scholarly journals Interfacial Electronic Effects in Co@N-Doped Carbon Shells Heterojunction Catalyst for Semi-Hydrogenation of Phenylacetylene

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2776
Author(s):  
Yuan Huang ◽  
Haoting Yan ◽  
Chenyang Zhang ◽  
Yize Wang ◽  
Qinhong Wei ◽  
...  
Keyword(s):  
Schottky Contact ◽  
Supported Catalyst ◽  
Electronic Interaction ◽  
Electronic Effects ◽  
Schottky Effect ◽  
Synthesis Strategy ◽  
Schottky Type ◽  
N Doping ◽  
Shell Forming ◽  
High Work

Metal-supported catalyst with high activity and relatively simple preparation method is given priority to industrial production. In this work, this study reported an easily accessible synthesis strategy to prepare Mott-Schottky-type N-doped carbon encapsulated metallic Co (Co@Np+gC) catalyst by high-temperature pyrolysis method in which carbon nitride (g-C3N4) and dopamine were used as support and nitrogen source. The prepared Co@Np+gC presented a Mott-Schottky effect; that is, a strong electronic interaction of metallic Co and N-doped carbon shell was constructed to lead to the generation of Mott-Schottky contact. The metallic Co, due to high work function as compared to that of N-doped carbon, transferred electrons to the N-doped outer shell, forming a new contact interface. In this interface area, the positive and negative charges were redistributed, and the catalytic hydrogenation mainly occurred in the area of active charges. The Co@Np+gC catalyst showed excellent catalytic activity in the hydrogenation of phenylacetylene to styrene, and the selectivity of styrene reached 82.4%, much higher than those of reference catalysts. The reason for the promoted semi-hydrogenation of phenylacetylene was attributed to the electron transfer of metallic Co, as it was caused by N doping on carbon.

Structure and Bonding in Hexa-tert-butyl-hexa-peri-hexabenzocoronene Sandwich Complexes of Ruthenium

2018 ◽  
Vol 71 (4) ◽  
pp. 222
Author(s):  
Matthias Lein
Keyword(s):  
Electronic Interaction ◽  
Polyaromatic Hydrocarbon ◽  
Electronic Effects ◽  
Aromatic System ◽  
Tert Butyl ◽  
Coordination Sites ◽  
Site Selectivity ◽  
Sterically Demanding ◽  
Close Proximity ◽  
Steric Influence

We evaluate the balance of steric and electronic effects in the site selectivity of the binding of [Rh(Me5Cp)]+ ([RhCp·]+) to the three possible coordination sites of the polyaromatic hydrocarbon (PAH) hexa-tert-butyl-hexa-peri-hexabenzocoronene (HBBC). We find that despite the close proximity of sterically demanding tert-butyl groups to the methyl groups of the Cp* ligand, the extent of steric repulsion is minor compared to electronic interaction from bond formation and that the site selectivity is best explained in terms of the electronics of the (poly) aromatic system. This is in contrast to previous investigations on similar systems with a COD ligand where steric influence has been shown to dominate selectivity.

Transient Photoresponse from Co Schottky Barriers on AlGaN

2000 ◽  
Vol 622 ◽  
Author(s):  
R. Schwarz ◽  
M. Niehus ◽  
L. Melo ◽  
P. Brogueira ◽  
S. Koynov ◽  
...  
Keyword(s):  
Carrier Transport ◽  
Room Temperature ◽  
Laser Excitation ◽  
Short Circuit ◽  
Forward Bias ◽  
Schottky Contact ◽  
Schottky Barriers ◽  
Uv Detector ◽  
Photovoltaic Mode ◽  
High Work

ABSTRACTCo on AlGaN is expected to form a large barrier Schottky contact due to its high work function. We have used this material combination with 18 % of Al in AlxGaN for the study of transient photoresponse in the photovoltaic mode and in secondary photocurrent measurements after pulsed laser excitation. In reverse bias and in short- circuit mode a fast decay with a characteristic time of a few microseconds is dominant at room temperature. This mode is appropriate for UV detector operation. At elevated temperature, a much slower tail extending to several milliseconds is also observed. In forward bias operation the slow tail is dominating at any temperature. We discuss this asymmetry with respect to fast minority carrier collection within the space charge region for primary photocurrents and the slower majority carrier transport in forward bias.

scholarly journals Vertical-Type Ni/GaN UV Photodetectors Fabricated on Free-Standing GaN Substrates

2019 ◽  
Vol 9 (14) ◽  
pp. 2895 ◽  
Author(s):  
Bing Ren ◽  
Meiyong Liao ◽  
Masatomo Sumiya ◽  
Jian Huang ◽  
Linjun Wang ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Schottky Contact ◽  
High Signal ◽  
Threading Dislocation ◽  
High Electron ◽  
Free Standing ◽  
Lower Growth ◽  
Schottky Type ◽  
Lower Growth Rate ◽  
Self Powered

The authors report on a vertical-type visible-blind ultraviolet (UV) Schottky-type photodetector fabricated on a homoepitaxial GaN layer grown on free-standing GaN substrates with a semi-transparent Ni Schottky contact. Owing to the high-quality GaN drift layer with low-density threading dislocation and high electron mobility, the UV photodetector shows a high specific detectivity of more than 1012 Jones and a UV/visible discrimination ratio of ~1530 at −5 V. The photodetector also shows the excellent self-powered photo-response and a high signal-to-noise ratio of more than 104 at zero voltage. It is found that a relatively lower growth rate for the GaN epilayer is preferred to improve the performance of the Schottky-type photodetectors due to the better microstructure and surface properties.

scholarly journals Selective Catalysis for the Reductive Amination of Furfural Towards Furfurylamine by the Graphene-Co-Shelled Cobalt Nanoparticles

2021 ◽  
Author(s):  
Xiuzheng Zhuang ◽  
Jianguo Liu ◽  
Shurong Zhong ◽  
Longlong Ma
Keyword(s):  
Catalytic Activity ◽  
Reductive Amination ◽  
Supported Catalyst ◽  
Cost Effective ◽  
Structural Features ◽  
Carbon Layer ◽  
Electronic Interaction ◽  
Earth Abundant ◽  
Carbon Balances ◽  
Homogenous Catalyst

<p>Amines with functional groups are widely used in the manufacture of pharmaceuticals, agricultural chemicals, polymers, and surfactants; so far, amines are mostly produced via petrochemical routes, which <a></a><a>motivates the sustainable production of amines from renewable resources</a>, such as biomass. Unfortunately, the reductive amination of biomass-derived platforms is now suffering from challenges, e.g. poor <a></a><a>selectivity </a>and carbon balances, because of the restriction of homogenous catalyst. For this reason, we developed an eco-friendly, simplified, and highly effective procedure for the preparation of non-toxic heterogeneous catalyst based on the earth-abundant metals (i.e., cobalt), whose catalytic activity on furfural or other biomass-derived platforms were proved to be broadly available. The corresponding conversion rate and few of side products were also determined so as to optimized the reaction conditions, suggesting that the prepared cobalt-supported catalyst enables easy substitution of –NH<sub>2 </sub>moiety towards functionalized and structurally diverse molecules, even under very mild industrially viable and scalable conditions. More surprisingly, the cobalt-supported catalyst could also be expediently recycled by magnetic bar and still remained the excellent catalytic activity after reusing up to eight times; on another hands, the gram-scale reductive amination catalyzed by the same catalyst exhibited the similar yield of target products in comparison to its smaller scale, which was comparable to the reported heterogeneous noble-based catalysts. And also, results from a series of analytic technologies involving XRD, XPS, TEM/Mapping and <i>in-suit</i> FTIR revealed that the structural features of catalyst are closely in relation to its catalytic mechanisms; in simple terms, <a></a><a>the outer graphitic shell is activated by the electronic interaction between the inner </a><a></a><a>metallic </a>nanoparticles and the carbon layer as well as the induced charge redistribution. In conclusion, this newly developed catalysts enable the synthesis of amines from biomass-derived platforms with satisfied selectivity and carbon balance, providing a cost-effective and sustainable access to the widely application of reductive amination.</p>

scholarly journals Selective Catalysis for the Reductive Amination of Furfural Towards Furfurylamine by the Graphene-Co-Shelled Cobalt Nanoparticles

2021 ◽  
Author(s):  
Xiuzheng Zhuang ◽  
Jianguo Liu ◽  
Shurong Zhong ◽  
Longlong Ma
Keyword(s):  
Catalytic Activity ◽  
Reductive Amination ◽  
Supported Catalyst ◽  
Cost Effective ◽  
Structural Features ◽  
Carbon Layer ◽  
Electronic Interaction ◽  
Earth Abundant ◽  
Carbon Balances ◽  
Homogenous Catalyst

<p>Amines with functional groups are widely used in the manufacture of pharmaceuticals, agricultural chemicals, polymers, and surfactants; so far, amines are mostly produced via petrochemical routes, which <a></a><a>motivates the sustainable production of amines from renewable resources</a>, such as biomass. Unfortunately, the reductive amination of biomass-derived platforms is now suffering from challenges, e.g. poor <a></a><a>selectivity </a>and carbon balances, because of the restriction of homogenous catalyst. For this reason, we developed an eco-friendly, simplified, and highly effective procedure for the preparation of non-toxic heterogeneous catalyst based on the earth-abundant metals (i.e., cobalt), whose catalytic activity on furfural or other biomass-derived platforms were proved to be broadly available. The corresponding conversion rate and few of side products were also determined so as to optimized the reaction conditions, suggesting that the prepared cobalt-supported catalyst enables easy substitution of –NH<sub>2 </sub>moiety towards functionalized and structurally diverse molecules, even under very mild industrially viable and scalable conditions. More surprisingly, the cobalt-supported catalyst could also be expediently recycled by magnetic bar and still remained the excellent catalytic activity after reusing up to eight times; on another hands, the gram-scale reductive amination catalyzed by the same catalyst exhibited the similar yield of target products in comparison to its smaller scale, which was comparable to the reported heterogeneous noble-based catalysts. And also, results from a series of analytic technologies involving XRD, XPS, TEM/Mapping and <i>in-suit</i> FTIR revealed that the structural features of catalyst are closely in relation to its catalytic mechanisms; in simple terms, <a></a><a>the outer graphitic shell is activated by the electronic interaction between the inner </a><a></a><a>metallic </a>nanoparticles and the carbon layer as well as the induced charge redistribution. In conclusion, this newly developed catalysts enable the synthesis of amines from biomass-derived platforms with satisfied selectivity and carbon balance, providing a cost-effective and sustainable access to the widely application of reductive amination.</p>

scholarly journals Green and Scalable Fabrication of Sandwich-like NG/SiOx/NG Homogenous Hybrids for Superior Lithium-Ion Batteries

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2366
Author(s):  
Guilong Liu ◽  
Yilin Wei ◽  
Tiantian Li ◽  
Yingying Gu ◽  
Donglei Guo ◽  
...  
Keyword(s):  
Specific Capacity ◽  
Mechanical Damage ◽  
Lithium Ion ◽  
Electrochemical Kinetics ◽  
Ion Diffusion ◽  
Lithium Storage ◽  
High Specific Capacity ◽  
Synthesis Strategy ◽  
N Doping ◽  
Scalable Synthesis

SiOx is considered as a promising anode for next-generation Li-ions batteries (LIBs) due to its high theoretical capacity; however, mechanical damage originated from volumetric variation during cycles, low intrinsic conductivity, and the complicated or toxic fabrication approaches critically hampered its practical application. Herein, a green, inexpensive, and scalable strategy was employed to fabricate NG/SiOx/NG (N-doped reduced graphene oxide) homogenous hybrids via a freeze-drying combined thermal decomposition method. The stable sandwich structure provided open channels for ion diffusion and relieved the mechanical stress originated from volumetric variation. The homogenous hybrids guaranteed the uniform and agglomeration-free distribution of SiOx into conductive substrate, which efficiently improved the electric conductivity of the electrodes, favoring the fast electrochemical kinetics and further relieving the volumetric variation during lithiation/delithiation. N doping modulated the disproportionation reaction of SiOx into Si and created more defects for ion storage, resulting in a high specific capacity. Deservedly, the prepared electrode exhibited a high specific capacity of 545 mAh g−1 at 2 A g−1, a high areal capacity of 2.06 mAh cm−2 after 450 cycles at 1.5 mA cm−2 in half-cell and tolerable lithium storage performance in full-cell. The green, scalable synthesis strategy and prominent electrochemical performance made the NG/SiOx/NG electrode one of the most promising practicable anodes for LIBs.

Microstructure studies of tungsten silicide schottky contacts on Gaas

1987 ◽  
Vol 45 ◽  
pp. 328-329
Author(s):  
Yih-Cheng Shih ◽  
E. L. Wilkie
Keyword(s):  
Thermal Stability ◽  
Field Effect Transistors ◽  
Schottky Contact ◽  
Schottky Contacts ◽  
Excellent Thermal Stability ◽  
Barrier Heights ◽  
Gaas Substrates ◽  
Film Adhesion ◽  
Threshold Voltages ◽  
Thermal Stability Of

Tungsten silicides (WSix) have been successfully used as the gate materials in self-aligned GaAs metal-semiconductor-field- effect transistors (MESFET). Thermal stability of the WSix/GaAs Schottky contact is of major concern since the n+ implanted source/drain regions must be annealed at high temperatures (∼ 800°C). WSi0.6 was considered the best composition to achieve good device performance due to its low stress and excellent thermal stability of the WSix/GaAs interface. The film adhesion and the uniformity in barrier heights and ideality factors of the WSi0.6 films have been improved by depositing a thin layer of pure W as the first layer on GaAs prior to WSi0.6 deposition. Recently WSi0.1 has been used successfully as the gate material in 1x10 μm GaAs FET's on the GaAs substrates which were sputter-cleaned prior to deposition. These GaAs FET's exhibited uniform threshold voltages across a 51 mm wafer with good film adhesion after annealing at 800°C for 10 min.

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