Co@C nanorods as both magnetic stirring nanobars and magnetic recyclable nanocatalysts for microcatalytic reactions

Zhang, Tianyu; Wang, Huijing; Shao, Shiheng; Ding, Lei; Han, Aijuan; Wang, Lianying; Liu, Junfeng

doi:10.1016/j.apcatb.2021.120925

Cited by 15 publications

(5 citation statements)

References 46 publications

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“…As shown in Figure1b, the electrocatalysts, Co, CoO, and Co 3 O 4 , were all successfully prepared. In detail, the 2θ diffraction peaks of the sample after Ar treatment at 44.3, 51.4, and 75.9°matched typical peaks of the (111), (200), and (220) crystal planes of Co,36,37 while the 2θ diffraction peaks of the sample after Ar and air treatment located at 36.6, 42.5, 61.6, and 73.7°were attributed to the (111), (200), (220), and (311) crystal planes of CoO 38. For the sample after calcination in air, the 2θ diffraction peaks at 31.2, 36.7, 44.9, 59.4, and 65.2°were indexed to the (220), (311), (400), (511), and (440) planes of Co 3 O 4 39.…”

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confidence: 83%

Enhanced Alkaline Oxygen Evolution Using Spin Polarization and Magnetic Heating Effects under an AC Magnetic Field

Zheng

Wang

Xie

et al. 2022

ACS Appl. Mater. Interfaces

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Renewable electricity from splitting water to produce hydrogen is a favorable technology to achieve carbon neutrality, but slow anodic oxygen evolution reaction (OER) kinetics limits its large-scale commercialization. Electron spin polarization and increasing the reaction temperature are considered as potential ways to promote alkaline OER. Here, it is reported that in the alkaline OER process under an AC magnetic field, a ferromagnetic ordered electrocatalyst can simultaneously act as a heater and a spin polarizer to achieve significant OER enhancement at a low current density. Moreover, its effect obviously precedes antiferromagnetic, ferrimagnetic, and diamagnetic electrocatalysts. In particular, the noncorrected overpotential of the ferromagnetic electrocatalyst Co at 10 mA cm −2 is reduced by a maximum of 36.6% to 243 mV at 4.320 mT. It is found that the magnetic heating effect is immediate, and more importantly, it is localized and hardly affects the temperature of the entire electrolytic cell. In addition, the spin pinning effect established on the ferromagnetic/paramagnetic interface generated during the reconstruction of the ferromagnetic electrocatalyst expands the ferromagnetic order of the paramagnetic layer. Also, the introduction of an external magnetic field further increases the orderly arrangement of spins, thereby promoting OER. This work provides a reference for the design of high-performance OER electrocatalysts under a magnetic field.

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confidence: 83%

Enhanced Alkaline Oxygen Evolution Using Spin Polarization and Magnetic Heating Effects under an AC Magnetic Field

Zheng

Wang

Xie

et al. 2022

ACS Appl. Mater. Interfaces

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“…Sample homogenization via microfluidic mixing [ 1,2 ] is challenging in systems such as microreactors, [ 3–5 ] confined fluids, [ 6,7 ] and droplets. [ 8–11 ] Owing to the restrictions of microscale devices, most flows in microfluidic channels remain laminar. Thus, molecular diffusion is the primary mixing mechanism in the absence of turbulent chaotic flow.…”

Section: Introductionmentioning

confidence: 99%

“…Sample homogenization via microfluidic mixing [1,2] is challenging in systems such as microreactors, [3][4][5] confined fluids, [6,7] and droplets. [8][9][10][11] Owing to the restrictions of microscale devices, which are based on nonspherical double emulsions afforded by microfluidics, were placed in a microchannel to mix fluids under an external rotating magnetic field. Secondary vortices with cyclical characteristics were generated during agitation of the MNSPs, which helped improve the mixing efficiency and expand the mixing zone at high rotation rates.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Non‐Spherical Particles Inducing Vortices in Microchannel for Effective Mixing

Feng

Pan

et al. 2023

Small

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most flows in microfluidic channels remain laminar. Thus, molecular diffusion is the primary mixing mechanism in the absence of turbulent chaotic flow. [12,13] However, diffusion is slow and inefficient at the typical microfluidic-channel scales of tens to hundreds of micrometers, which necessitates a long distance for sufficient mixing. Various agitation-enhancing strategies-active and passive-have been proposed to address this issue; [3,[14][15][16][17][18][19][20] these refer to mixing that is enhanced by external energy and the construction of channels with specially designed features to induce chaotic advection, respectively.Passive micromixers typically have channels with delicate structures, such as serpentine, [21,22] herringbone, [23,24] and tesla configurations. [25,26] By inducing chaotic advection, these flow topologies produce repetitive stretching, folding, and splitting to increase the interfacial area, thereby effectively enhancing the mixing. [27] Alternatively, rapid mixing can be achieved using active strategies such as magnetism, [28][29][30] ultrasound, [31,32] electrodynamic force, [33,34] and fabrication of flexible walls. [35,36] However, applying these methods to lab-on-chip devices may complicate their design and fabrication. [37] Moreover, these methods are difficult to adapt after the initial fabrication, which hinders their applicability for different systems.Magnetism-based active strategies have attracted considerable attention. Typically, a unique microstructural design is not required to induce a magnetic force. In addition, magnetic force is a noncontact force that is also bio-friendly. [38,39] Typical investigations on the application of magnetism have involved chained magnetic beads, [40][41][42] magnetic artificial cilia, [43] and ferrofluids. [44,45] However, densely concentrated ferrofluids may hinder direct detection and observation. [46] Nanomaterials often require a strong magnetic field and sufficient incubation time for chain formation. [47] Furthermore, precipitation could occur at high nanomaterial concentrations, only stirring at the bottom of drops. [48] Few studies have reported real-time observation and analysis of the flow field during mixing, presumably because of the difficulty in observing and characterizing the micro-scale mixing behavior.In this study, magnetic nonspherical particles (MNSPs) were fabricated to resolve the mixing-related challenges of microchannels and to analyze the mixing mechanism using a micro-particle image velocimetry (µPIV) system. The MNSPs, Mixing in microfluidic channels is dominated by diffusion owing to the absence of chaotic flow. However, high-efficiency microscale mixing over short distances is desired for the development of lab-on-chip systems. Here, enhanced mixing in microchannels achieved using magnetic nonspherical particles (MNSPs), is reported. Benefiting from the nonspherical shape of the MNSPs, secondary vortices exhibiting cyclical characteristics appear in microchannels when the MNSPs rotate under an external magneti...

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“…8 Liu et al reported that a novel nanorod-like Co@CN catalyst with a Co size of 7 nm could be obtained through the pyrolysis of Co(OH)(C 6 H 5 CO 3 )•H 2 O precursor. 9 The Co@CN catalyst shows high stability and can be reused 9 times without obvious loss of activity. However, the catalysts prepared by this method usually exhibit a very wide metal particle size distribution ranging from a few to tens of nanometers.…”

Section: Introductionmentioning

confidence: 99%

“…The obtained NiO x @GCNTs catalyst can maintain its catalytic performance for 165 h for the ethylbenzene dehydrogenation at 550 °C . Liu et al reported that a novel nanorod-like Co@CN catalyst with a Co size of 7 nm could be obtained through the pyrolysis of Co(OH)(C 6 H 5 CO 3 )·H 2 O precursor . The Co@CN catalyst shows high stability and can be reused 9 times without obvious loss of activity.…”

Section: Introductionmentioning

confidence: 99%

Engineering the Structure of ZIF-Derived Hierarchically Porous CoZn Catalysts for Efficient Selective Hydrogenation of Nitroarenes

Cao

Wen

Guan

et al. 2023

Ind. Eng. Chem. Res.

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ZIF-derived metal/carbon materials have received great attention for heterogeneous catalysis because of their versatile tunability; however, most of them are microporousdominated structures, seriously limiting their catalytic performance. Herein, we directly synthesized CoZn@CN catalysts with high specific surface area and pore volume via the facile pyrolysis of CoZn-ZIF/g-C 3 N 4 @PDA composites (g-C 3 N 4 , graphitic carbon nitride; PDA, polydopamine), in which g-C 3 N 4 works as the poreforming agent and template and PDA mainly functions as the carbon source. The optimal catalyst (Co 4 Zn 2 @CN) exhibits superior specific surface area (825.0 m 2 /g) and pore volume (2.4 cm 3 /g), which can remarkably improve the mass transfer efficiency and boost the active site exposure, achieving a TOF of 34.5 h −1 for the selective hydrogenation of 3-nitrostyrene at 80 °C and 1 MPa H 2 . Additionally, the preferential adsorption of the nitro group is confirmed to be the main reason for the general selectivity in the hydrogenation of various functionalized nitroarenes. Finally, the Co 4 Zn 2 @CN catalyst also shows excellent stability and can be reused at least 5 times. We anticipate that such a novel strategy may provide some valuable insights into the synthesis of ZIF-derived catalysts with tunable structures.

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Co@C nanorods as both magnetic stirring nanobars and magnetic recyclable nanocatalysts for microcatalytic reactions

Cited by 15 publications

References 46 publications

Enhanced Alkaline Oxygen Evolution Using Spin Polarization and Magnetic Heating Effects under an AC Magnetic Field

Enhanced Alkaline Oxygen Evolution Using Spin Polarization and Magnetic Heating Effects under an AC Magnetic Field

Magnetic Non‐Spherical Particles Inducing Vortices in Microchannel for Effective Mixing

Engineering the Structure of ZIF-Derived Hierarchically Porous CoZn Catalysts for Efficient Selective Hydrogenation of Nitroarenes

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