• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.627-634
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• 2023

Graphitic carbon nitride (g-C₃N₄) has attracted considerable attention since its discovery for its catalysis of water splitting to hydrogen and oxygen under visible light irradiation. However, pristine g-C₃N₄ confers only low photocatalytic efficiency and requires surface cocatalysts to reach moderate activity due to a lack of accessible surface active sites. Inspired by the high specific surface area and superior electron transfer of graphene, we developed a strongly coupled binary structure of graphene and g-C₃N₄ aerogel with 3D porous skeleton. The as-prepared 3D structure photocatalysts achieve a high surface area that favors efficient photogenerated charge separation and transfer, enhances the light-harvesting efficiency, and significantly improves the photocatalytic hydrogen evolution rate as well. The photocatalyst performance is observed to be optimized at the ratio 3:7 (g-C₃N₄:GO), leading to photocatalytic H₂ evolution of 16125.1 mmol. g^-1. h^-1 under visible light irradiation, more than 161 times higher than the rate achieved by bulk g-C₃N₄.

• Journal of Electrochemical Science and Technology
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• v.4 no.1
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• pp.41-45
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• 2013

Platinum is a well known element which shows a significant electrocatalytic activity in many important applications. In glucose sensor, because of the poisoning effect of reaction intermediates and the low surface area, the electrocatalytic activity towards the glucose oxidation is low which cause the low sensitivity. So, we fabricate a nanoporous PtZn alloy electrode by deposition-dissolution method. It provides a high active surface and a large enzyme encapsulating space per unit area when it used for an enzymatic glucose sensor. Glucose oxidase was immobilized on the electrode surface by capping with PEDOT composite and PPDA. The composite and PPDA also can exclude the interference ion such as ascorbic acid and uric acid to improve the selectivity. The surface area was determined by cyclic voltametry method and the surface structure and the element were analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray spectroscopy (EDX), respectively. The sensitivity is $13.5{\mu}A/mM\;cm^2$. It is a remarkable value with such simply prepared senor has high selectivity.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.230-235
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• 1996

The new concept of dry area formation based on Poisson distribution of active nucleation sites and the concept of the critical active site density is presented. A simple statistical model is developed to predict the change of slope of the boiling curve up to critical heat flux (CHF) quantitatively. The predictions by the present model are in good agreement with the experimental data. Also it turns out that the present model well explains the mechanism on how the surface wettability influences CHF.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.499-513
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• 2020

Among the many studies of carbon-based nanomaterials, carbon-based dots (CDs) have attracted considerable interest owing to their large surface area, intrinsic low-toxicity, excellent biocompatibility, high solubility, and low-cost with environmentally friendly routes, as well as their ability for modification with other nanomaterials. CDs have several applications in biosensing, photocatalysis, bioimaging, and nanomedicine. In addition, the fascinating electrochemical properties of CDs, including high active surface area, excellent electrical conductivity, electrocatalytic activity, high porosity, and adsorption capability, make them potential candidates for electrochemical sensing materials. This paper reviews the recent developments and synthesis of CDs and their composites for the proposed electrochemical sensing platforms. The electrochemical principles and future perspective and challenges of electrochemical biosensors are also discussed based on CDs-nanocomposites.

• Journal of the Korean Ceramic Society
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• v.55 no.1
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• pp.74-79
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• 2018

Active clay, bentonite and zeolite were used as porous materials for humidity controlling ceramic boards. The specific area and the pore volume of active clay were higher than those of bentonite and zeolite. It was effective to add white cement as well as a retarding agent to control the setting time of the ceramic paint. As the amount of added porous materials increases, the specific surface area and total pore volume of ceramic paint increase, but the average pore diameter decreases. The addition of porous materials having a high specific area and a large pore volume improves the moisture absorptive and desorptive performance of the ceramic paint. Therefore, in this experiment, the moisture absorptive and desorptive properties were best when active clay was added. Also, as the added amount of porous materials increases, the moisture absorptive and desorptive properties improve. In this experiment, when 70 mass% of active clay was added to ceramic paint, the hygroscopicity was highest at about $80g/m^2$.

• Carbon letters
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• v.12 no.3
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• pp.152-161
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• 2011

Activated carbon was prepared from pre-carbonized petroleum coke. Textural properties were determined from studies of the adsorption of nitrogen at 77 K and the surface chemistry was obtained using the Fourier-transform infrared spectrometer technique and the Boehm titration process. The adsorption of three aromatic compounds, namely phenol (P), p-nitrophenol (PNP) and benzoic acid (BA) onto APC in aqueous solution was studied in a batch system with respect to contact time, pH, initial concentration of solutes and temperature. Active carbon APC obtained was found to possess a high surface area and a predominantly microporous structure; it also had an acidic surface character. The experimental data fitted the pseudo-second-order kinetic model well; also, the intraparticle diffusion was the only controlling process in determining the adsorption of the three pollutants investigated. The adsorption data fit well with the Langmuir and Freundlich models. The uptake of the three pollutants was found to be strongly dependent on the pH value and the temperature of the solution. Most of the experiments were conducted at pH 7; the $pH_{(PZC)}$ of the active carbon under study was 5.0; the surface of the active carbon was negatively charged. The thermodynamic parameters evaluated for APC revealed that the adsorption of P was spontaneous and exothermic in nature, while PNP and BA showed no-spontaneity of the adsorption process and that process was endothermic in nature.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.04a
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• pp.309-312
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• 2004

In mountainous area with high relief, topography may cause cast shadows due to the blocking of direct solar radiation. Remote sensing images of these landscapes display reduced values of reflectance for shadowed areas compared to non-shadowed areas with similar surface cover characteristics. A variety of approaches are possible, though a common step in various active approaches is first to delineate the shadows using automated algorithm and digital surface model (or digital elevation model). This articles demonstrates a common confusion caused by cast shadows

• Korean Journal of Materials Research
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• v.30 no.5
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• pp.217-222
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• 2020

The design and fabrication of catalysts with low-cost and high electrocatalytic activity for the oxygen evolution reaction (OER) have remained challenging because of the sluggish kinetics of this reaction. The key to the pursuit of efficient electrocatalysts is to design them with high surface area and more active sites. In this work, we have successfully synthesized a highly stable and active NiCo₂S₄ nanowire array on a Ni-foam substrate (NiCo₂S₄ NW/NF) via a two-step hydrothermal synthesis approach. This NiCo₂S₄ NW/NF exhibits overpotential as low as 275 mV, delivering a current density of 20 mA cm^-2 (versus reversible hydrogen electrode) with a low Tafel slope of 89 mV dec^-1 and superior long-term stability for 20 h in 1 M KOH electrolyte. The outstanding performance is ascribed to the inherent activity of the binder-free deposited, vertically aligned nanowire structure, which provides a large number of electrochemically active surface sites, accelerating electron transfer, and simultaneously enhancing the diffusion of electrolyte.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.4
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• pp.13-23
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• 2003

Organic carbon and nitrogen contents in suspended particulate matter (SPM) and surface sediments in seawater were measured in the Northern East China Sea in summer. The distribution of particulate organic carbon(POC) and particulate organic nitrogen(PON) were in the ranges of 54~481㎍/ℓ and 6~85㎍/ℓ, respectively, with relatively high level of concentrations in the western and southern sides of the study area. Also, there has been a significantly positive correlation between POC and PON, gradually increasing toward the deeper range of depth. Average C:N ratios of POC and PON of SPM were 6 in study area. The ratios of POC to PON of SPM increased as the range of depth increased, indicating nitrogen decomposes more rapidly than carbon and is considered to be influenced by the input of detritus from surface sediments. The distribution of total organic matter(TOM), total organic carbon(TOC) and total organic nitrogen(TON) in surface sediments were in the ranges of 3.1~9.6%, 0.282~0.635% and 0.022~0.069%, respectively, with relatively low range in the western and northern sides of the study area. The ratio of TOC to TON of surface sediments were in the range of 9.8~17.4(average of 13), strongly indicating the active role of the input from the terrestrial organic pollutants.

• Composites Research
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• v.29 no.4
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• pp.132-137
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• 2016

Based on mussel-inspired polydopamine (PDA), a novel technique to fabricate carbon nanowire (CNW) arrays is presented for a possible use of porous carbon electrode in electrochemical energy storage applications. PDA can give more porosity and nitrogen-doping effect to carbon electrodes, since it has high graphitic carbon yield characteristic and rich amine functionalities. Using such outstanding properties, the applicability of PDA for electrochemical energy storage devices was investigated. To achieve this, the decoration of the CNW arrays on carbon fiber surface was performed to increase the surface area for storage of electrical charge and the chemical active sites. Here, zinc oxide (ZnO) nanowire (NW) arrays were hydrothermally grown on the carbon fiber surface and then, PDA was coated on ZnO NWs. Finally, high temperature annealing was performed to carbonize PDA coating layers. For higher energy density, manganese oxide ($MnO_x$) nanoparticles (NPs), were deposited on the carbonized PDA NW arrays. The enlarged surface area induced by carbon nanowire arrays led to a 4.7-fold enhancement in areal capacitance compared to that of bare carbon fibers. The capacitance of nanowire-decorated electrodes reached up to $105.7mF/cm^2$, which is 59 times higher than that of pristine carbon fibers.