Fabrication of magnetic Fe 3 O 4 / MnO 2 / TiO 2 /polypyrrole heterostructure for efficient adsorption of Mn 7+ from aqueous solution

Fabrication of the hollow dodecahedral NiCoZn layered double hydroxide for high-performance flexible asymmetric supercapacitor

Layered double hydroxides (LDHs) with unique layered structure have excellent theoretical capacitance. Nevertheless, the constrained availability of electrically active sites and cationic species curtails their feasibility for practical implementation within supercapacitors. Most of the reported materials are bimetallic hydroxides, and fewer studies are on trimetallic hydroxides. In here, the hollow dodecahedron NiCoZn-LDH is synthesized using CoZn metal-organic frameworks (CoZn-MOFs) as template. Its morphology and composition are studied in detail. Concurrently, the effect of the amount of third component on the resulting structure of NiCoZn-LDH is also researched. Benefiting from its favorable structural and compositional attributes to efficient transfer of ions and electrons, NiCoZn-LDH-200 demonstrates outstanding specific capacitance of 1003.3F g-1 at 0.5 A/g. Furthermore, flexible asymmetric supercapacitor utilizing NiCoZn-LDH-200 as the positive electrode and activated carbon (AC) as the negative electrode reveals favorable electrochemical performances, including a notable specific capacitance of 184.7F g-1 at 0.5 A/g, a power density of 368.21 W kg-1 at a high energy density of 65.66 Wh kg-1, an energy density of 31.78 Wh kg-1 at a high power density of 3985.97 W kg-1, a capacitance retention of 92 % after 8000 cycles at 5 A/g, and a good capacitance retention of 90 % after 500 cycles of bending. The template method presented herein can effectively solve the problem of easy accumulation and improve the electrochemical properties of the materials, which exhibits a broad research prospect.

Fabrication of 1D Ni nanochains@Zn2+ doping polypyrrole/reduced graphene oxide composites for high-performance electromagnetic wave absorption

Nowadays, electromagnetic radiation significantly impacts the normal operation of electronic devices and poses risks to human health. To effectively address this problem, the development of composites that exhibit exceptional electrochemical wave absorption through the combination of different components holds great promise. In this study, we have successfully prepared 1D Ni nanochains@Zn2+ doping polypyrrole/reduced graphene oxide (Ni NCs@Z-P/RGO, denoted as R-x) composites using a combination of hydrothermal, solvothermal, in situ polymerization, and physical blending methods. Notably, the R-2 composite demonstrates a remarkable minimum reflection loss (RLmin) of -63.58 dB at 14.3 GHz, with a thickness of 1.61 mm. Furthermore, the R-2 composite exhibits an impressive effective absorption bandwidth (EAB) of 5.08 GHz (11.92 GHz-17 GHz) at a thickness of 1.67 mm. These outstanding performances can be attributed to the synergistic effect of the different components and a well-thought-out structural design. Moreover, to showcase the practical applicability of the material, we have conducted additional investigations on the reduction of the radar cross-sectional area (RCS). The results strongly demonstrate that the prepared composite material, when used as a coating, effectively reduces the RCS value by up to 26.6 dB m2 for R-2 at θ = 0°. The experimental methods and simulations presented in this study hold significant potential for application in wave absorption research and practical implementations. Additionally, the prepared Ni NCs@Z-P/RGO composites demonstrate feasibility as wave-absorbing materials for future utilization.

Fabrication of cobalt-zinc bimetallic oxides@polypyrrole composites for high-performance electromagnetic wave absorption

Composite materials that combine magnetic and dielectric losses offer a potential solution to enhance impedance match and significantly improve microwave absorption. In this study, Co3O4/ZnCo2O4 and ZnCo2O4/ZnO with varying metal oxide compositions are successfully synthesized, which are achieved by modifying the ratios of Co2+ and Zn2+ ions in the CoZn bimetallic metal-organic framework (MOF) precursor, followed by a high-temperature oxidative calcination process. Subsequently, a layer of polypyrrole (PPy) is coated onto the composite surfaces, resulting in the formation of core-shell structures known as Co3O4/ZnCo2O4@PPy (CZCP) and ZnCo2O4/ZnO@PPy (ZCZP) composites. The proposed method allows for rapid adjustments to the metal oxide composition within the inner shell, enabling the creation of composites with varying degrees of magnetic losses. The inclusion of PPy in the outer shell serves to enhance the bonding strength of the entire composite structure while contributing to conductive and dielectric losses. In specific experimental conditions, when the loading is set at 50 wt%, the CZCP composite exhibits an effective absorption bandwidth (EAB) of 5.58 GHz (12.42 GHz-18 GHz) at a thickness of 1.53 mm. Meanwhile, the ZCZP composite demonstrates an impressive minimum reflection loss (RLmin) of -71.2 dB at 13.04 GHz, with a thickness of 1.84 mm. This study offers a synthesis strategy for designing absorbent composites that possess light weight and excellent absorptive properties, thereby contributing to the advancement of electromagnetic wave absorbing materials.

Magnetic Core@Shell Fe3O4@Polypyrrole@Sodium Dodecyl Sulfate Composite for Enhanced Selective Removal of Dyestuffs and Heavy Metal Ions from Complex Wastewater

Adsorption materials have demonstrated huge potential in treating sewage; however, it is a great challenge to fabricate an adsorbent effectively adsorbing multiple dyestuffs and heavy metal ions simultaneously. Here, a magnetic core@shell Fe3O4@polypyrrole@sodium dodecyl sulfate (Fe3O4@PPy@SDS) composite is prepared through the combination of a hydrothermal method, an in situ polymerization method, and modification, exhibiting enhanced selective removal of five dyestuffs (methylene blue (MB), malachite green (MG), rhodamine B (RhB), Congo red (CR), acid red 1 (AR1)), and heavy metal ions (Mn(VII)). The effects of adsorbent type, time, initial concentration of the adsorbate, and temperature on adsorption performances are investigated in detail. Kinetics and isotherm studies indicate that all adsorption processes are more in line with the pseudo-second-order kinetic model and the Langmuir model, the diffusion behavior is controlled by intraparticle diffusion and liquid film diffusion, and research of thermodynamics reveals a spontaneous endothermic behavior. The removal efficiency after five desorption-adsorption cycles can still reach more than 90%. The prepared Fe3O4@PPy@SDS composite is an efficient and promising renewable adsorbent for the treatment of dyestuffs and Mn(VII), exhibiting a wide range of applications in the field of adsorption.