• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.29-32
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• 2008

The cell performance of direct formic acid fuel cell (DFAFC) having catalysts coated by electrospray was analyzed. Pd catalyst was used for the anode electrode and Pd catalyst loading amount and formic acid feed rate dependances of fuel cell performance were evaluated. When loading amount of Pd is in between 3mg/$cm^2$ and 7mg/$cm^2$ and formic acid feed rate is 5ml/min., 3mg/$cm^2$ sample showed better potential at 129 mA/$cm^2$ and power density due to difference in mass transfer limitation. However, when the feed rate is greater than 10ml/min., the opposite tendency was observed between 3mg/$cm^2$ and 7mg/$cm^2$ samples. The result was attributed to improvement in electrochemical reaction of the Pd. Based on the above results, In DFAFC including Pd catalyst that was coated by electrospray, 0.537V as the maximum potential at 129 mA/$cm^2$ was attained.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.702-707
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• 2012

During the last few decades, toxic chemicals used in various industries have caused global pollution and the side products such as carbon dioxide and methane gas have contributed to global warming. Thus, it is desirable to develop new alternative solvents. It is well known that ionic liquids display a variety of environmentally friendly physical properties: nonvolatile, nonflammable, wide electrochemical windows, high inherent conductivities, wide thermal operating ranges, chemically inert, and limited miscibilities with organic solvents. Because of these characteristics, ionic liquids are promising candidates as solvents for synthetic chemistries, catalysis, and gas separations. In this study, we synthesized morpholiunium salts as N-ethyl-N-methylmorpholine Bromide, N-butyl-N-methylmorpholine Bromide, N-octyl-N-methylmorpholine Bromide, N-ethyl-N-methylmorpholine Tetrafluoroborate, N-butyl-N-methylmorpholine Tetrafluoroborate, N-octyl-N-methylmorpholine Tetrafluoroborate, N-ethyl-N-methylmorpholine Hexafluorophosphate, N-butyl-N-methylmorpholine Hexafluorophosphate, and N-octyl-N-methylmorpholine Hexafluorophosphate. The melting points, decomposition temperatures and electrochemical stabilities of the salts were measured by DSC, TGA, and CV, respectively. The salts with halide anion showed high melting points ($150{\sim}200^{\circ}C$), low decomposition temperatures ($200{\sim}230^{\circ}C$), narrow electrochemical stabilities (3.4~3.6 V). The synthesized salts with inorganic anions, on the other hand, presented low melting point ($50{\sim}110^{\circ}C$), high decomposition temperatures ($250{\sim}380^{\circ}C$), wide electrochemical stabilities (6.1~6.3 V). We also found that the properties depend on the length of the carbon chain.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.8
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• pp.823-830
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• 2008

The feasibility study for the application of the photoelectrocatalytic decolorization of Rhodamine B(RhB) was performed in the slurry photoelectrochemical reactor with powder TiO$_2$. The photoelectrocatalytic process was consisted of powder TiO$_2$, Pt electrode and three 8 W UV-C lamps. The effects of operating conditions, such as current, electrolyte, air flow rate and electrode material were evaluated. The experimental results showed that optimum TiO$_2$ dosage and current in photoelectrocatalytic process were 0.4 g/L and 0.02 A, respectively. It was found that the RhB could be degraded more efficiently by this photoelectrocatalytic process than the sum of the two individual oxidation processes(photocatalytic and electrolytic process). It demonstrated a synergetic effect between the photo- and electrochemical catalysis. Photoelectrocatalytic process was affected to air flow rate and optimum air flow rate was 2 L/min. The electrode material and NaCl effect of decolorization of RhB were not significant within the experiment conditions.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.35-38
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• 2014

Herein, we report on the preparation of red fluorescent Si nanoparticles stabilized with styrene. Nano-sized Si particles emit fluorescence under UV excitation, which could be used to open up new applications in the fields of optics and semi-conductor research. Unfortunately, conventional methods for the preparation of red fluorescent Si nanoparticles suffer from the lack of a fully-established standard synthesis protocol. A common initial approach during the preparation of semi-conductors is the etching of crystalline Si wafers in a HF/ethanol/$H_2O$ bath, which provides a uniformly-etched surface of nanopores amenable for further nano-sized modifications via tuning of various parameters. Subsequent sonication of the etched surface crumbles the pores on the wafer, resulting in the dispersion of particles into the solution. In this study, we use styrene to occupy these platforms to stabilize the surface. We determine that the liberated silicon particles in ethanol solution interact with styrene, resulting in the substitution of Si-H bonds with those of Si-C as determined via UV photo-catalysis. The synthesized styrene-coated Si nanoparticles exhibit a stable, bright, red fluorescence under excitation with a 365 nm UV light, and yield approximately 100 mg per wafer with a synthesis time of 2 h. We believe this protocol could be further expanded as a cost-effective and high-throughput standard method in the preparation of red fluorescent Si nanoparticles.

• Clean Technology
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• v.28 no.2
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• pp.97-102
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• 2022

Lithium sulfur (Li-S) batteries have attracted considerable attention as a promising candidate for next-generation power sources due to their high theoretical energy density, low cost, and eco-friendliness. However, the poor electrical conductivity of sulfur and its insoluble discharging products (Li₂S₂/Li₂S), large volume changes, severe self-discharge, and dissolution of lithium polysulfide intermediates result in rapid capacity fading, low Coulombic efficiency, and safety risks, hindering Li-S battery commercial development. In this study, a three-dimensionally (3D) connected hierarchical porous carbon framework (HPCF) derived from waste sunflower seed shells was synthesized as a sulfur host for Li-S batteries via a chemical activation method. The natural 3D connected structure of the HPCF, originating from the raw material, can effectively enhance the conductivity and accessibility of the electrolyte, accelerating the Li⁺/electron transfer. Additionally, the generated micropores of the HPCF, originated from the chemical activation process, can prevent polysulfide dissolution due to the limited space, thereby improving the electrochemical performance and cycling stability. The HPCF/S cell shows a superior capacity retention of 540 mA h g^-1 after 70 cycles at 0.1 C, and an excellent cycling stability at 2 C for 700 cycles. This study provides a potential biomass-derived material for low-cost long-life Li-S batteries.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.443-455
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• 2013

Electrochemical studies on charge transfer reactions across the interface between two immiscible electrolyte solutions (ITIES) have greatly attracted researcher's attentions due to their wide applicability in research fields such as ion sensing and biosensing, modeling of biomembranes, pharmacokinetics, phase-transfer catalysis, fuel generation and solar energy conversion. In particular, there have been extensive efforts made on developing sensing platforms for ionic species and biomolecules via gelifying one of the liquid phases to improve mechanical stability in addition to creating microscale interfaces to reduce ohmic loss. In this review, we will mainly discuss on the basic principles, applications and future aspects of various sensing platforms utilizing ion transfer reactions across the ITIES. The ITIES is classified into four types : (i) a conventional liquid/liquid interface, (ii) a micropipette supported liquid/liquid interface, (iii) a single microhole or an array of microholes supported liquid/ liquid interface on a thin polymer film, and (iv) a microhole array liquid/liquid interface on a silicon membrane. Research efforts on developing ion selective sensors for water pollutants as well as biomolecule sensors will be highlighted based on the use of direct and assisted ion transfer reactions across these different ITIES configurations.

• Journal of the Korean Electrochemical Society
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• v.2 no.1
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• pp.31-37
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• 1999

Copper-containig enzyme, laccase (Rhus vernicifera) was immobilized onto gold electrode using self-assembly technique and its surface properties and catalytic activities were examined. Laccase is an oxidoreductase capable to oxidize diphenols or diamines by 4-electron reduction of molecular oxygen without superoxide or peroxide intermediates. The electrode surface were modified by $\beta-mercaptopropionate$ to have a net negative charge in neutral solution and positively charged laccase (pI=9) was immobilized by electrostatic interaction. The successful immobilization was confirmed by cyclic voltammograms which showed typical surface-confined shapes and behaviors. The amount of charge to reduce the surface was similar to the charge calculated assuming the surface being covered by monolayer. The activity of the immobilized enzyme was tested by the capbility of oxidizing a substrate, ABTS (2,2-azine-bis-(3-ethylbenzthioline-6-sulfonic acid) and it was maintained for $2\~3$ days at $4^{\circ}C$. The immobilzed laccase showed about $10\~15\%$ activity compared to that in solution. The laccase-modified electrode showed the activity of elefoocatalytic reduction of oxygen in the presence of mediator, $Fe(CN)_6^{3-}$ The addtion of azide which is an inhibitor of laccase compeletly eliminated the catalytic current.