scholarly journals Plasmon-Induced Electrocatalysis with Multi-Component Nanostructures

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 43 ◽  
Author(s):  
Palaniappan Subramanian ◽  
Dalila Meziane ◽  
Robert Wojcieszak ◽  
Franck Dumeignil ◽  
Rabah Boukherroub ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Charge Carriers ◽  
Catalytic Reactions ◽  
Synthetic Methods ◽  
Metal Nanostructures ◽  
Electron Hole ◽  
Catalytic Systems ◽  
Electrochemical Catalysis ◽  
Electrochemically Active ◽  
Shed Light

Noble metal nanostructures are exceptional light absorbing systems, in which electron–hole pairs can be formed and used as “hot” charge carriers for catalytic applications. The main goal of the emerging field of plasmon-induced catalysis is to design a novel way of finely tuning the activity and selectivity of heterogeneous catalysts. The designed strategies for the preparation of plasmonic nanomaterials for catalytic systems are highly crucial to achieve improvement in the performance of targeted catalytic reactions and processes. While there is a growing number of composite materials for photochemical processes-mediated by hot charge carriers, the reports on plasmon-enhanced electrochemical catalysis and their investigated reactions are still scarce. This review provides a brief overview of the current understanding of the charge flow within plasmon-enhanced electrochemically active nanostructures and their synthetic methods. It is intended to shed light on the recent progress achieved in the synthesis of multi-component nanostructures, in particular for the plasmon-mediated electrocatalysis of major fuel-forming and fuel cell reactions.

scholarly journals Selective Styrene Oxidation to Benzaldehyde over Recently Developed Heterogeneous Catalysts

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1680
Author(s):  
Marta A. Andrade ◽  
Luísa M. D. R. S. Martins
Keyword(s):  
Heterogeneous Catalysts ◽  
Carbon Materials ◽  
Oxygen Species ◽  
Styrene Oxidation ◽  
Reaction Conditions ◽  
Reactive Metal ◽  
Catalytic Systems ◽  
Tert Butyl Hydroperoxide ◽  
Metal Organic ◽  
Important Intermediate

The selective oxidation of styrene under heterogeneous catalyzed conditions delivers environmentally friendly paths for the production of benzaldehyde, an important intermediate for the synthesis of several products. The present review explores heterogeneous catalysts for styrene oxidation using a variety of metal catalysts over the last decade. The use of several classes of supports is discussed, including metal–organic frameworks, zeolites, carbon materials and silicas, among others. The studied catalytic systems propose as most used oxidants tert-butyl hydroperoxide, and hydrogen peroxide and mild reaction conditions. The reaction mechanism proceeds through the generation of an intermediate reactive metal–oxygen species by catalyst-oxidant interactions. Overall, most of the studies highlight the synergetic effects among the metal and support for the activity and selectivity enhancement.

scholarly journals Learning from B12 enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

2018 ◽  
Vol 14 ◽  
pp. 2553-2567 ◽  
Author(s):  
Keishiro Tahara ◽  
Ling Pan ◽  
Toshikazu Ono ◽  
Yoshio Hisaeda
Keyword(s):  
Organic Synthesis ◽  
Reaction Mechanisms ◽  
Catalytic Reactions ◽  
Vitamin B ◽  
Catalytic Systems ◽  
New Approach ◽  
Enzyme Functions

Cobalamins (B12) play various important roles in vivo. Most B12-dependent enzymes are divided into three main subfamilies: adenosylcobalamin-dependent isomerases, methylcobalamin-dependent methyltransferases, and dehalogenases. Mimicking these B12 enzyme functions under non-enzymatic conditions offers good understanding of their elaborate reaction mechanisms. Furthermore, bio-inspiration offers a new approach to catalytic design for green and eco-friendly molecular transformations. As part of a study based on vitamin B12 derivatives including heptamethyl cobyrinate perchlorate, we describe biomimetic and bioinspired catalytic reactions with B12 enzyme functions. The reactions are classified according to the corresponding three B12 enzyme subfamilies, with a focus on our recent development on electrochemical and photochemical catalytic systems. Other important reactions are also described, with a focus on radical-involved reactions in terms of organic synthesis.

scholarly journals Nonlinear thermoelectric effects in high-field superconductor-ferromagnet tunnel junctions

2016 ◽  
Vol 7 ◽  
pp. 1579-1585 ◽  
Author(s):  
Stefan Kolenda ◽  
Peter Machon ◽  
Detlef Beckmann ◽  
Wolfgang Belzig
Keyword(s):  
Heat Transport ◽  
Normal Metal ◽  
Hybrid Structures ◽  
Metal Nanostructures ◽  
Thermal Excitation ◽  
Thermoelectric Effects ◽  
Electron Hole ◽  
Metal Structures ◽  
Dc Bias ◽  
Microscopic Origin

Background: Thermoelectric effects result from the coupling of charge and heat transport and can be used for thermometry, cooling and harvesting of thermal energy. The microscopic origin of thermoelectric effects is a broken electron–hole symmetry, which is usually quite small in metal structures. In addition, thermoelectric effects decrease towards low temperatures, which usually makes them vanishingly small in metal nanostructures in the sub-Kelvin regime. Results: We report on a combined experimental and theoretical investigation of thermoelectric effects in superconductor/ferromagnet hybrid structures. We investigate the dependence of thermoelectric currents on the thermal excitation, as well as on the presence of a dc bias voltage across the junction. Conclusion: Large thermoelectric effects are observed in superconductor/ferromagnet and superconductor/normal-metal hybrid structures. The spin-independent signals observed under finite voltage bias are shown to be reciprocal to the physics of superconductor/normal-metal microrefrigerators. The spin-dependent thermoelectric signals in the linear regime are due to the coupling of spin and heat transport, and can be used to design more efficient refrigerators.

scholarly journals Cyclic(Alkyl)(Amino)Carbene Ligands Enable Cu-Catalyzed Markovnikov Protoboration and Protosilylation of Terminal Alkynes: A Versatile Portal to Functionalized Alkenes

2021 ◽  
Author(s):  
Yang Gao ◽  
Sima Yazdani ◽  
Aaron Kendrick ◽  
Glen Junor ◽  
Douglas Grotjahn ◽  
...  
Keyword(s):  
High Selectivity ◽  
Building Blocks ◽  
Terminal Alkynes ◽  
Carbene Ligands ◽  
Catalytic Systems ◽  
General Solutions ◽  
Shed Light ◽  
Limited Scope

Regioselective hydrofunctionalization of alkynes represents a straightforward route to access alkenyl boronate and silane building blocks. In previously reported catalytic systems, high selectivity is achieved with a limited scope of substrates and/or reagents, with general solutions lacking. Herein, we describe a selective copper-catalyzed Markovnikov hydrofunctionalization of terminal alkynes that is facilitated by strongly donating cyclic (alkyl)(amino)carbene (CAAC) ligands. Using this method, both alkyl- and aryl-substituted alkynes are coupled with a variety of boryl and silyl reagents with high α-selectivity. The reaction is scalable, and the products are versatile intermediates that can participate in various downstream transformations. Preliminary mechanistic experiments shed light on the role of CAAC ligands in this process.

scholarly journals Looking for the “Dream Catalyst” for Hydrogen Peroxide Production from Hydrogen and Oxygen

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 251 ◽  
Author(s):  
Federica Menegazzo ◽  
Michela Signoretto ◽  
Elena Ghedini ◽  
Giorgio Strukul
Keyword(s):  
Hydrogen Peroxide ◽  
Heterogeneous Catalysts ◽  
Direct Synthesis ◽  
Particle Morphology ◽  
Synthetic Methods ◽  
Side Reactions ◽  
Catalyst Morphology ◽  
And Performance ◽  
The Ideal

The reaction between hydrogen and oxygen is in principle the simplest method to form hydrogen peroxide, but it is still a “dream process”, thus needing a “dream catalyst”. The aim of this review is to analyze critically the different heterogeneous catalysts used for the direct synthesis of H2O2 trying to determine the features that the ideal or “dream catalyst” should possess. This analysis will refer specifically to the following points: (i) the choice of the metal; (ii) the metal promoters used to improve the activity and/or the selectivity; (iii) the role of different supports and their acidic properties; (iv) the addition of halide promoters to inhibit undesired side reactions; (v) the addition of other promoters; (vi) the effects of particle morphology; and (vii) the effects of different synthetic methods on catalyst morphology and performance.

scholarly journals Photocatalytic water splitting by N-TiO2 on MgO (111) with exceptional quantum efficiencies at elevated temperatures

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Yiyang Li ◽  
Yung-Kang Peng ◽  
Liangsheng Hu ◽  
Jianwei Zheng ◽  
Dharmalingam Prabhakaran ◽  
...  
Keyword(s):  
Water Splitting ◽  
Elevated Temperatures ◽  
Practical Method ◽  
Charge Carriers ◽  
Molar Ratio ◽  
Electron Hole ◽  
Photocatalytic Water Splitting ◽  
The Past ◽  
Electron Hole Pair ◽  
Electric Field Polarization

Abstract Photocatalytic water splitting is attracting enormous interest for the storage of solar energy but no practical method has yet been identified. In the past decades, various systems have been developed but most of them suffer from low activities, a narrow range of absorption and poor quantum efficiencies (Q.E.) due to fast recombination of charge carriers. Here we report a dramatic suppression of electron-hole pair recombination on the surface of N-doped TiO2 based nanocatalysts under enhanced concentrations of H+ and OH−, and local electric field polarization of a MgO (111) support during photolysis of water at elevated temperatures. Thus, a broad optical absorption is seen, producing O2 and H2 in a 1:2 molar ratio with a H2 evolution rate of over 11,000 μmol g−1 h−1 without any sacrificial reagents at 270 °C. An exceptional range of Q.E. from 81.8% at 437 nm to 3.2% at 1000 nm is also reported.

In situ PXRD studies of heterogeneous catalysts and pre-catalysts

2014 ◽  
Vol 70 (a1) ◽  
pp. C1178-C1178
Author(s):  
David Billing
Keyword(s):  
Heterogeneous Catalysts ◽  
Supported Catalysts ◽  
Phase Evolution ◽  
Multiwalled Carbon ◽  
Complex Phase ◽  
Catalytic Systems ◽  
Heterogeneous Processes ◽  
Carbon Nano Tubes ◽  
Diffraction Patterns

During the course of the last couple of years, my collaborators and I have studied a number of catalytic systems using a lab based PXRD facility at our disposal. Of particular interest to us has been the supported catalysts used in Fischer Tropsch catalysis as well as those used in the synthesis of multiwalled carbon nano tubes. These studies have all proven invaluable to the understanding of the often complex phase evolution that is an intricate and inherent part of the heterogeneous processes of interest to us. Selected results will be presented to illustrate the usefulness and value of these studies. For example below is the intensity profile of the diffraction patterns collected during the heat-treatment of the pre-catalyst: A – anatase, R – rutile, S – silicon, H – hematite and P – pseudobrookite

Photocurrent in a hybrid system of 1-thioglycerol and HgTe quantum dots

2003 ◽  
Vol 789 ◽  
Author(s):  
Hyunsuk Kim ◽  
Kyoungah Cho ◽  
Byungdon Min ◽  
Jong Soo Lee ◽  
Man Young Sung ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Hybrid System ◽  
Wavelength Dependence ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
Electron Hole ◽  
Free Carriers ◽  
Transmission Electron ◽  
Colloidal Method ◽  
First Time

ABSTRACTPhotocurrent mechanism in a hybrid system of 1-thioglycerol and HgTe quantum dots(QDs) was studied for the first time in the intra-red (IR) range. 1-thioglycerol-capped HgTe QDs were prepared using colloidal method in aqueous solution; the synthesis and size of the HgTe QDs were examined by x-ray diffraction, Raman scattering, and high-resolution transmission electron microscopy. Absorption and photoluminescence spectra of the capped HgTe QDs revealed the strong excitonic peaks in the range from 900 to 1100nm, because of their widened band gap due to the shrinkage of their sizes to about 3 nm. The wavelength dependence of the photocurrent for the hybred system of the 1-thioglycerol and HgTe QDs was very close to that of the absorption spectrum, indicating that charge carriers photoexcited in the HgTe QDs give direct contribution to the photocurrent in the medium of 1-thioglycerol. In this hybrid system, the photo-excited electrons in the HgTe QDs are strongly confined, but the photo-excited holes act as free carriers. Hence, in the photocurrent mechanism of the this hybrid system, only holes among electron-hole pairs created by incident photons in the HgTe QDs are transferred to 1-thioglycerol surrounding HgTe QDs and contribute photocurrent flowing in the medium of 1-thioglycerol.

scholarly journals Alkaline-Based Catalysts for Glycerol Polymerization Reaction: A Review

2020 ◽  
Author(s):  
Negisa Ebadipour ◽  
Sébastien Paul ◽  
Benjamin Katryniok ◽  
Franck Dumeignil
Keyword(s):  
Heterogeneous Catalysts ◽  
Antimicrobial Agents ◽  
Reaction Medium ◽  
Operating Conditions ◽  
Polymerization Reaction ◽  
High Catalytic Activity ◽  
Catalytic Systems ◽  
Glycerol Conversion ◽  
Advantages And Disadvantages ◽  
Wide Range

Polyglycerols (PGs) are biocompatible and highly functional polyols with a wide range of applications, such as emulsifiers, stabilizers, antimicrobial agents, in many industries including cosmetics, food, plastic and biomedical. The demand increase for biobased PGs encourages researchers to develop new catalytic systems for glycerol polymerization. This review focuses on alkaline homogeneous and heterogeneous catalysts. The performances of the alkaline catalysts are compared in terms of conversion and selectivity, and their respective advantages and disadvantages are commented. While homogeneous catalysts exhibit a high catalytic activity, they cannot be recycled and reused, whereas solid catalysts can be partially recycled. The key issue for heterogenous catalytic systems, which is unsolved so far, is linked to their instability due to partial dissolution in the reaction medium. Further, this paper also reviews the proposed mechanisms of glycerol polymerization over alkaline-based catalysts and discuss the various operating conditions with an impact on the performances. More particularly, temperature and amount of catalyst proved to have a significant influence on glycerol conversion and on its polymerization extent.

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