There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Recent years have witnessed many breakthroughs in research on graphene (the first two-dimensional atomic crystal) as well as a significant advance in the mass production of this material. This one-atom-thick fabric of carbon uniquely combines extreme mechanical strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.

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A roadmap for graphene

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

A noble-metal-free electrocatalyst comprised of hybrid Ni2P−MnP nanosheet coupled with Co2P nanoflowers (Ni2P−[email protected]2P) reinforced on nickel foam has been achieved with a unique heterostructure architecture for highly competent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Tri-phased Ni2P−[email protected]2P nanocrystal offers tremendously active and robust electrocatalytic efficacy heralded by low HER (60 mV) and OER (255 mV) to achieve (10 and 30) mA cm−2 current densities, respectively. The outstanding electrochemical performance is due to the distinctive architectural feature, high surface area with optimum porosity, bountiful Ni2P−MnP and Co2P heterointerface interaction, and synergism among Ni2P, MnP, and Co2P multi-active sites. The Ni2P−[email protected]2P (+,−) alkaline electrolyzer delivers a low cell voltage of 1.50 V at a current density of 10 mA cm−2, along with astonishing long-term robustness. Moreover, the electrocatalyst displays a Faradaic yield of around (97.2 and 97.9) % at 50 mA cm−2 for H2 and O2 respectively. This work is expected to pave the way for novel insights into the fabrication of efficient electrocatalysts for practical water-splitting applications. 

Unique heterointerface engineering of Ni2P−MnP nanosheets coupled Co2P nanoflowers as hierarchical dual-functional electrocatalyst for highly proficient overall water-splitting

Transition-metal-based layered triple hydroxides (LTHs) are evolving as potential positrode candidates for high-performance supercapacitors; however, their phase stabilization is still critical. Alongside, the availability of limited negatrodes pushes research toward exploring novel alternatives in order to minimize performance limitation issues in the fabricated supercapacitors. Herein, a facile strategy for stabilizing freestanding MnCuCo-LTH-based positrode possessing intermingled nanodisk-needle-like morphology is reported. Alongside, novel high-surface-area negatrodes based on Mn1Fe2S2 exhibiting porous microthorn-like morphology are also optimized. MnCuCo_LTH and Mn1Fe2S2 exhibit remarkably high specific capacities of ∼494 mAh g-1 (∼2540 F g-1) and ∼429 mAh g-1 (∼1546 F g-1), respectively, at 1 A g-1. The fabricated quasi-solid-state supercapacitor equipped with a poly(vinyl alcohol) (PVA)-KOH gel electrolyte displays a high specific capacity of ∼144 mAh g-1 and a specific capacitance of ∼325 F g-1 at 1 A g-1. The ultrahigh energy cum power traits of ∼105 Wh kg-1 (1 A g-1) and ∼8370 W kg-1 (at 10 A g-1) establish an asymmetric supercapacitor as a high-performance energy storage device. This device shows an appreciably high cycling life with a capacitance retention of ∼93% after 10 000 consecutive cycles, at 10 A g-1. This approach provides a neoteric foresight for developing high-performance advanced energy storage devices equipped with cheaper and eco-friendly components.

Freestanding Binder-Free Electrodes with Nanodisk-Needle-like MnCuCo-LTH and Mn1Fe2S2 Porous Microthorns for High-Performance Quasi-Solid-State Supercapacitors.

Single Platinum Atoms Implanted 2D Lateral Anion-Intercalated Metal Hydroxides of Ni2(OH)2(NO3)2 as Efficient Catalyst for High-yield Water Splitting

Rechargeable zinc-air batteries (ZABs) are promising energy storage systems due to their low-cost and safety. However, the working principle of ZABs is based on oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which display sluggish kinetic and low stability. Herein, this work proposes a novel method to design a heterogeneous CoP/CoO electrocatalyst on mesopore nanobox carbon/carbon nanotube (CoP/CoO@MNC-CNT) that enriched active sites and synergistic effect. Moreover, the well-defined heterointerfaces could lower the energy barrier for intermediate species adsorption and promote OER and ORR electrochemical performances. The CoP/CoO@MNC-CNT electrocatalyst presents a high half-wave potential of 0.838 V for ORR and a small overpotential of 270 mV for OER. The ZABs-based CoP/CoO@MNC-CNT air-cathode shows an open-circuit voltage of 1.409 V, the long-term cycle life of 500 h with a small voltage difference change of 7.7%. Additionally, the flexible ZABs exhibit highly mechanical stability, demonstrating their application potential in wearable electronic devices.

Tailored Heterojunction Active Sites for Oxygen Electrocatalyst Promotion in Zinc-Air Batteries.

In an attempt to find an alternative approach to reduce the use of noble metal-based electrocatalysts, a new hybrid nanostructure based on molybdenum-iron nitride nanoparticles (Mo–Fe–N NPs) deposited carbon nanotubes (CNTs) supported on nickel foam substrate is fabricated via a facile synthetic approach. Highly uniform and dense Mo–Fe–N NPs achieves full coverage on surface of the CNTs with good interactions and enhanced hetero-charge transfer, thus leading to improvements in both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The fabricated hybrid shows small overpotential of 106 mV at 10 mA cm−2 for HER and 420 mV at 100 mA cm−2 for OER, along with prospective stability after 20 h of continuous testing in alkaline electrolyte (1.0 M KOH). The catalytic activities of the Mo–Fe–N/CNTs material are shown to be superior to those of other synthesized catalysts as well as of commercial Pt/C and RuO2 catalysts. These results may pave a potential route to the fabrication of novel electrocatalysts having high performance that can effectively replace precious metal-based catalysts in electrochemical water splitting technology.

Nam Hoon Kim

Papers

Unique heterointerface engineering of Ni2P−MnP nanosheets coupled Co2P nanoflowers as hierarchical dual-functional electrocatalyst for highly proficient overall water-splitting

Freestanding Binder-Free Electrodes with Nanodisk-Needle-like MnCuCo-LTH and Mn1Fe2S2 Porous Microthorns for High-Performance Quasi-Solid-State Supercapacitors.

Single Platinum Atoms Implanted 2D Lateral Anion-Intercalated Metal Hydroxides of Ni2(OH)2(NO3)2 as Efficient Catalyst for High-yield Water Splitting

Tailored Heterojunction Active Sites for Oxygen Electrocatalyst Promotion in Zinc-Air Batteries.

Ultrasmall molybdenum-iron nitride nanoparticles confined carbon nanotubes hybrids for efficient overall water splitting