Synthesis of a one-dimensional carbon nanotube-decorated three-dimensional crucifix carbon architecture embedded with Co7Fe3/Co5.47N nanoparticles for high-performance microwave absorption

Electro-activated peroxymonosulfate based on hollow cubic skeleton nanoflower cathode catalyst MoSe2/cubic nanocage (CNC) for enhanced degradation of norfloxacin: Performance, mechanism, degradation pathways and toxicity

Recently, antibiotic wastewater pollution has become increasingly serious. In this study, a novel hollow cubic framework self-supported nanoflower-like cathode catalyst (MoSe2/CNC) based on Co Fe prussian blue analogues (CoFePBA)-derived cubic nanocage (CNC) loaded with MoSe2 was successfully prepared and utilized in an electro-activated peroxymonosulfate (PMS) system for norfloxacin (NOR) degradation. Benefit from the combined structures of MoSe2, MoC, and Co/FeNC, the electrocatalytic activity and specific surface area were greatly improved. The effects of catalyst dosage and ratio, current, PMS concentration, electrolyte type, pH, as well as initial concentration were comprehensively investigated. Under the optimal conditions, NOR and TOC removal reached 92.70% and 82.17%, respectively, which was superior to the previous studies. Additionally, ·O2- was proved to be the primary reactive species for NOR degradation.·Based on density functional theory (DFT) and intermediates analysis, NOR underwent substitution and ring-opening reactions in the piperazine ring, substitution of fluoride ions, and cleavage of the carboxyl group and tetrahydropyridine ring, ultimately converting into water, carbon dioxide, and inorganic ions. Moreover, toxicity assessment and seed germination experiments demonstrated that the toxicity of NOR and intermediates were strongly decreased by electro-activated PMS system based on MoSe2/CNC cathode. Overall, this study not only contributes to the evolution of efficient and sustainable wastewater purification technology, but also provides valuable insights into the degradation of antibiotic wastewater.

Preparation of an Fe3O4 Nanoparticle/Carbonized Hemp Fiber Composite with Superior Microwave Absorption Performance

The increasing concern over the negative impact of electromagnetic radiation and interference on humans has led to a growing interest in microwave-absorbing materials that are cost-effective, have a wide frequency range, and have high efficiency. In this paper, an Fe3O4 nanoparticle/carbonized hemp fiber composite was successfully prepared using hemp fibers as the primary material and template. By carefully regulating the concentration of the iron nitrate impregnation solution, accurate loading of Fe3O4 nanoparticles onto the carbonized hemp fiber was achieved. Due to its unique porous structure, the balance between impedance matching, and electromagnetic loss, the prepared Fe3O4 nanoparticle/carbonized hemp fiber composite exhibits light weight, high absorption strength, and broadband absorption characteristics. The broadest absorption bandwidth of 6.1 GHz can be achieved, covering the entire Ku-band, and the minimum refection loss is as low as -49.7 dB. More interestingly, the Fe3O4 nanoparticle/carbonized hemp fiber composite exhibits attractive microwave absorption performance in both the X-band and Ku-band even with a wide range of Fe3O4 nanoparticle loading. Furthermore, simulations of the radar cross section (RCS) have confirmed that the Fe3O4 nanoparticle/carbonized hemp fiber composite is effective in attenuating electromagnetic waves in a real environment. This work presents an economical and efficient method for the development of porous carbon-based absorbents.

Recycling cobalt from spent lithium-ion batteries for designing the novel cobalt nitride followers: Towards efficient overall water splitting and advanced zinc-air batteries

Although cobalt nitride (CoN)-based nanomaterials have been widely designed as advanced oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR) catalysts, the continuous consumption of lithium-ion batteries (LIBs) has led to a high price of cobalt metal. Therefore, in the future, recycling valuable Co elements from spent devices and boosting their service efficiency will inevitably promote the utilization of Co-based materials in water splitting and zinc-air batteries (ZABs). Herein, we realize the Co recycling from spent LIBs by a simple hydrometallurgy method. Under the assistance of hexamethylenetetramine and polystyrene spheres, after the hydrothermal and pyrolysis treatment in the NH3 atmosphere, the as-reclaimed cobalt oxalates were successfully transformed into novel three-dimensional (3D) CoN nanoflowers (denoted as CoN NFs). Benefiting from the unique 3D flower-like architectures, intrinsic high conductivity, large surface area, uniformly dispersed CoN nanoparticles, and the synergistic effect between Co3N and CoO phases, the 3D flower-like CoN NFs exhibited excellent OER catalytic activity. The performance was much better than commercial RuO2 in the 1.0 M KOH solution. Furthermore, the CoN NFs-based water splitting cell needed a voltage of 1.608 V to achieve the current density of 10 mA cm-2, which is even 16 mV smaller than that of Pt/C||RuO2 benchmark (1.624 V). Meanwhile, the CoN NFs-derived ZAB exhibited a high peak power density of 107.3 mW cm-2 (vs. 103.2 mW cm-2 of Pt/C-RuO2-based ZAB) and a low charge-discharge voltage gap (0.93 V vs. 1.43 V of Pt/C-RuO2-based ZAB). Due to the excellent structural and elemental stabilities, the corresponding water splitting cell and ZAB had outstanding durability. This work successfully explored an advanced industrial chain from recycling Co metal in spent devices to designing the high-efficiency HER/OER/ORR electrocatalysts for advanced water splitting devices and ZABs. This will further promote the value-added utilization of valuable Co metal in various energy storage or conversion devices.

High-performance composite elastomers with abundant heterostructures for enhanced electromagnetic wave absorption with ultrabroad bandwidth

Two-dimensional (2D) MXene has attracted vast attention in electromagnetic wave absorption (EWA), but there remains a contradiction between maintaining impedance matching and enhancing dielectric loss. Herein, the multi-scale architectures of ecoflex/2D MXene (Ti3C2Tx)@zero-dimensional CoNi sphere@one-dimensional carbon nanotube composite elastomers were successfully constructed by simple liquid-phase reduction and thermo-curing method. The binding between the hybrids as fillers and ecoflex as a matrix greatly enhanced the EWA capability of the obtained composite elastomer and improved its mechanical properties. Owing to its good impedance matching, abundant heterostructures, and synergistic electrical and magnetic losses, this elastomer exhibited an excellent minimum reflection loss of -67 dB at 9.46 GHz under a thickness of 2.98 mm. In addition, its ultrabroad effective absorption bandwidth reached 6.07 GHz. This achievement will pave the way for the exploitation of multi-dimensional heterostructures as high-performance electromagnetic absorbers with superior EWA ability.

Three-dimensional conductive network constructed by in-situ preparation of sea urchin-like NiFe2O4 in expanded graphite for efficient microwave absorption

Expanded graphite (EG) is a modified conductive lamellar carbon that has been widely studied in the field of electromagnetic wave absorption due to its low density, good electrical conductivity, and unique structure. However, its application is limited because the interlayer gap cannot match microwave wavelength, and its single composition has less microwave loss. In this study, sea urchin-like NiFe2O4/EG composites are prepared in situ between expanded graphite layers by microwave treatment. The sea urchin-like NiFe2O4 grows between the expanded graphite to form a three-dimensional conductive network structure, which enhances conductive loss of composites and further increases the interlayer distance of EG. The extended interlayer distance promotes multiple reflections and scattering of electromagnetic waves in composites and improves dielectric properties. In addition, EG with a large specific surface area provides many active sites, further promoting interface and dipole polarization. Benefiting from synergistic effect of NiFe2O4 and EG, magnetic loss and dielectric loss of NiFe2O4/EG composites have been improved and impedance matching is further enhanced. The results indicate that the minimal reflection loss of NiFe2O4/EG-4 reaches -53.47 dB at 2.69 mm, and the effective absorption bandwidth reaches 2.97 GHz. In addition, based on the computer simulation technology results, NiFe2O4/EG can attenuate microwave energy under experimental conditions. This work provides a strategy for synthesizing carbon matrix composites with adjustable dielectric parameters and electromagnetic wave properties.