scholarly journals Unexpected High Selectivity for Acetate Formation from CO2 Reduction with Copper Based 2D Hybrid Catalysts at Ultralow Potentials

2021 ◽  
Author(s):  
Rongming Cai ◽  
Mingzi Sun ◽  
Jiazheng Ren ◽  
Min Ju ◽  
Xia Long ◽  
...  
Keyword(s):  
High Selectivity ◽  
Co2 Reduction ◽  
Catalytic Performance ◽  
Active Species ◽  
Rapid Decay ◽  
Hybrid Catalysts ◽  
Commodity Chemicals ◽  
Acetate Formation

Copper-based catalysts are efficient for CO2 reduction affording commodity chemicals. However, the Cu(I) active species are easily reduced to Cu(0) during CO2RR, leading to rapid decay of catalytic performance. Herein,...

The Effects of Preparation Methods on Iron Structures of Iron-Supported HZSM-5 and their Catalytic Performance for Methanol Dehydration

2016 ◽  
Vol 723 ◽  
pp. 633-639
Author(s):  
Waenkaew Pantupho ◽  
Arthit Neramittagapong ◽  
Nuttawut Osakoo ◽  
Jatuporn Wittayakun ◽  
Sirinuch Loiha
Keyword(s):  
Flow Reactor ◽  
Fixed Bed ◽  
Catalytic Performance ◽  
Active Species ◽  
Iron Complex ◽  
Methanol Dehydration ◽  
Low Carbon ◽  
Zeolite Framework ◽  
Preparation Methods ◽  
Binuclear Iron

Iron-supported HZSM-5 catalysts were prepared by hydrothermal (Fe-HZSM-5_HYD) and impregnation methods (Fe/HZSM-5_IMP). The active species of binuclear-iron complex and iron-substituted zeolite framework, confirmed by EXAFS analysis, were observed on Fe/HZSM-5_IMP and Fe-HZSM-5_HYD, respectively. The catalysts were used for production of dimethyl ether (DME) by methanol dehydration at 200-350 °C using fixed bed flow reactor. Fe/HZSM-5_IMP showed higher catalytic conversion than Fe-HZSM-5_HYD. However, the Fe/HZSM-5_IMP catalyst was less selective to DME product and strongly deactivated for 24h. The deactivation might due to transformation of binuclear-iron to the a-iron site which was strong acidic strengh. The iron-substituted zeolite framework of Fe-HZSM-5_HYD showed high stability toward methanol dehydration. Moreover, the catalyst showed advantages of good selective to DME and low carbon deposition on surface. These results suggested that the iron-substituted zeolite framework structure could improve catalytic performance for mrthanol dehydration.

scholarly journals CuZnAl-Oxide Nanopyramidal Mesoporous Materials for the Electrocatalytic CO2 Reduction to Syngas: Tuning of H2/CO Ratio

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3052
Author(s):  
Hilmar Guzmán ◽  
Daniela Roldán ◽  
Adriano Sacco ◽  
Micaela Castellino ◽  
Marco Fontana ◽  
...  
Keyword(s):  
Noble Metals ◽  
Co2 Reduction ◽  
Reduction Process ◽  
Mesoporous Structure ◽  
Catalytic Performance ◽  
H2 Production ◽  
Ambient Conditions ◽  
Transfer Resistance ◽  
Faradaic Efficiency ◽  
Co2 Electroreduction

Inspired by the knowledge of the thermocatalytic CO2 reduction process, novel nanocrystalline CuZnAl-oxide based catalysts with pyramidal mesoporous structures are here proposed for the CO2 electrochemical reduction under ambient conditions. The XPS analyses revealed that the co-presence of ZnO and Al2O3 into the Cu-based catalyst stabilize the CuO crystalline structure and introduce basic sites on the ternary as-synthesized catalyst. In contrast, the as-prepared CuZn- and Cu-based materials contain a higher amount of superficial Cu0 and Cu1+ species. The CuZnAl-catalyst exhibited enhanced catalytic performance for the CO and H2 production, reaching a Faradaic efficiency (FE) towards syngas of almost 95% at −0.89 V vs. RHE and a remarkable current density of up to 90 mA cm−2 for the CO2 reduction at −2.4 V vs. RHE. The physico-chemical characterizations confirmed that the pyramidal mesoporous structure of this material, which is constituted by a high pore volume and small CuO crystals, plays a fundamental role in its low diffusional mass-transfer resistance. The CO-productivity on the CuZnAl-catalyst increased at more negative applied potentials, leading to the production of syngas with a tunable H2/CO ratio (from 2 to 7), depending on the applied potential. These results pave the way to substitute state-of-the-art noble metals (e.g., Ag, Au) with this abundant and cost-effective catalyst to produce syngas. Moreover, the post-reaction analyses demonstrated the stabilization of Cu2O species, avoiding its complete reduction to Cu0 under the CO2 electroreduction conditions.

scholarly journals Preparation and Photocatalytic Performances of WO3/TiO2 Composite Nanofibers

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xiuping Han ◽  
Binghua Yao ◽  
Keying Li ◽  
Wenjing Zhu ◽  
Xuyuan Zhang
Keyword(s):  
Photoelectron Spectroscopy ◽  
Photocatalytic Oxidation ◽  
Composite Nanofibers ◽  
Photogenerated Electron ◽  
Xrd Analysis ◽  
Catalytic Performance ◽  
Active Species ◽  
X Ray ◽  
Bet Analysis ◽  
Electron Holes

The use of sunlight for photocatalytic oxidation is an ideal strategy, but it is limited by factors such as insufficient light absorption intensity of the photocatalyst and easy recombination of photogenerated electron holes. TiO2 is favored by researchers as an environment-friendly catalyst. In this paper, TiO2 is combined with WO3 to obtain a nanofiber with excellent catalytic performance under sunlight. The WO3/TiO2 composite nanofibers were synthesized by using the electrospinning method. The X-ray diffraction (XRD) analysis indicated that WO3 was successfully integrated onto the surface of TiO2. The photodegradation performance and photocurrent analysis of the prepared nanofibers showed that the addition of WO3 really improved the photocatalytic performance of TiO2 nanofibers, methylene blue (MB) degradation rate increased from 72% to 96%, and 5% was the optimal composite mole percentage of W to Ti. The scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectra (UV-Vis DRS), and Brunauer-Emmett-Teller (BET) analysis further characterized the properties of 5% WO3/TiO2 nanofibers. The H2 generation rate of 5% WO3/TiO2 nanofibers was 107.15 μmol·g−1·h−1, in comparison with that of TiO2 nanofibers (73.21 μmol·g−1·h−1) under the same condition. The 5% WO3/TiO2 produced ·OH under illumination, which played an important role in the MB degradation. Also, the enhanced photocatalytic mechanism was also proposed based on the detailed analysis of the band gap and the active species trapping experiment. The results indicated that the effective separation of Z-scheme photogenerated electron-hole pairs and transfer system constructed between TiO2 and WO3 endowed the excellent photocatalytic activity of 5% WO3/TiO2 nanofibers.

Catalytic Performance of Copper-Substituted Polyoxotungstate Materials and X-Ray Structure of a New Sandwich-Type Compound

2008 ◽  
Vol 587-588 ◽  
pp. 538-542 ◽  
Author(s):  
Salete S. Balula ◽  
Luís Cunha-Silva ◽  
Isabel C.M.S. Santos ◽  
Filipe A. Almeida Paz ◽  
João Rocha ◽  
...  
Keyword(s):  
Potassium Salt ◽  
Room Temperature ◽  
High Selectivity ◽  
Catalytic Performance ◽  
New Materials ◽  
X Ray Diffraction ◽  
Good Efficiency ◽  
X Ray ◽  
Sandwich Type ◽  
Copper Centre

Mono-substituted and sandwich-type copper substituted polyoxoanions ([PW11CuO39]5− and [Cu4(H2O)2(PW9O34)2]10−) were studied as catalysts for the epoxidation of cyclooctene and geraniol, using the green oxidant H2O2, with the results suggesting good efficiency at room temperature. High selectivity and reasonable conversion data were found after the first minutes of reaction. The copper centre may be responsible for this performance and our on-going research focuses in the preparation of new materials incorporating copper into polyoxometalates (POMs). In this context, we have also isolated a new crystalline dimeric sandwich-type polyoxocoppertungstate {H7.05[Cu3WO(H2O)(CuW9O34)(Cu0.6W9O34)]}7.75−. This compound was isolated as potassium salt and structurally characterized by FTIR and single-crystal X-ray diffraction (XRD). The polyoxoanion is composed by the [CuW9O34]12− and [Cu0.6W9O34]12.8− anionic fragments, joined together by a rhomb-like arrangement of three Cu2+ and one W6+ metallic centres, all exhibiting octahedral coordination geometries.

scholarly journals Highly Active Trifloaluminate Ionic Liquids as Recyclable Catalysts for Green Oxidation of 2,3,6-Trimethylphenol to Trimethyl-1,4-Benzoquinone

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1469
Author(s):  
Piotr Latos ◽  
Agnieszka Siewniak ◽  
Natalia Barteczko ◽  
Sebastian Jurczyk ◽  
Sławomir Boncel ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Ionic Liquids ◽  
High Selectivity ◽  
Active Phase ◽  
Catalytic Performance ◽  
Reaction Parameters ◽  
Multiwalled Carbon ◽  
Highly Active ◽  
Recyclable Catalysts ◽  
Fold Excess

An effective method for the synthesis of 2,3,6-trimethyl-1,4-benzoquinone via the oxidation of 2,3,6-trimethylphenol as the key step in the in the preparation of vitamin E was presented. An aqueous solution of H2O2 was used as the oxidant and Lewis acidic trifloaluminate ionic liquids [emim][OTf]-Al(OTf)3, χAl(OTf)3 = 0.25 or 0.15 as catalysts. Trifloaluminate ionic liquids were synthesised by the simple reaction between 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (triflate) [emim][OTf] and aluminium triflate used in sub-stoichiometric quantities. The influence of the reaction parameters on the reaction course, such as the amount and concentration of the oxidant, the amount of catalyst, the amount and the type of organic solvent, temperature, and the reaction time was investigated. Finally, 2,3,6-trimethyl-1,4-benzoquinone was obtained in high selectivity (99%) and high 2,3,6-trimethylphenol conversion (84%) at 70 °C after 2 h of oxidation using a 4-fold excess of 60% aqueous H2O2 and acetic acid as the solvent. The catalytic performance of trifloaluminate ionic liquids supported on multiwalled carbon nanotubes (loading of active phase: 9.1 wt.%) was also demonstrated. The heterogeneous ionic liquids not only retained their activity compared to the homogenous counterparts, but also proved to be a highly recyclable catalysts.

Plasma-induced oxygen vacancies in amorphous MnOx boost catalytic performance for electrochemical CO2 reduction

Nano Energy ◽  
2021 ◽  
Vol 79 ◽  
pp. 105492
Author(s):  
Hyunsu Han ◽  
Song Jin ◽  
Seongmin Park ◽  
Yoongon Kim ◽  
Daehee Jang ◽  
...  
Keyword(s):  
Oxygen Vacancies ◽  
Co2 Reduction ◽  
Catalytic Performance ◽  
Electrochemical Co2 Reduction

scholarly journals Multielectron transportation of polyoxometalate-grafted metalloporphyrin coordination frameworks for selective CO2-to-CH4 photoconversion

2019 ◽  
Author(s):  
Qing Huang ◽  
Jiang Liu ◽  
Liang Feng ◽  
Qi Wang ◽  
Wei Guan ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
High Selectivity ◽  
Energy Resource ◽  
Co2 Reduction ◽  
Reduction Process ◽  
Hydrocarbon Fuel ◽  
Energy Carriers ◽  
Reducing Ability ◽  
Selective Generation ◽  
Coordination Frameworks

Abstract Photocatalytic CO2 reduction into energy carriers is of utmost importance due to the rising concentrations of carbon dioxide and the depleting energy resource. However, the highly selective generation of desirable hydrocarbon fuel, such as methane (CH4), from CO2 remains extremely challenging. Herein, we present two stable polyoxometalate-grafted metalloporphyrin coordination frameworks (POMCFs), which are constructed with reductive Zn-ε-Keggin clusters and photosensitive TCPP linkers, exhibiting high selectivity (> 96%) for CH4 formation in photocatalytic CO2 reduction system. To our knowledge, the high CH4 selectivity of POMCFs has surpassed all of the reported coordiantion framework-based heterogeneous photocatalysts for CO2-to-CH4 conversion. Significantly, the introduction of Zn-ε-keggin cluster with strong reducing ability is the important origin for POMCFs to obtain high photocatalytic selectivity for CH4 formation, considering that eight MoV atoms can theoretically donate eight electrons to fulfill the multi-electrons reduction process of CO2 to CH4 transformation.

scholarly journals A Z-scheme photocatalyst constructed with an yttrium–tantalum oxynitride and a binuclear Ru(ii) complex for visible-light CO2 reduction

2016 ◽  
Vol 52 (50) ◽  
pp. 7886-7889 ◽  
Author(s):  
Kanemichi Muraoka ◽  
Hiromu Kumagai ◽  
Miharu Eguchi ◽  
Osamu Ishitani ◽  
Kazuhiko Maeda
Keyword(s):  
Visible Light ◽  
Band Gap ◽  
High Selectivity ◽  
Co2 Reduction ◽  
Very High ◽  
Hybrid Photocatalyst

A hybrid photocatalyst composed of an yttrium–tantalum oxynitride (with a 2.1 eV band gap) and a binuclear Ru(ii) complex containing both photosensitizing and catalytic units was capable of reducing CO2 to HCOOH with very high selectivity (>99%) under visible light (>400 nm) irradiation.

Fructose conversion in the presence of Sn(iv) catalysts exhibiting high selectivity to lactic acid

RSC Advances ◽  
2015 ◽  
Vol 5 (110) ◽  
pp. 90952-90959 ◽  
Author(s):  
Jailma Barros dos Santos ◽  
Nilson José Araújo de Albuquerque ◽  
Carmen Lúcia de Paiva e Silva Zanta ◽  
Mario Roberto Meneghetti ◽  
Simoni Margareti Plentz Meneghetti
Keyword(s):  
Lactic Acid ◽  
High Selectivity ◽  
Catalytic Performance ◽  
Organometallic Complexes ◽  
Reaction Conditions

The catalytic performance of a series of Sn(iv)-based organometallic complexes in fructose conversion was studied under several reaction conditions, and the conversion, yields, and selectivity measurements of this transformation have been evaluated.

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