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Previous studies in the direction of electromagnetic wave absorption (EMW) materials have primarily focused on microstructure design, carbon/magnetic dual-phase structure construction and optimizing impedance matching. Despite previous efforts, there still remains a challenge in the introduction of additional EMW attenuation mechanisms. In this work, we fabricate Fe2O3 nanoneedle arrays grafted onto carbon nanofibers (CNFs) to construct equivalent resistive (R), inductive (L), and capacitive (C) structures, thereby introducing an equivalent RLC circuit loss mechanism. The impact of different quantities of surface resonance units on the EMW absorption capability is investigated by adjusting the electrodeposition time. The results reveal that as the number of resonance units per unit area increases, both the resonance strength and bandwidth are significantly enhanced, which brings about a heightened EMW absorption performance. Fe2O3/CNFs-700 exhibits outstanding EMW absorption performance of −54.5 dB at 1.9 mm and an effective absorption bandwidth of 4.3 GHz. These findings not only contribute to the realm of CNF-based EMW materials but also provide valuable insights for enhancing their performance. [ABSTRACT FROM AUTHOR]

Constructing interfaces in heterostructures is effective for modulating the electronic properties of electrocatalysts. The hollow CoMoO4-Co3O4 heterostructure (HCMCH) was prepared as a bifunctional electrocatalyst for Li-O2 battery. The different components in CoMoO4-Co3O4 heterostructure presented the efficient coupling and enhanced the electrocatalytic activity for aprotic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), in which it improved the obviously reduced overpotential of 300 mV (compared with the pure Ketjen black (KB) electrode), enhanced reversibility of 80% capacity retention after 6 full cycles and the superior cyclability of more than 200 cycles with an optimized strategy. The battery performance of the HCMCH was not only associated with the unique hollow structure and rich active sites but also with coupling interface constructions synergetic effects attaching to the improving conductivity and optimized the discharge conversion. These results suggested that this HCMCH electrocatalyst was a promising candidate for the Li-O2 battery and it gave a novel insight for high performance electrocatalyst designing. [ABSTRACT FROM AUTHOR]

The escalating electromagnetic (EM) pollution issues and the demand to elevate military stealth technology make it imperative to develop cost-effective and high-performance electromagnetic wave (EMW) absorbing materials. In this paper, the flower-like CuS/γ-Fe2O3 van der Waals (vdW) heterostructures have been synthesized via a facile two-step solvothermal approach. The flower-like CuS skeleton increases the attenuation path of EMW while reducing the material density. Different contents of γ-Fe2O3 nanoparticles anchor between the flower-like CuS nanosheets to constitute a heterogeneous structure, which enables dielectric and magnetic loss synergistically to optimize impedance matching and remarkably improve the EMW absorption performance. The minimum reflection loss (RLmin) is −49.36 dB with a thickness of only 1.6 mm and the effective absorption bandwidth (EAB) reaches 4.64 GHz (13.36–18 GHz). By adjusting the thickness of the absorber, the EAB can cover 96% of the GHz band. Notably, the superior absorption of −61.53 dB at middle frequency band can be obtained by adjusting the amount of Fe2O3 addition. In this study, the adjustment of EM parameters and the optimization of impedance matching have been achieved by constructing a novel vdW heterogeneous structure, which provides fresh ideas and references for the design of high-performance EMW absorbing materials. [ABSTRACT FROM AUTHOR]

Co3O4 is considered as one of promising cathode catalysts for lithium oxygen (Li-O2) batteries, which contains both tetrahedral Co2+ sites (Co2+Td) and octahedral Co3+ sites (Co3+Oh). It is important to reveal the effect of optimal geometric configuration and oxidation state of cobalt ion in Co3O4 to improve the performance of Li-O2 batteries. Herein, through regulating the synthesis process, Co2+ and Co3+ sites in Co3O4 were replaced with Zn and Al atoms to form materials with a unique Co site. The Li-O2 batteries based on ZnCo2O4 showed longer cycle life than that of CoAl2O4, suggesting that in Co3O4, the Co3+Oh site is a relatively better geometric configuration than Co2+Td site for Li-O2 batteries. Theoretical calculations revealed that Co3+Oh sites provide higher catalysis activity, regulating the adsorption energy of the intermediate LiO2 and accelerating the kinetics of the reaction in batteries, which further leads to the change of the morphology of the discharge product and ultimately improves the electrochemical performance of the batteries. [ABSTRACT FROM AUTHOR]