• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.256-257
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• 2005

We fabricated self-assembled monolayers(SAMs) onto quartz crystal microbalance(QCM) using viologen, which has been widely used as electron acceptor and electron transfer mediator. The viologen derivative exist in three redox states, namely. These redox reactions are highly reversible and can be cycled many times without significant side reactions, respectively. We studied the characteristics of charge transfer using different electrolyte solutions by electrochemical quartz crystal microbalance (EQCM). From the data, the redox peak currents were nearly equal charges during redox reaction and existed to an excellent linear interrelation between the scan rates and first redox peak currents. The redox reactions of viologen were highly reversible and the EQCM has been employed to monitor the electrochemically induced adsorption of SAMs during the redox reactions.

• Journal of the Korean Chemical Society
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• v.39 no.4
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• pp.294-300
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• 1995

The photoelectrochemical behavior of polypyrrole films on Pt, glassy-C and indium tin oxide(ITO) under illumination was studied in aqueous solution containing a redox couple such as I-/I2 or Fe(CN)64-/Fe(CN)63-. Polypyrrole(PPy) was coated on Pt, glassy-C and ITO electrodes using electrochemical polymerization of pyrrole by potentiostatic method. Illumination of the PPy film results in the increase of cathodic and anodic currents at redox potentials of the redox species. These enhanced currents are caused both by the semiconductor characteristics of PPy and by the photothermal acceleration of redox reaction at PPy-electrode surface, and are dependent on the pH of redox solutions and the dopants in PPy.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.3
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• pp.340-348
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• 2011

Effects of various inorganic-metal oxide (Zr, Zn, Si, Al and Ca as promoters and stabilizers) additive on the reduction rate of iron oxide and the composition of forming hydrogen using the steam-iron cycle operation was investigated. The reduction rate of redox agent with additive was determined from weight change by TGA. The changes of weight loss and reduction rate according to redox agent with various additive affected the hydrogen purity and cycle stability of the process. The cyclic micro reactor showed that hydrogen purity exceeding 95% could be obtained by the water splitting with Si/Fe, Zn/Fe, Zr/Fe redox agents. The redox agents with these elements had an affect on redox cycle stability as a good stabilizer for forming hydrogen by the steam-iron process.

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.176-183
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• 2008

Redox complexes to transport electrodes from bioreactors to electrodes are very important part in electrochemical biosensor industry. A novel osmium redox complexes were synthesized by the coordinating pyridine group having different functional group at 4-position with osmium metal. Newly synthesized osmium complexes are described as ${[Os(dme-bpy)}_2{(ap-im)Cl]}^{+/2+}$, ${[Os(dme-bpy)}_2{(ap-im)Cl]}^{+/2+}$, ${[Os(dmo-bpy)}_2{(ap-im)Cl]}^{+/2+}$, ${[Os(dcl-bpy)}_2{(ap-im)Cl]}^{+/2+}$. We have been studied the electrochemical characteristics of these osmium complex with electrochemical techniques such as cyclic voltammetry and chronoamperommetry. Osmium redox complexes were immobilized on the screen printed carbon electrode(SPE) with deposited gold nanoparticles. The electrical signal converts the osmium redox films into an electrocatalyst for glucose oxidation. Each catalytic currents were related with the potentials of osmium complexes.

• Journal of Environmental Science International
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• v.13 no.5
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• pp.479-488
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• 2004

Five sediment cores from the tidal flat of artificial Lake Shihwa are analyzed in terms of sedimentology and geochemistry to evaluate the heavy metal contamination and redox condition of surficial sediment following the Shihwa seawall construction. The variability of concentrations of various elements depends on the depositional environment, and reflects the various redox conditions and sediment provenances. The amounts of Ti and Al and their ratio of Ti/ Al with respect to Li clearly indicate that there is an anthropogenic contribution to the surficial sediment. The high concentrations of heavy metals suggest an anthropogenic contribution at ST. 34 and ST. 22. Concentrations of most elements (Cr, Cu, Zn and Pb) are higher near the Shihwa-Banwol industrial complex than in the central part of Lake Shihwa. Concentrations of heavy metal in surficial sediment near the Shihwa-Banwol industrial complex are two to eight times higher than in the center of Lake Shihwa. Enrichment factors (EF), which are normalized by the unpolluted shale, suggests a significant metallic contamination near the Shihwa-Banwol industrial complex (SBIC). The redox condition is divided into two anoxic and mixed oxi $c_oxic zones based on the carbon:sulfur (C/S) ratios of organic matter and elemental relationships. Correlations among geochemical elements Mn, U and Mo are significantly different from site to site, and may therefore be an indicator of the spatial redox condition. Controlling factors for switching anoxic/oxic conditions are thought to be water depth and the differences in industrial effluent supply. The variations of the Cu/Mn ratio in the sediments confirms above mentioned spatial differences of a redox condition in part, and therefore shows a location-dependence redox condition in sediments at four other sites. The redox condition of the surficial sediment characteristics of the Shihwa Lake are controlled by its geographic location and water depth.th.

• Journal of the Korean Electrochemical Society
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• v.13 no.2
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• pp.123-127
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• 2010

An assembled-graphite/DSA(Dimensionally Stable Anode) was prepared using graphite powder to increase durability and energy efficiency of redox flow battery and investigated its electrochemical properties in vanadium-based electrolyte. The cyclic voltammetry (CV) was carried out in the voltage range of -0.7V and 1.6V vs. SCE at 5 mV/sec scan rate to analyze vanadium redox reaction. From the CV results, the assembled-graphite/DSA electrode showed a fast couple reaction and good reversibility in 2M $VOSO_4$ + 2.5 M $H_2SO_4$ electrolyte. Therefore, it has been expected that this electrode increases power density as well as energy density of redox flow battery.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.5
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• pp.721-727
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• 2011

All vanadium redox-flow battery (VRFB) has been studied actively as one of the most promising electrochemical energy storage systems for a wide rage of applications such as electric vehicles, photovoltaic arrays, and excess power generated by electric power plants at night time. In this study, carbon felt electrodes were treated by electrochemical oxidation with KOH, and the cyclic voltammetry were studied in order to investigate redox reactivity of vanadium ion species with carbon felt electrodes. Besides the effect of electrochemical oxidation on the surface chemistry of carbon felt electrodes were investigated using the X-ray photoelectron spectroscopy (XPS). After electrochemical oxidation, XPS analysis of PAN based GF20-3 carbon felt electrode revealed on increase in the overall surface oxygen content of the carbon felts after electrochemical oxidation. Redox reaction characteristics using cyclic voltammetry (CV) were ascertained that the electrochemical treated electrode were more reversible than the untreated electrode.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.1
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• pp.21-30
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• 2006

[ $M/Fe_2O_3$ ] (M=Rh, Ce and Zr) mixed oxides were prepared using urea method to develop a medium for chemical hydrogen storage by their redox cycles. And their redox behaviors by repeated cycles were studied using temperature programmed reaction(TPR) technique. Additives such as Rh, Ce and Zr were added to iron oxides in order to lower the reaction temperature for reduction by hydrogen and re-oxidation by water-splitting. From the results, concentration of urea used as a precipitant had little effect on particle size and reduction property of iron oxide. TPR patterns of iron oxide consisted of two reduction peaks due to the course of $Fe_2O_3\;{\rightarrow}\;Fe_3O_4\;{\rightarrow}\;Fe$. The results of repeated redox tests showed that Rh added to iron oxide have an effect on lowering the re-oxidation temperature by water-splitting. Meanwhile, Ce and Zr additives played an important role in prevention of deactivation by repeated cycles. Finally, Fe-oxide(Rh, Ce, Zr) sample added with Rh, Ce and Zr showed the lowest re-oxidation temperature by water-splitting and maintained high $H_2$ recovery in spite of the repeated redox cycles. Consequently, it is expected that Fe-oxide(Rh, Ce, Zr) sample can be a feasible medium for chemical hydrogen storage using redox cycle of iron oxide.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.671-676
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• 2013

Recently, there are many efforts focused on development of Redox Flow Battery (RFB) for large energy storage system. Economical hydrocarbon membranes alternative to fluorinated membranes for RFB membrane are receiving attention. In this study, characteristics of poly(arylene ether sulfone) (PAES) were compared with expensive fluorinated membrane at VRB (Vanadium Redox Flow Battery) operation condition. Permeability of vanadium ion through membrane, ion exchange capacity (IEC), change of OCV, swelling, charge-discharge curves and energy efficiency were measured. PAES membrane showed lower permeability of vanadium ion, higher IEC and then higher energy efficiency compared with Nafion 117 membranes.

• Journal of the Korean Electrochemical Society
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• v.10 no.2
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• pp.150-154
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• 2007

Redox complexes to transport electrodes from biomaterial to electrodes are very important part in commercial biosensor industry. A novel osmium redox complex was synthesized by the coordinating pyridine group with osmium metal. A novel osmium complex is described as $[Os(dme-bpy)_2(ap-im)Cl]^{+/2+}$. We have been studied the electrochemical characteristics of this osmium complex with electrochemical techniques such as cyclic voltammetry and chronoamperommetry. In order to immobilize osmium redox complexes on the electrode, we deposited gold nano-particles on screen printed carbon electrode(SPE). The electrical signal converts the osmium redox films into an electrocatalyst for glucose oxidation. The catalytic currents were monitored that the catalytic currents were linearly increased from 1 mM to 5 mM concentrations of glucose.