Min Yeong Song

Citrus-Peel-Derived, Nanoporous Carbon Nanosheets Containing Redox-Active Heteroatoms for Sodium-Ion Storage

Advanced design of nanostructured functional carbon materials for use in sustainable energy storage systems suffers from complex fabrication procedures and the use of special methods and/or expensive precursors, limiting their practical applications. In this study, nanoporous carbon nanosheets (NP-CNSs) containing numerous redox-active heteroatoms (C/O and C/N ratios of 5.5 and 34.3, respectively) were fabricated from citrus peels by simply heating the peels in the presence of potassium ions. The NP-CNSs had a 2D-like morphology with a high aspect ratio of >100, high specific surface area of 1167 m(2) g(-1), and a large amount of nanopores between 1 and 5 nm. The NP-CNSs also had an electrical conductivity of 2.6 × 10(1) s cm(-1), which is approximately 50 times higher than that of reduced graphene oxide. These unique material properties resulted in superior electrochemical performance with a high specific capacity of 140 mAh g(-1) in the cathodic potential range. In addition, symmetric full-cell devices based on the NP-CNSs showed excellent cyclic performance over 100,000 repetitive cycles.

Long-Lasting Nb2O5-Based Nanocomposite Materials for Li-Ion Storage

Advanced nanostructured hybrid materials can help us overcome the electrochemical performance limitations of current energy storage devices. In this study, three-dimensional porous carbon nanowebs (3D-CNWs) with numerous included orthorhombic Nb2O5 (T-Nb2O5) nanoparticles were fabricated using a microbe-derived nanostructure. The 3D-CNW/T-Nb2O5 nanocomposites showed an exceptionally stable long-term cycling performance over 70 000 cycles, a high reversible capacity of ∼125 mA h g-1, and fast Li-ion storage kinetics in a coin-type two-electrode system using Li metal. In addition, energy storage devices based on the above nanocomposites achieved a high specific energy of ∼80 W h kg-1 together with a high specific power of ∼5300 W kg-1 and outstanding cycling performance with ∼80% capacitance retention after 35 000 cycles.

Dispersion stability of chemically reduced graphene oxide nanoribbons in organic solvents

In this study, the dispersion stability of graphene oxide nanoribbons (GONRs) and chemically reduced GONRs (CR-GONRs) in various organic solvents was investigated. Homogeneous colloidal suspensions of GONRs were obtained in hydrophilic solvents such as water, N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP). After chemical reduction, amphiphilic dispersion behaviour of CR-GONRs was observed over a wide range of solvents including water, methanol, ethanol, DMF, NMP, acetone, styrene, and xylene. In contrast, the dispersion stability of CR-GONRs was poor in ambiguously hydrophilic or hydrophobic solvents such as tetrahydrofuran, methyl methacrylate, and chloroform.

Morphologies and surface properties of cellulose-based activated carbon nanoplates

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