Magnetic vortex core-shell Fe3O4@C nanorings with enhanced microwave absorption performance

Rechargeable Zn-air batteries are under intensive studies because of their high-energy density, low cost, and safety. However, their wide application is prevented by several remaining technical issues, one of which is the lack of suitable bifunctional cathodic catalysts for oxygen reduction reaction (ORR) during discharging and oxygen evolution reaction (OER) during charging. Due to low material cost and wide distribution, carbon-based materials may serve as promising electrocatalysts, while doping heteroatoms such as nitrogen or boron can effectively enhance their catalytic activity. Herein, we pyrolyze a metal-organic framework containing Zn, N, and B as the precursor to synthesize dual-doped and metal-free porous carbon materials as efficient ORR/OER bifunctional electrocatalysts. The surface area of obtained carbon materials can be greatly enhanced by pyrolysis under H 2 -containing atmosphere. In addition, N and B are evenly distributed within the carbon materials due to the crystalline MOF precursor. The resultant carbon materials exhibit high ORR and OER catalytic activities in both half-cell and single-cell battery measurements. Our study has demonstrated for the first time that MOFs can be used as precursors to synthesize metal-free ORR/OER bifunctional cathodic electrocatalysts with great potential in rechargeable Zn-air batteries.

A metal-free ORR/OER bifunctional electrocatalyst derived from metal-organic frameworks for rechargeable Zn-Air batteries

Electromagnetic pollution has been causing a series of problems in people’s life, and electromagnetic absorbers with lightweight and broad absorbing bandwidth properties are widely desired. In this work, novel sandwich-like 2D laminated Fe&TiO2 nanoparticles@C nanocomposites were rationally designed and successfully developed from the MXene–MOFs hybrids. The formation of Fe and rutile-TiO2 nanoparticles sandwiched by the two-dimensional carbon nanosheets provided strong electromagnetic energy attenuation and good impedance matching for electromagnetic wave (EMW) absorption. As expected, the nanocomposites achieved a broad effective absorption bandwidth of 6.5 GHz at a thickness of only 1.6 mm and the minimum reflection loss (RL) value of − 51.8 dB at 6.6 GHz with a thickness of 3 mm. This work not only provides a good design and fabricating concept for the laminated metal and functional nanoparticles@C nanocomposites with good EMW absorption, but also offers an important guideline to fabricate various two-dimensional nanocomposites derived from the MXene precursors.

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Sandwich-Like Fe&TiO 2 @C Nanocomposites Derived from MXene/Fe-MOFs Hybrids for Electromagnetic Absorption

Facile synthesis of nitrogen-doped reduced graphene oxide/nickel-zinc ferrite composites as high-performance microwave absorbers in the X-band

Developing a flexible, lightweight and effective electromagnetic (EM) absorber remains challenging despite being on increasing demand as more wearable devices and portable electronics are commercialized. Herein, we report a flexible and lightweight hybrid paper by a facile vacuum-filtration-induced self-assembly process, in which cotton-derived carbon fibers serve as flexible skeletons, compactly surrounded by other microwave-attenuating components (reduced graphene oxide and Fe3O4@C nanowires). Owing to its unique architecture and synergy of the three components, the as-prepared hybrid paper exhibits flexible and lightweight features as well as superb microwave absorption performance. Maximum absorption intensity with reflection loss as low as − 63 dB can be achieved, and its broadest frequency absorption bandwidth of 5.8 GHz almost covers the entire Ku band. Such a hybrid paper is promising to cope with ever-increasing EM interference. The work also paves the way to develop low-cost and flexible EM wave absorber from biomass through a facile method.

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A Flexible and Lightweight Biomass-Reinforced Microwave Absorber

Enhanced electromagnetic wave absorption of nanoporous Fe3O4 @ carbon composites derived from metal-organic frameworks

Phase engineering reinforced multiple loss network in apple tree-like liquid metal/Ni-Ni3P/N-doped carbon fiber composites for high-performance microwave absorption

The rational construction of microstructure and composition with enhanced Maxwell-Wagner-Sillars effect (MWSE) is still a challenging direction for reinforcing electromagnetic wave (EMW) absorption performance, and the related EMW attenuation mechanism has rarely been elucidated. Herein, MWSE boosted β-chitin/carbon nano-onions/Ni-P composites is prepared according to the heterointerface engineering strategy via facile layer-by-layer electrostatic assembly and electroless plating techniques. The heterogeneous interface is reinforced from the aspect of porous skeleton, nanomaterials and multilayer construction. The composites exhibit competitive EMW response mechanism between the conductive loss and the polarization/magnetic loss, as describing like the story of "The Hare and the Tortoise". As a result, the composites not only achieve a minimum reflection loss (RLmin) of - 50.83 dB and an effective bandwidth of 6.8 GHz, but also present remarkable EMW interference shielding effectiveness of 66.66 dB. In addition, diverse functions such as good thermal insulation, infrared shielding and photothermal performance were also achieved in the hybrid composites as a result of intrinsic morphology and chemicophysics properties. Therefore, we believe that the boosted MWSE open up a novel orientation toward developing multifunctional composites with high-efficient EMW response and thermal management. 

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Heterointerface Engineering of β-Chitin/Carbon Nano-Onions/Ni–P Composites with Boosted Maxwell-Wagner-Sillars Effect for Highly Efficient Electromagnetic Wave Response and Thermal Management

/pdf/heterointerface-engineering-of-b-chitin-carbon-nano-onions-gwiq5eyq.pdf

Xiao Wang

Papers

Enhanced electromagnetic wave absorption of nanoporous Fe3O4 @ carbon composites derived from metal-organic frameworks

Magnetic vortex core-shell Fe3O4@C nanorings with enhanced microwave absorption performance

Phase engineering reinforced multiple loss network in apple tree-like liquid metal/Ni-Ni3P/N-doped carbon fiber composites for high-performance microwave absorption

Heterointerface Engineering of β-Chitin/Carbon Nano-Onions/Ni–P Composites with Boosted Maxwell-Wagner-Sillars Effect for Highly Efficient Electromagnetic Wave Response and Thermal Management

Heterointerface Engineering of β-Chitin/Carbon Nano-Onions/Ni–P Composites with Boosted Maxwell-Wagner-Sillars Effect for Highly Efficient Electromagnetic Wave Response and Thermal Management