Schematic of the NiCu(CO₃)(OH)₂, NiZn(CO₃)(OH)₂, and Ni_xCu_yZn_z(CO₃)(OH)₂ compounds prepared on a Ni foam substrate.

A schematic of (a) a NiCo(CO₃)(OH)₂ compound fabricated with Ni foam and (b) a NiCo(CO₃)(OH)₂ compound synthesized without a Ni foam substrate.

Microplastic pollution represents a significant global environmental issue, with cigarette filters being a major contributor due to their slow biodegradation. To address this issue while creating valuable materials, we developed a novel approach to synthesize nitrogen-doped carbon nanotubes on carbonized cigarette filter powder (NCNT@cCFP) using a microwave irradiation and nickel-catalyzed process. The successful incorporation of nitrogen (~6.6 at.%) and the enhanced graphitic structure create a hierarchical conductive network with abundant active sites for electrochemical reactions. The resulting NCNT@cCFP electrode exhibits a specific capacitance of 452 F/g at 1 A/g in a three-electrode configuration. The integrated hierarchical structure facilitates efficient electron transport and ion diffusion, leading to excellent rate capability (91.6% at 10 A/g) and cycling stability (96.5% retention after 5000 cycles). Furthermore, a symmetric supercapacitor device demonstrates promising energy storage capability with a maximum energy density of 14.0 Wh/kg at 483.1 W/kg, while maintaining 10.4 Wh/kg at a high power density of 4419.1 W/kg. This synergistic waste recycling strategy combined with microwave-driven synthesis offers a sustainable pathway for developing high-performance energy storage materials.

Two-dimensional (2D) metallic transition metal dichalcogenides (TMDCs) have attracted extensive interest in various fields owing to their unique electronic properties. However, studies on their transport properties and the modulation of these properties based on their band structure are limited. Herein, we studied the transport phenomena in 2D metallic 2H-NbSe₂ using experimental and theoretical approaches. The transport properties, including electrical conductivity (σ) and Seebeck coefficient (S), of mechanically exfoliated 2H-NbSe₂ nanosheets were measured. We observed field effect-dependent variations in σ and S of the 2H-NbSe₂ nanosheets. Theoretical calculations of the electronic band structures and estimations of the transport properties of 2D 2H-NbSe₂ crystals were conducted to verify and explain the experimental results. The superconducting transition temperature of the exfoliated NbSe₂ nanosheets validated the reliability of the sample preparation procedures and indicated the high quality of the samples. Our findings provide a basis for understanding the electrical properties of metallic TMDCs intended for various applications.