VN nanoparticle-assembled hollow microspheres/N-doped carbon nanofibers: An anode material for superior potassium storage

Confining CoSe/MoSe2 Heterostructures in Interconnected Carbon Polyhedrons for Superior Potassium Storage

Metal selenides hold promise as feasible anode materials for potassium-ion batteries (PIBs), but still face problems such as poor potassium storage kinetics and dramatic volume expansion. Coupling heterostructure engineering with structural design could be an effective strategy for rapid and stable K+ storage. Herein, CoSe/MoSe2 heterojunction encapsulated in nitrogen-doped carbon polyhedron and further interconnected by three-dimensional nitrogen-doped carbon nanofibers (CoMoSe@NCP/NCFs) is ingeniously constructed. The abundant CoSe/MoSe2 heterointerfaces equipped with built-in electric fields and unique interconnected carbon polyhedrons (convenient electron/ion transfer pathway and robust mechanical buffer) promote the reaction kinetics and bolster the structural robustness. Accordingly, the CoMoSe@NCP/NCFs composite exhibits outstanding cycle life, with a capacity of 206 mAh g-1 preserved after 2500 cycles at 2 A g-1. Besides, CoMoSe@NCP/NCFs also achieves decent rate performance with 161 mAh g-1 at 10 A g-1. This research demonstrates a viable approach for constructing superior PIB anodes with both fast kinetics and high stability.

Single-atom Mn sites confined into hierarchically porous core-shell nanostructures for improved catalysis of oxygen reduction

Applications of zinc-air batteries are partially limited by the slow kinetics of oxygen reduction reaction (ORR); Thus, developing effective strategies to address the compatibility issue between performance and stability is crucial, yet it remains a significant challenge. Here, we propose an in situ gas etching-thermal assembly strategy with an in situ-grown graphene-like shell that will favor Mn anchoring. Gas etching allows for the simultaneous creation of mesopore-dominated carbon cores and ultrathin carbon layer shells adorned entirely with highly dispersed Mn-N4 single-atom sites. This approach effectively resolves the compatibility issue between activity and stability in a single step. The unique core-shell structure allows for the full exposure of active sites and effectively prevents the agglomerations and dissolution of Mn-N4 sites in cores. The corresponding half-wave potential for ORR is up to 0.875 V (vs. reversible hydrogen electrode (RHE)) in 0.1 M KOH. The gained catalyst (Mn-N@Gra-L)-assembled zinc-air battery has a high peak power density (242 mW cm-2) and a durability of ∼ 115 h. Furthermore, replacing the zinc anode achieved a stable cyclic discharge platform of ∼ 20 h at varying current densities. Forming more fully exposed and stable existing Mn-N4 sites is a governing factor for improving the electrocatalytic ORR activity, significantly cycling durability, and reversibility of zinc-air batteries.

Hybrid porous material supported in a cellulose acetate polymeric membrane for the direct immersion thin-film microextraction of parabens in water

A simple and sensitive direct immersion thin-film microextraction (DI-TFME) method based on MIL-101(Cr) modified with carbon nanofibers supported in cellulose acetate (CA-MIL-101(Cr)@CNFs) polymeric membrane was developed for the extraction and preconcentration of parabens in environmental water samples. A high-performance liquid chromatography-diode array detector (HPLC-DAD) was used for the determination and quantification of methylparaben (MP) and propylparaben (PP). The factors affecting the DI-TFME performance were investigated using central composite design (CCD). The linearity of the DI-TFME/HPLC-DAD method obtained under optimal conditions was 0.04-0.04-500 µg/L with a correlation coefficient (R2) greater than 0.99, respectively. The limits of detection (LOD) and quantification (LOQ) for methylparaben were 11 ng/L and 37 ng/L; for propylparaben, they were 13 ng/L and 43 ng/L, respectively. The enrichment factors were 93.7 and 123 for methylparaben and propylparaben. The intraday (repeatability) and interday (reproducibility) precisions expressed as relative standard deviations (%RSD) were less than 5%. Furthermore, the DI-TFME/HPLC-DAD method was validated using real water samples spiked with known concentrations of the analytes. The recoveries ranged from 91.5 to 99.8%, and intraday and interday trueness values were less than ±15%. The DI-TFME/HPLC-DAD approach was effectively used for the preconcentration and quantification of parabens in river water and wastewater samples.

3D Porous VOx/N-Doped Carbon Nanosheet Hybrids Derived from Cross-Linked Dicyandiamide-Chitosan Hydrogels for Superior Supercapacitor Electrode Materials

Three-dimensional porous carbon materials with moderate heteroatom-doping have been extensively investigated as promising electrode materials for energy storage. In this study, we fabricated a 3D cross-linked chitosan-dicyandiamide-VOSO4 hydrogel using a polymerization process. After pyrolysis at high temperature, 3D porous VOx/N-doped carbon nanosheet hybrids (3D VNCN) were obtained. The unique 3D porous skeleton, abundant doping elements, and presence of VOx 3D VNCN pyrolyzed at 800 °C (3D VNCN-800) ensured excellent electrochemical performance. The 3D VNCN-800 electrode exhibits a maximum specific capacitance of 408.1 F·g-1 at 1 A·g-1 current density and an admirable cycling stability with 96.8% capacitance retention after 5000 cycles. Moreover, an assembled symmetrical supercapacitor based on the 3D VNCN-800 electrode delivers a maximum energy density of 15.6 Wh·Kg-1 at a power density of 600 W·Kg-1. Our study demonstrates a potential guideline for the fabrication of porous carbon materials with 3D structure and abundant heteroatom-doping.