Advantageous Effects of Phase Transition-Modulated Electric Polarization of Hollow CuSx for Enhanced Electromagnetic Wave Absorption.

Scrutinizing the electromagnetic wave absorption mechanism of sulfides remains a challenge due to the variability of the modulation of the crystal structure of the sulfides. To take advantage of this variability, nanosheet-assembled Cu9S5/CN composites with sulfur vacancies were prepared in this study by self-assembly synthesis and subsequent high-temperature heat treatment. Systematic studies show the phase transition-dependent induced decrease in the conductivity, the defect site-induced difference in the charge density, the weakened vacancy formation of defect polarization loss, and the influence of valence state on electric dipole polarization loss and interfacial polarization loss, making the optimization of the dielectric constant a significant positive effect on the improvement of impedance matching. This work provides a reliable example and theoretical guidance for the crystal structure design for the preparation of a new generation of efficient sulfide-based wave-absorbing materials.

Selenium-induced anion vacancy and active site migration stimulating remarkable sulfide Na-Ion storage.

Heterojunctions and controllable anionic vacancies are perceived to be powerful means of ameliorating the performance of sodium-ion batteries assignable to their unique physical and chemical properties. However, the mechanism by which heterojunction and vacancy structures affect sodium-ion battery storage remains to be systemically explored. In this study, the Se doped CoS2@CoS1.035@Carbon (Se-CoS2@CoS1.035@C) heterostructure with anion vacancy was synthesized by a one-step calcination. These heterostructures with lower metal oxidation states and anionic vacancies exhibit exceptional Na+ storage performance (554.3 mA h g-1 after 1500 cycles at 5.0 A g-1). Both electrochemical tests and theoretical calculations demonstrate excellent pseudocapacitive behavior and enhanced Na+ adsorption during discharge because of anionic vacancies and Se doping. Additionally, introducing weaker Co-Se bonds and extending Co-S and Co-Se bonds reduce binding energies, which effectively accelerates the conversion reaction. Our findings provide a feasible way to rationally design and facilely prepare heterostructured anode materials with rich anionic vacancies for sodium-ion batteries.

Tuning Electromagnetic Parameters Induced by Synergistic Dual-Polarization Enhancement Mechanisms with Amorphous Cobalt Phosphide with Phosphorus Vacancies for Excellent Electromagnetic Wave Dissipation Performance.

The understanding of amorphous and heterojunction materials has been widely used in the field of electromagnetic wave absorption due to their unique physical and chemical properties. However, the effectiveness of individual strategies currently used is still limited. Well-designed compositions and amorphous structures simplify the effect of different polarization mechanisms on the absorption of electromagnetic waves. In this work, through the carbonization and controlled phosphating of one-dimensional Co Metal-Organic Framework (Co-MOF) nanorods, the synthesis of complex components and amorphous CoPx with phosphorus vacancies is successfully accomplished, thus adjusting the optimization of electromagnetic parameters. Phosphorus-vacancy-induced defective polarization loss and enhanced-electronegativity-differences-induced dipole polarization loss synergistically as a dual-polarization strategy significantly improved the electromagnetic parameters and impedance matching. In conclusion, the electromagnetic parameters of the Co@CoPx@C composites are indeed significantly regulated, with reflection losses of -55 dB and a bandwidth of up to 5.5 GHz. These innovative research ideas provide instructive thinking for the development of amorphous absorbers with vacancies.