity ◽

Fossil Fuels ◽

Current Trend ◽

Biodiesel Production ◽

High Catalytic Activity ◽

Promising Alternative ◽

Advantages And Disadvantages ◽

Biodiesel Synthesis ◽

Alkali Catalysts ◽

A Current

Biodiesel is a promising alternative to fossil fuels and mainly produced from oils/fat through the (trans)esterification process. To enhance the reaction efficiency and simplify the production process, various catalysts have been introduced for biodiesel synthesis. Recently, the use of bio-derived catalysts has attracted more interest due to their high catalytic activity and ecofriendly properties. These catalysts include alkali catalysts, acid catalysts, and enzymes (biocatalysts), which are (bio)synthesized from various natural sources. This review summarizes the latest findings on these bio-derived catalysts, as well as their source and catalytic activity. The advantages and disadvantages of these catalysts are also discussed. These bio-based catalysts show a promising future and can be further used as a renewable catalyst for sustainable biodiesel production.

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