Hyungmo Jeong

Although various carbon nanomaterials including activated carbon, carbon nanotubes, and graphene have been successfully demonstrated for high-performance ultracapacitors, their capacitances need to be improved further for wider and more challenging applications. Herein, using nitrogen-doped graphene produced by a simple plasma process, we developed ultracapacitors whose capacitances (∼280 F/g(electrode)) are about 4 times larger than those of pristine graphene based counterparts without sacrific

Due to its excellent capacity, around 4000 mA h g−1, silicon has been recognized as one of the most promising lithium-ion battery anodes, especially for future large-scale applications including electrical vehicles and utility power grids. Nevertheless, Si suffers from a short cycle life as well as limitations for scalable electrode fabrication. Herein, we report a novel design for highly robust and scalable Si anodes: Si nanoparticles embedded in porous nitrogen-doped carbon spheres (NCSs). The

Abstract Copper (Cu) offers a means for producing value‐added fuels through the electrochemical reduction of carbon dioxide (CO 2 ), i.e., the CO 2 reduction reaction (CO 2 RR), but designing Cu catalysts with significant Faradaic efficiency to C 2+ products remains as a great challenge. This work demonstrates that the high activity and selectivity of Cu to C 2+ products can be achieved by atomic‐scale spacings between two facets of Cu particles. These spacings are created by lithiating CuO x pa

Abstract Electrochemical carbon dioxide reduction reaction (CO 2 RR) is a promising approach to mitigate CO 2 concentration and generate carbon feedstock. Recently, the (sub‐)nanometer design of catalyst structures has been revealed as an efficient means to control the reaction process through the local reaction environment. Herein, the synthesis of a novel tin oxide (SnO x ) nanoparticle (NP) catalyst with highly controlled sub‐nanoscale interplanar gaps of widths <1 nm (SnO x NP‐s) is repor

Nanocrystals are promising structures, but they are too large for achieving maximum energy storage performance. We show that rescaling 3-nm particles through lithiation followed by delithiation leads to high-performance energy storage by realizing high capacitance close to the theoretical capacitance available via ion-to-atom redox reactions. Reactive force-field (ReaxFF) molecular dynamics simulations support the conclusion that Li atoms react with nickel oxide nanocrystals (NiO-n) to form lith

Abstract All‐solid‐state battery (ASSB) technology is the focus of considerable interest owing to their safety and the fact that their high energy density meets the requirements of emerging battery applications, such as electric vehicles and energy storage systems (ESSs). In light of this, current research on high‐energy ASSBs harnesses the benefits of solid‐state battery systems by employing anode materials with high energy densities. Owing to the excellent physical safety of solid electrolytes

Abstract Aqueous electrochemical energy storages are of enormous attention due to their high safety and being environmentally friendly, but they must satisfy very challenging standards in energy and power densities over long repeated charging/discharging cycles. Herein, a strategy to realize high‐performance aqueous hybrid capacitors (AHCs) using pseudocapacitive negative and positive electrodes is reported. Polymer chains, which are synthesized by in situ polymerization of polyaniline on reduce

Abstract Realization of safe electrochemical energy storages with high energy density and long cycle life along with the high power density enabling fast charging is a major challenge. Here, a strategy to realize high‐performance aqueous energy storages using porous Mn 3 O 4 (p‐MG) positive and porous Fe 2 O 3 (p‐FG) negative electrodes, where granular nanoclusters composing nanoparticles are produced on graphene through lithiation‐induced conversion and the shortened ion diffusion lengths in p‐

A popular substance in the MXene family, titanium carbide (Ti3C2Tx), has received substantial attention mainly due to its high metallic conductivity, easy solution processability, and environment friendliness. However, the poor oxygen resistance nature of MXene has prevented its practical applications from being realized. Despite significant attempts to improve the oxidative stability of MXenes, a comprehensive understanding of the oxidation mechanism is still elusive, thus leaving an optimal st

We report that ammonia borane with a high uptake capacity for hydrogen can be encapsulated in a metal-organic framework (MOF) via capillary action, where the MOF functions as a chemical guide to control the hydrogen desorption pathways of ammonia borane by releasing only pure hydrogen, lowering its hydrogen desorption temperature, and suppressing its volumetric expansion during hydrogen desorption.