13 results
Search Results
2. Unprecedented Mo3S4 cluster-catalyzed radical C–C cross-coupling reactions of aryl alkynes and acrylates.
- Author
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Mateu-Campos, Juanjo, Guillamón, Eva, Safont, Vicent S., Junge, Kathrin, Junge, Henrik, Beller, Matthias, and Llusar, Rosa
- Subjects
RADICALS (Chemistry) ,ACRYLATES ,ALKYNES ,CATALYSTS ,CATALYSIS ,HYDROGEN - Abstract
A new method for the generation of benzyl radicals from terminal aromatic alkynes has been developed, which allows the direct cross coupling with acrylate derivatives. Our additive-free protocol employs air-stable diamino Mo
3 S4 cubane-type cluster catalysts in the presence of hydrogen. A sulfur-centered cluster catalysis mechanism for benzyl radical formation is proposed based on catalytic and stoichiometric experiments. The process starts with the cluster hydrogen activation to form a bis(hydrosulfido) [Mo3 (μ3 -S)(μ-S)(μ-SH)2 Cl3 (dmen)3 ]+ intermediate. The reaction of various aromatic terminal alkynes containing different functionalities with a series of acrylates affords the corresponding Giese-type radical addition products. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
3. One-pot three-component synthesis of α-methylated ketones from secondary and primary aryl alcohols.
- Author
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Samser, Shaikh, Biswal, Priyabrata, Mohapatra, Omkar, Pullarat, Sanu Siyad, Meher, Sushanta Kumar, and Venkatasubbaiah, Krishnan
- Subjects
KETONES ,DEUTERIUM ,ALCOHOL ,CATALYSTS ,HYDROGEN - Abstract
One-pot three-component synthesis of α-methylated ketones from secondary and primary alcohols via a triple dehydrogenative method is presented here. This protocol uses a polystyrene-supported catalyst and the catalyst is reused for five runs without any drop in its activity. Detailed mechanistic investigation was carried out with control reactions and deuterium labelling experiments revealed that secondary and primary alcohols act as a hydrogen source in this one-pot synthesis of α-methylated substituted ketones. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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- View/download PDF
4. Recent advances in cobalt-based catalysts for efficient electrochemical hydrogen evolution: a review.
- Author
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Sun, Ran, Huang, Xing, Jiang, Jibo, Xu, Wenxiu, Zhou, Shaobo, Wei, Ying, Li, Mingjing, Chen, Yukai, and Han, Sheng
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HYDROGEN evolution reactions ,COBALT phosphide ,CATALYSTS ,CATALYTIC activity ,DENSITY functional theory ,HYDROGEN ,STRUCTURAL engineers - Abstract
Hydrogen (H
2 ) is a new type of renewable energy that can meet people's growing energy needs and is environmentally friendly. In order to improve the industrial application prospects and electrochemical performance of hydrogen evolution catalysts, extensive research on transition metal materials has been carried out. Among the many catalytic materials, cobalt is an element with potential for the hydrogen evolution reaction (HER) due to its abundant reserves, low cost, and small energy barrier for H adsorption. This review classifies the latest research on cobalt-based catalysts according to the types of compound, including cobalt-based sulfides, phosphides, carbides, borides, oxides, etc., and summarizes the latest research progress of cobalt-based compound catalysts in acidic and alkaline media. Strategies to tune the properties of cobalt-based compound catalysts for high catalytic activity for HER are focused on, including structural engineering, defect engineering, and doping, etc. The advantages and limitations of each modified approach are reviewed. Not only that, but also the catalytic activity and advantages of the catalyst are evaluated by using density functional theory (DFT) calculation-related descriptors, activity evaluation parameters, etc. Finally, limitations and challenges of cobalt-based materials for HER are presented, as well as prospects for future research. This paper aims to understand the chemical and physical factors that affect cobalt-based catalysts, and to find directions for future research on cobalt-based catalysts. [ABSTRACT FROM AUTHOR]- Published
- 2022
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5. Hydrodeoxygenation of guaiacol to phenol using endogenous hydrogen induced by chemo-splitting of water over a versatile nano-porous Ni catalyst.
- Author
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Xiaohong Ren, Zhuohua Sun, Jiqing Lu, Jinling Cheng, Panwang Zhou, Xiaoqiang Yu, Zeming Rong, and Changzhi Li
- Subjects
GUAIACOL ,CATALYSTS ,MONOMERS ,HYDROGEN ,WATER use - Abstract
In this work, an innovative route for upgrading biomass-derived phenolic monomers by "hydrogen-free" hydrodeoxygenation (HDO) was proposed and evaluated. The HDO process was integrated with the activation of water and aqueous phase reforming of in situ generated methanol over a nano-porous Ni catalyst and finally the one-pot approach was established achieving high selectivity of bio-phenol. DFT calculations confirmed the crucial role of the Ni catalyst in the activation of water and the following HDO process. The study of the reaction pathway and the mechanism showed that the initial hydrogen source came from water splitting on the surface of the Ni catalyst, which triggered the fracture of the aromatic ether bond to afford phenol and methanol. The subsequent aqueous phase reforming of methanol generated more hydrogen and further accelerated the HDO process. Under the optimized conditions the conversion of guaiacol reached 41.5% and the selectivity of phenol can be 100% at 160 °C. On further increasing the temperature to 190 °C, a high conversion of 96.3% could be achieved while maintaining the selectivity of phenol to 77.9%. After a smart design of methanol release during the reaction, the conversion and selectivity could be further improved to 90.5% and 90.3%, respectively. Overall, the proposed method demonstrates the feasibility of upgrading oxygen-containing biological compounds in a neat water system integrating chemo-splitting of water with using endogenous hydrogen for self-hydrolysis inhibiting external hydrogen supply. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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6. Hydrogen evolution performance of Co-MOF/H-g-C3N4 composite catalysts with different morphologies under visible light.
- Author
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Liu, Zhenlu, Xu, Jing, Xue, Tong, Liu, Xinyu, Xu, Shengming, and Li, Zezhong
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VISIBLE spectra ,CATALYSTS ,HYDROGEN ,LEAF morphology ,CATALYTIC activity ,COMPOSITE membranes (Chemistry) - Abstract
The importance of photocatalytic hydrogen evolution is increasing in energy research and environmental catalysis. Co-MOF, a metal–organic framework compound with a zeolite topological structure, has the advantage of being a semiconductor in photocatalytic applications. The new composite materials constructed by coupling Co-MOF with traditional semiconductors will significantly stimulate the potential of photocatalysis due to the construction of a heterogeneous interface. We accurately controlled the growth of Co-MOF with different morphologies by adjusting the ratio of raw materials. With the increase of dimethylimidazole, hexagonal prism morphology (Co-MOF-H), leaf morphology (Co-MOF-B), and Daisy morphology (Co-MOF-D) were successively synthesized. The experimental results show that H-g-C
3 N4 has the best catalytic activity when adsorbing hexagonal prism Co-MOF. When the ratio of H-g-C3 N4 reached 125 mg, the optimal hydrogen evolution activity reached 1033 μmol g−1 h−1 . Various characterization methods were used to explain the influence of morphology regulation on the hydrogen evolution ability of Co-MOF and explore the mechanism of hydrogen evolution of Co-MOF/H-g-C3 N4 composite catalysts. [ABSTRACT FROM AUTHOR]- Published
- 2023
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7. Electronic regulation of a core–shell NiSe2 catalyst by Co doping to accelerate hydrogen evolution.
- Author
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Xu, Huakai, Lu, Kebin, Jiang, Chuanhai, Wei, Xiaofei, Wang, Zhifei, Ouyang, Yuguo, and Dai, Fangna
- Subjects
HYDROGEN evolution reactions ,PRECIPITATION (Chemistry) ,CATALYSTS ,ACTIVATION energy ,CHARGE transfer ,HYDROGEN - Abstract
As a narrow bandgap semiconductor, transition metal selenides are promising as excellent electrocatalysts for hydrogen evolution reactions (HERs). Herein, using an ultra-thin MOF as the precursor, a Co-doped core–shell shaped NiSe
2 based catalyst is successfully constructed by a two-step calcination method as an efficient HER catalyst. Experiments and theoretical calculations indicate that the introduction of Co adjusts the electronic structure of Ni and Se, promoting charge transfer and reducing the energy barrier of the rate-limiting step to accelerate the hydrogen precipitation reaction. In addition, the core–shell structure contributes to mass transport, and the outer carbon layer improves the stability of the catalyst. The optimal catalyst (Ni0.75 Co0.25 Se2 @NC) exhibited satisfactory electrocatalytic activity as evidenced by a low overpotential of −143 mV at a current density of −10 mA cm−2 and a small Tafel slope of 37.5 mV dec−1 . This work provides a valuable strategy for fabricating efficient NiSe2 based electrocatalysts for the HER. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
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8. Ni-Directed biphase N-doped Mo2C as an efficient hydrogen evolution catalyst in both acidic and alkaline conditions.
- Author
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Du, Cheng-Feng, Wang, Yaxin, Zhao, Xiangyuan, Wang, Jinjin, Wang, Xiaomei, Wang, Weigang, and Yu, Hong
- Subjects
HYDROGEN evolution reactions ,PHASE transitions ,CATALYSTS ,HYDROGEN - Abstract
The development of efficient and low-cost catalysts is of great significance for the future application of the electrocatalytic hydrogen evolution reaction (HER). Herein, a series of Ni,N co-doped Mo
2 C nanostructures (Nix –Mo2 C/N) with different Ni content levels are fabricated. The phase-directing effect of Ni on Mo2 C/N is observed, which is in charge of the phase transformation of Mo2 C/N from an α- to a β-phase. At the optimized Ni-doping level, biphase Ni15 –Mo2 C/N exhibits outstanding HER activity under both acidic and alkaline conditions. In particular, under alkaline conditions, Ni15 –Mo2 C/N delivers an overpotential of only 105.0 mV, accompanied by a low Tafel slope of 44.96 mV dec−1 . The performance is comparable to commercial 20% Pt/C and higher than most state-of-the-art Mo2 C-based catalysts as well. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
9. NixP and Mn3O4 dual co-catalysts separately deposited on a g-C3N4/red phosphorus hybrid photocatalyst for an efficient hydrogen evolution.
- Author
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Mao, Qinyi, Li, Dandan, and Dong, Yuming
- Subjects
CATALYSTS ,HYDROGEN evolution reactions ,INTERSTITIAL hydrogen generation ,HYDROGEN ,PHOSPHORUS ,CATALYTIC activity ,SURFACE reactions ,OXIDATION-reduction reaction - Abstract
Recently, much attention has been focused on the development of photocatalysts for hydrogen evolution. Up to now, efficient hydrogen generation is still greatly challenging due to the restraints of the surface redox reaction rate, and the introduction of a co-catalyst is one of the keys to this problem. Here, dual non-noble co-catalysts Ni
x P and Mn3 O4 were proposed and prepared on a g-C3 N4 /red phosphorus (CNP) hybrid structure with a high light adsorption capability by a two-step photo-deposition method. The photo-excited charge on the composite catalyst separate and transfer from C3 N4 to red phosphorous due to a type I heterojunction structure. Nix P and Mn3 O4 act as reductive and oxidative co-catalysts, respectively. The hydrogen production rate was 5851.3 μmol g−1 h−1 , 12.4 times that of pure CNP. The consistent catalytic activity in an actual 25 mL flask for hydrogen evolution over eight hours accumulated 245.08 μmol H2 under solar simulated irradiation. This work provides practical reference for the development of a novel inexpensive photocatalyst system. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
10. Heterostructural MoS2/NiS nanoflowers via precise interface modification for enhancing electrocatalytic hydrogen evolution.
- Author
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Zhao, Xiwang, Bao, Jiehua, Zhou, Yuming, Zhang, Yiwei, Sheng, Xiaoli, Wu, Bo, Wang, Yanyun, Zuo, Changjiang, and Bu, Xiaohai
- Subjects
HYDROGEN evolution reactions ,TRANSITION metal chalcogenides ,CATALYSTS ,WATER electrolysis ,HYDROGEN as fuel ,HYDROGEN ,ELECTRIC conductivity - Abstract
Currently, two-dimensional (2D) layered transition metal chalcogenides (TMCs), especially MoS
2 , are attracting widespread attention in the field of water electrolysis. Unfortunately, the catalytic activity of MoS2 is limited to a few edge sites and by its low conductivity. Herein, MoS2 /NiS heterostructures possessing a flower-like morphology were constructed via an accurate thermal treatment process to realize precise interface modification. As expected, through the adjunction of a certain amount of polyvinylpyrrolidone, NiS grew uniformly on the surface of MoS2 nanosheets, thereby forming a large number of visual lattice fringes with a specific interplanar spacing, which promoted a higher electron-transfer efficiency. The better electron-transfer efficiency resulted in a better hydrogen evolution reaction performance, providing an overpotential of 158 mV at 10 mA cm−1 , a Tafel slope of 128.1 mV dec−1 , and significantly long-term durability. Moreover, density functional theory calculation also showed that the precise interface modification of MoS2 /NiS heterostructure exhibited more occupations at the Fermi level, which improved the electrical conductivity. Additionally, the MoS2 /NiS catalysts achieved a moderately lower hydrogen adsorption energy (ΔGH* ), indicating that it had better catalytic hydrogen evolution performance. This work can be extended to design other catalytic materials and for understanding reactions in the fields of energy conversion through theoretical calculations. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
11. Metal-free hydrogen evolution cross-coupling enabled by synergistic photoredox and polarity reversal catalysis.
- Author
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Cao, Jilei, Yang, Xiaona, Ma, Lishuang, Lu, Kanghui, and Zhou, Rong
- Subjects
HYDROGEN evolution reactions ,CATALYSTS ,CATALYSIS ,HYDROGEN ,METALS ,SILANOLS ,FUNCTIONAL groups - Abstract
A synergistic combination of photoredox and polarity reversal catalysis enabled a hydrogen evolution cross-coupling of silanes with H
2 O, alcohols, phenols, and silanols, which afforded the corresponding silanols, monosilyl ethers, and disilyl ethers, respectively, in moderate to excellent yields. The dehydrogenative cross-coupling of Si–H and O–H proceeded smoothly with broad substrate scope and good functional group compatibility in the presence of only an organophotocatalyst 4-CzIPN and a thiol HAT catalyst, without the requirement of any metals, external oxidants and proton reductants, which is distinct from the previously reported photocatalytic hydrogen evolution cross-coupling reactions where a proton reduction cocatalyst such as a cobalt complex is generally required. Mechanistically, a silyl cation intermediate is generated to facilitate the cross-coupling reaction, which therefore represents an unprecedented approach for the generation of silyl cation via visible-light photoredox catalysis. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
12. Synergistic catalytic hydrolysis of ammonia borane to release hydrogen over AgCo@CN.
- Author
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He, Yating, Wu, Jie, Wang, Yi, Long, Yan, and Fan, Guangyin
- Subjects
CATALYTIC hydrolysis ,CATALYSTS ,SODIUM borohydride ,BORANES ,SILVER nanoparticles ,METAL catalysts ,CATALYTIC activity ,HYDROGEN - Abstract
Ag-based materials have features of low-cost and abundance in comparison with Pt-group metals, while their catalytic performance for hydrogen release from ammonia borane (AB) hydrolysis is relatively low. Herein, we report an activity improvement in hydrogen evolution from catalytic AB hydrolysis over a zeolitic imidazolate framework-67-derived Co@CN anchored Ag nanoparticle (NP) catalyst. Attributed to the rich N-dopant and spatial confinement of the Co@CN, small Ag NPs are uniformly distributed on the support (AgCo@CN). The obtained AgCo@CN exhibits excellent catalytic activity with a high turnover frequency of 282.8 min
−1 for AB hydrolysis, outperforming most of the reported Ag-based catalysts and comparable to many Pt-group metal catalysts. The well-distributed Ag NPs with small sizes and the synergistic effect between Ag and Co@CN facilitate the oxidative cleavage of O–H in H2 O molecules and thereby contribute to the boosted catalytic activity of AgCo@CN for AB hydrolysis. This strategy can be extended to synthesize other supported metal NPs with high efficiency for catalytic utilization. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
13. Efficient homogeneous electrocatalytic hydrogen evolution using a Ni-containing polyoxometalate catalyst.
- Author
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Jana, Debu, Kolli, Hema Kumari, Sabnam, Subhashree, and Das, Samar K.
- Subjects
HYDROGEN evolution reactions ,HYDROGEN production ,AQUEOUS solutions ,CATALYSTS ,HYDROGEN ,OVERPOTENTIAL - Abstract
NiCl
2 ·6H2 O ([Ni(H2 O)6 ]2 Cl2 ) per se does not show electrocatalytic hydrogen evolution reaction activity (HER) in an acidic aqueous medium as well as in neutral water. Interestingly, when [Ni(H2 O)6 ]2+ is present in a polyoxovanadate matrix, for example, in the compound K2 [Ni(H2 O)6 ]2 [V10 O28 ]·4H2 O (1), it exhibits homogeneous electrocatalytic HER activity in an acidic aqueous solution with a turn over frequency of 2.1 s−1 and an effective low overpotential of 127 mV at pH 2.3. Compound 1 is the first nickel-containing polyoxometalate catalyst for hydrogen production via homogeneous electrocatalytic proton reduction without its decomposition under electrochemical conditions of HER. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
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