Jiseop Oh

A sensitive electrochemical sensor using an iron oxide/graphene composite for the simultaneous detection of heavy metal ions

We report an analytical assessment of an iron oxide (Fe2O3)/graphene (G) nanocomposite electrode used in combination with in situ plated bismuth (Bi) working as an electrochemical sensor for the determination of trace Zn(2+), Cd(2+), and Pb(2+). The as-synthesized nanocomposites were characterized by transmission electron microscopy, scanning electron microscopy, thermo-gravimetric analyzer, and X-ray diffraction. The electrochemical properties of the Fe2O3/G/Bi composite modified electrode were investigated. Differential pulse anodic stripping voltammetry was applied for the detection of metal ions. Due to the synergetic effect between graphene and the Fe2O3 nanoparticles, the modified electrode showed improved electrochemical catalytic activity high sensitivity toward trace heavy metal ions. Several parameters such as the preconcentration potential, bismuth concentration, preconcentration time, and pH were carefully optimized to determine the target metal ions. Under optimized conditions, the linear range of the electrode was 1-100μgL(-1) for Zn(2+), Cd(2+), and Pb(2+), and the detection limits were 0.11μgL(-1), 0.08μgL(-1), and 0.07μgL(-1), respectively (S/N =3). Repeatability (% RSD) was found to be 1.68% for Zn(2+), 0.92% for Cd(2+), and 1.69% for Pb(2+) for single sensor with 10 measurements and 0.89% for Zn(2+), 1.15% for Cd(2+), and 0.91% for Pb(2+) for 5 different electrodes. The Fe2O3/G/Bi composite electrode was successfully applied to the analysis of trace metal ions in real samples. The solventless thermal decomposition method applied to the simple and easy synthesis of nanocomposite electrode materials can be extended to the synthesis of nanocomposites and promising electrode materials for the determination of heavy metal ions.

Multi-Heteroatom-Doped Hollow Carbon Attached on Graphene Using LiFePO4 Nanoparticles as Hard Templates for High-Performance Lithium–Sulfur Batteries

P, O, and N heteroatom-doped hollow carbon on graphene (PONHC/G) from nanosized LiFePO4 (LFP) as a hard template is shown to be a very efficient sulfur host for lithium-sulfur (Li-S) batteries. The PONHC/G made from LFP nanoparticles as hard materials provides sufficient voids with various pore sizes for sulfur storage, and doping of the carbon structures with various heteroatoms minimized dissolution/diffusion of the polysulfides. The obtained PONHC/G can store sulfur and mitigate diffusion of the dissolved polysulfide owing to the well-organized host structure and the strong chemical affinity for polysulfides because of the polarization effect of the heteroatom dopants. As a cathode, S@PONHC/G shows excellent cycle stability and rate capability, as confirmed by polysulfide adsorption analysis. Therefore, PONHC/G may show high potential as a sulfur scaffold in the commercialization of Li-S batteries through additional modification and optimization of these host materials.