Core/shell structured composites of hollow spherical CoFe2O4 and CNTs as absorbing materials

Zhang, Shenli; Qi, Zhengwu; Zhao, Yun; Jiao, Qingze; Ni, Xiang; Wang, Yajiao; Chang, Yu-Jen; Ding, Chenxu

doi:10.1016/j.jallcom.2016.09.324

Cited by 63 publications

(25 citation statements)

References 22 publications

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“…[45] In brief, anhydrous glucose (15 g), Fe(NH 4 ) 2 ·(SO 4 ) 2 ·6H 2 O( 15 mm)a nd CoSO 4 ·7H 2 O( 30 mm)w ere dissolved in deionized water (100 mL). The Co oxides formed on the surfaceo ft he catalysts during OER www.chemsuschem.org were found to be the main active sites, and the inner layer of CoFeP and surface Fe phosphate may also improve the OER capabilities of the catalyst.…”

Section: Discussionmentioning

confidence: 99%

“…Synthesis of yolk-shell-structured Co 0.47 Fe 0.53 Pm icrospheres First, cobalt ferrite microspheres were synthesized according to a previously reported method with some modification. [45] In brief, anhydrous glucose (15 g), Fe(NH 4 ) 2 ·(SO 4 ) 2 ·6H 2 O( 15 mm)a nd CoSO 4 ·7H 2 O( 30 mm)w ere dissolved in deionized water (100 mL). The mixture was stirred for 40 min and then transferred to a Te flon-lined stainless-steel autoclave.…”

Section: Discussionmentioning

confidence: 99%

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Preparation of Yolk–Shell‐Structured Co_xFe_1−xP with Enhanced OER Performance

et al. 2019

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The design and development of low‐cost, highly efficient, and stable electrocatalysts to take the place of noble‐metal catalysts for the oxygen evolution reaction (OER) remain a significant challenge. Herein, the synthesis of yolk–shell‐structured binary transition metal phosphide CoxFe1−xP with different Co/Fe ratios by phosphidation of a cobalt ferrite precursor is reported. The as‐synthesized CoxFe1−xP catalysts were used for the OER. All yolk–shell CoxFe1−xP catalysts with different Co/Fe ratios showed much better performance than the corresponding solid catalyst. The formation of Co oxides on the catalyst surface during OER and the optimal Co/Fe ratio were found to be critical to their activity. Among the as‐prepared CoxFe1−xP catalysts, that with a Co/Fe ratio of 0.47/0.53 (Co0.47Fe0.53P) exhibited the best performance. Co0.47Fe0.53P has an overpotential of 277 mV at a current density of 10 mA cm−2, a Tafel slope of 37 mV dec−1, and superior stability in alkaline medium. The outstanding performance is partly ascribed to the transfer of valence electrons from Co to P and Fe. The Co0.47Fe0.53P matrix with excellent conductivity and Fe phosphate that is stable on the surface of the catalyst are also helpful for the OER performance. In addition, the yolk–shell structure of Co0.47Fe0.53P increases the contact area between electrolyte and catalyst. These characteristics of Co0.47Fe0.53P greatly improve its OER performance. This optimized binary transition metal phosphide provides a new approach for the design of nonprecious‐metal electrocatalysts.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Preparation of Yolk–Shell‐Structured Co_xFe_1−xP with Enhanced OER Performance

et al. 2019

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“…According to the microwave absorption mechanism, when absorbers have magnetic loss, dielectric loss, and impedance match, more microwaves can enter the interior of the materials and be converted into other forms of energy and dissipated [8,9]. In past decades, many efforts were devoted to researching composites for enhancing microwave absorption, such as (Fe, Ni, Co)/C [10][11][12], (Fe, Ni, Co)/rGO [13][14][15], MFe 2 O 4 /rGO (M = Fe, Ni, Co) [16][17][18][19], MFe 2 O 4 / CNTs [20][21][22], and NiO/SiO 2 /Fe 3 O 4 /rGO [23,24]. However, these materials have the shortcoming of narrow absorption bands, which seriously hinders their practical applications.…”

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Rational Construction of Hierarchically Porous Fe–Co/N-Doped Carbon/rGO Composites for Broadband Microwave Absorption

Wang

et al. 2019

Nano-Micro Lett.

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HIGHLIGHTS• Hierarchically porous Fe-Co/N-doped carbon/rGO (Fe-Co/NC/rGO) composites were successfully prepared. Macropores, mesopores, and micropores coexisted in the composites.• Hierarchically porous Fe-Co/NC/rGO showed effective bandwidth of 9.29 GHz.ABSTRACT Developing lightweight and broadband microwave absorbers for dealing with serious electromagnetic radiation pollution is a great challenge. Here, a novel Fe-Co/N-doped carbon/reduced graphene oxide (Fe-Co/NC/rGO) composite with hierarchically porous structure was designed and synthetized by in situ growth of Fe-doped Cobased metal organic frameworks (Co-MOF) on the sheets of porous cocoon-like rGO followed by calcination. The Fe-Co/NC composites are homogeneously distributed on the sheets of porous rGO. The Fe-Co/NC/rGO composite with multiple components (Fe/Co/NC/rGO) causes magnetic loss, dielectric loss, resistance loss, interfacial polarization, and good impedance matching. The hierarchically porous structure of the Fe-Co/NC/rGO enhances the multiple reflections and scattering of microwaves. Compared with the Co/NC and Fe-Co/NC, the hierarchically porous Fe-Co/NC/rGO composite exhibits much better microwave absorption performances due to the rational composition and porous structural design. Its minimum reflection loss (RL min ) reaches − 43.26 dB at 11.28 GHz with a thickness of 2.5 mm, and the effective absorption frequency (RL ≤ − 10 dB) is up to 9.12 with the same thickness of 2.5 mm. Moreover, the widest effective bandwidth of 9.29 GHz occurs at a thickness of 2.63 mm. This work provides a lightweight and broadband microwave absorbing material while offering a new idea to design excellent microwave absorbers with multicomponent and hierarchically porous structures.

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“…Due to the high proportion of atoms on the surface of the particles, nanomaterials are prone to interface polarization, which can cause multiple scattering. Moreover, nanomaterials show quantum size effects, which split the electron energy levels of particles, and the splitting interval corresponds to the energy range of electromagnetic waves, which opens a new absorption channel [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Effect of Ball Milling on the Absorption Properties of Fe3O4

Liang¹,

Yuan²,

Huang³

et al. 2020

Materials

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FeCl3∙6H2O was used as raw material to produce Fe3O4, using the solvothermal method with ethylene glycol as the solvent. Fe3O4, with different particle sizes, was obtained via mechanical ball-milling by controlling the milling time. Effect of the milling time on the structure, morphology, and electromagnetic parameters of Fe3O4 were studied, and the absorption properties and mechanism of Fe3O4, for different milling times were analyzed. The results showed that the integrity of the original small spherical structure decreased as the ball milling time increased. Fe3O4 showed excellent microwave absorptions as the milling time reached 2 h, the reflection loss reached the maximum of −21.19 dB at 4.64 GHz as the thickness was 6.55 mm.

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Core/shell structured composites of hollow spherical CoFe2O4 and CNTs as absorbing materials

Cited by 63 publications

References 22 publications

Preparation of Yolk–Shell‐Structured Co_xFe_1−xP with Enhanced OER Performance

Preparation of Yolk–Shell‐Structured Co_xFe_1−xP with Enhanced OER Performance

Rational Construction of Hierarchically Porous Fe–Co/N-Doped Carbon/rGO Composites for Broadband Microwave Absorption

Effect of Ball Milling on the Absorption Properties of Fe3O4

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Core/shell structured composites of hollow spherical CoFe2O4 and CNTs as absorbing materials

Cited by 63 publications

References 22 publications

Preparation of Yolk–Shell‐Structured CoxFe1−xP with Enhanced OER Performance

Preparation of Yolk–Shell‐Structured CoxFe1−xP with Enhanced OER Performance

Rational Construction of Hierarchically Porous Fe–Co/N-Doped Carbon/rGO Composites for Broadband Microwave Absorption

Effect of Ball Milling on the Absorption Properties of Fe3O4

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Preparation of Yolk–Shell‐Structured Co_xFe_1−xP with Enhanced OER Performance

Preparation of Yolk–Shell‐Structured Co_xFe_1−xP with Enhanced OER Performance