Hye Ryung Byon

Non-noble-metal catalysts based on Fe–N–C moieties have shown promising oxygen reduction reaction (ORR) activity in proton exchange membrane fuel cells (PEMFCs). In this study, we report a facile method to prepare a Fe–N–C catalyst based on modified graphene (Fe–N–rGO) from heat treatment of a mixture of Fe salt, graphitic carbon nitride (g-C3N4), and chemically reduced graphene (rGO). The Fe–N–rGO catalyst was found to have pyridinic N-dominant heterocyclic N (40% atomic concentration among all

Abstract Hierarchical functionalized multiwalled carbon nanotube (MWNT)/graphene structures with thicknesses up to tens of micrometers and relatively high density (>1 g cm −3 ) are synthesized using vacuum filtration for the positive electrode of lithium batteries. These electrodes, which are self‐standing and free of binder and current collectors, utilize oxygen functional groups for Faradaic reactions in addition to double‐layer charging, which can impart high gravimetric (230 Wh kg −1 at 2

Highly sensitive single-walled carbon nanotube-field effect transistor (SWNT-FET) devices, which detect protein adsorptions and specific protein-protein interactions at 1 pM concentrations, have been achieved. The detection limit has been improved 104-fold compared to the devices fabricated by photolithography. The substantially increased sensitivity is mainly due to the increased Schottky contact area which accommodates relatively more numbers of proteins even at very low concentration. The aug

Lithium-oxygen (Li-O₂) batteries have been intensively investigated in recent decades for their utilization in electric vehicles. The intrinsic challenges arising from O₂ (electro)chemistry have been mitigated by developing various types of catalysts, porous electrode materials, and stable electrolyte solutions. At the next stage, we face the need to reform batteries by substituting pure O₂ gas with air from Earth's atmosphere. Thus, the key emerging challenges o

A cathode‐flow lithium‐iodine (Li–I) battery is proposed operating by the triiodide/iodide (I 3 − /I − ) redox couple in aqueous solution. The aqueous Li–I battery has noticeably high energy density (≈0.28 kWh kg −1 cell ) because of the considerable solubility of LiI in aqueous solution (≈8.2 m ) and reasonably high power density (≈130 mW cm −2 at a current rate of 60 mA cm −2 , 328 K). In the operation of cathode‐flow mode, the Li–I battery attains high storage capacity (≈90% of the theoretica

Organic electrodes have been extensively developed to enhance cycling performance in aqueous zinc (Zn)-ion cells. However, little is known about an ion-association process, which caused insufficient diagnoses of various cyclability results. Protons (H+) are charge carriers alongside Zn2+ ions in mildly acidic electrolyte solutions and preferentially participate in the storage process. In addition, dissociation of water can supply the additional H+, and the increased pH yields the precipitate of

A one‐pot synthesis of three‐dimensional carbon nanotube frameworks with bipyramidal sulfur particles and the application of these materials for a cathode in lithium–sulfur (Li–S) battery are reported. By simple mixing of multi‐walled carbon nanotubes (MWCNTs), sulfur powder, and capping agents in water/tetrahydrofuran, micrometer bipyramidal sulfur particles enclosed with MWCNTs are synthesized. The MWCNTs spontaneously form a 3D conducting network inside and outside the sulfur particle. Along

In lithium–oxygen (Li–O2) batteries, nanocatalysts have been widely employed as a means to suppress the large recharge overpotential and to possibly improve cyclability. However, these studies have consistently been mired with ambiguity relating to the possible exacerbation of side reactions, which in turn has brought into question the role of such catalysts in Li–O2 cells. Here, we shed light on the viability of nanocatalysts by examining the use of Ru, Pt, Pd, Co3O4, and Au nanoparticles suppo

We report a facile synthesis of Fe-N-C catalysts based on the surface functionalization of multi-walled carbon nanotubes (MWCNTs), which show high activity and stability for oxygen reduction reaction (ORR) in acid. Fe-N-MWCNT catalysts, whose ORR mass activities could vary by 3-4 times depending on the choice of Fe precursors, were found to have considerably higher ORR mass activity and higher stability than N-modified MWCNTs (N-MWCNTs). The Fe-N-MWCNT catalyst with a dominant Fe-N(x) moiety (wi

Abstract Redox‐active organometallic molecules offer a promising avenue for increasing the energy density and cycling stability of redox flow batteries. The molecular properties change dramatically as the ligands are functionalized and these variations allow for improving the solubility and controlling the redox potentials to optimize their performance when used as electrolytes. Unfortunately, it has been difficult to predict and design the stability of redox‐active molecules to enhance cyclabil

The potassium salt of <italic>N</italic>,<italic>N</italic>′-bis(glycinyl)naphthalene diimide [K₂-BNDI] showed stable two-electron redox reactions accompanied by ion-pairing in aqueous redox-flow batteries.

Abstract An aqueous lithium–iodine (Li–I 2 ) cell with solid polymer electrolyte (SPE)‐passivated metallic Li is demonstrated. The metallic Li anode is isolated from the aqueous I 3 − /I − cathode by the SPE and a Li‐ion‐conductive solid electrolyte layer. The proposed aqueous Li–I 2 cells exhibit a discharge potential of approximately 3.4 V versus Li + /Li, stable capacity retention for 50 cycles, and adequate rate capability.