Jeung Ku Kang

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

The high porosity of metal-organic frameworks (MOFs) has been used to achieve exceptional gas adsorptive properties but as yet remains largely unexplored for electrochemical energy storage devices. This study shows that MOFs made as nanocrystals (nMOFs) can be doped with graphene and successfully incorporated into devices to function as supercapacitors. A series of 23 different nMOFs with multiple organic functionalities and metal ions, differing pore sizes and shapes, discrete and infinite meta

The increasing demands on high performance energy storage systems have raised a new class of devices, so-called lithium ion capacitors (LICs). As its name says, LIC is an intermediate system between lithium ion batteries and supercapacitors, designed for taking advantages of both types of energy storage systems. Herein, as a quest to improve the Li storage capability compared to that of other existing carbon nanomaterials, we have developed extrinsically defective multiwall carbon nanotubes by n

Postsynthetic exchange (PSE) of Ti(IV) into a Zr(IV)-based MOF enabled photocatalytic CO2 reduction to HCOOH under visible light irradiation with the aid of BNAH and TEOA. Use of a mixed-ligand strategy enhanced the photocatalytic activity of the MOF by introducing new energy levels in the band structure of the MOF.

Generally, crystals of synthetic porous materials such as metal-organic frameworks (MOFs) are commonly made up from one kind of repeating pore structure which predominates the whole material. Surprisingly, little is known about how to introduce heterogeneously arranged pores within a crystal of homogeneous pores without losing the crystalline nature of the material. Here, we outline a strategy for producing crystals of MOF-5 in which a system of meso- and macropores either permeates the whole cr

Highly efficient electrochemical nitrate reduction could be key for sustainable ammonia production. Our NiFe LDH/Cu foam electrode exhibits an NH 3 selectivity of 95.8% with 98.5% nitrate conversion.

We present a new hybrid density-functional method which predicts transition state barriers with the same accuracy as CBS-APNO, and transition state barriers and enthalpies of reaction with smaller errors than B3LYP, BHandHLYP, and G2. The accuracy of the new method is demonstrated on 132 energies, including 74 transition state barriers and 58 enthalpies of reaction. For 40 reactions with reliable experimental barriers, the absolute mean deviations of the transition state barriers are 0.9, 1.0, 3

Vanadium pentoxide (V2O5) has received considerable attention as a lithium battery cathode because its specific capacity (>250 mA h g−1) is higher than those (<170 mA h g−1) of most commercial cathode materials. Despite this conspicuous advantage, V2O5 has suffered from limited cycle life, typically below a couple of hundred cycles due to the agglomeration of its particles. Once V2O5 particles are agglomerated, the insulating phases continuously expand to an extent that ionic and electronic cond

Here, we have synthesized the new titanium-embedded layered double hydroxides (LDHs), such as (Ni/Ti)LDH and (Cu/Ti)LDH. First of all, the formation of LDH structures and the bonding nature for a mixed oxide structure of LDHs are explored in this work. Also, it is determined that our LDHs show two absorption bands in the red and blue regions under visible light, thus different from those of a pure titanium oxide with absorption bands in only the UV region. We find that the (Ni/Ti)LDH with the hi

Quantum chemistry is used to investigate the HF/H2O chemical etching mechanism of silicon dioxide. Etching proceeds through four sequential steps to remove silicon as SiF4(g) for silicon dioxide, eventually leading to a fluorine-terminated silicon surface which HF attacks, resulting in a hydrogen-passivated silicon surface. Our predicted activation barriers show that the concerted attack by HF and H2O enhances the etch rate over etching by HF alone by reducing the barrier for each etching step.

Highly porous gallium oxide was synthesized by reconstructing its surface and body with mesopores and macropores. For the first time, the efficient photocatalytic conversion of CO2 into a high energy carrier, CH4, using the porous gallium oxide was realized without any co-particle or sacrificial reagent. The enhanced photocatalytic activity is mainly attributed to the 300% higher CO2 adsorption capacity, as well as the 200% increased surface area, compared to the bulk nanoparticles. Furthermore,

Metal-organic frameworks (MOFs) with isolated metal-monocatecholato groups have been synthesized via postsynthetic exchange (PSE) for CO2 reduction photocatalyst under visible light irradiation in the presence of 1-benzyl-1,4-dihydronicotinamide and triethanolamine. The Cr-monocatecholato species are more efficient than the Ga-monocatecholato species.

We report electrochemical performance of a TiO₂ combined with a nitrogen-doped open channeled graphene anode composite for sodium ion batteries.

Metal-organic frameworks (MOFs) have recently received much attention as promising candidates for gas storage, chemical separation, and heterogeneous catalysis. However, the applicability of MOFs remains limited due to their relatively large band gaps. Here, on the basis of first-principles theory study, it is demonstrated that this problem could be overcome by tailoring Zn2+ ions in MOFs with Co2+ ions while maintaining the same organic linkers. Density of states and molecular orbitals for MOFs

Nickel oxide-encapsulated hollow carbon nitride spheres with multiporosity show an ∼250% enhancement in capacitance, in addition to their robust cycle life.