• 대한화학회지
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• 제60권5호
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• pp.310-316
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• 2016

Oxidation-reduction cycling (ORC) procedures are widely used for cleaning nanoparticle surfaces when investigating their electrocatalytic activities. In this work, the effect of ORC on the surface structures and electrocatalytic oxygen reduction activity of Au electrodes is analyzed. Different structural changes and variations in electrocatalysis are observed depending on the initial structure of the Au electrodes, such as flat bulk, nanoporous, nanoplate, or dendritic Au. In particular, dendritic Au structures lost their sharp-edge morphology during the ORC process, resulting in a significant decrease in its electrocatalytic oxygen reduction activity. The results shown in this paper provide an insight into the pretreatment of nanoparticle-based electrodes during investigation of their electrocatalytic activities.

• 대한화학회지
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• 제29권2호
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• pp.172-177
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• 1985

안티몬이 첨가된 산화주석 얇은막 전극의 반도체적 성질을 조사하고 이산화황의 산화반응에 대한 이 전극의 전기화학적 촉매작용을 여러가지 조건하에서 조사하였다. $SO_2$(또는 아황산염)를 포함하는 전해질 용액의 pH가 증가함에 따라 점차로 낮은 전위에서 산화가 일어났으며 이 전극은 염기성 용액에서 $SO_3^=$의 산화에 대하여 뚜렷한 전기촉매 작용을 나타내었으며 이 전기촉매 작용은 백금이나 팔라듐 전극의 촉매작용과는 다른 특성을 보여주었다. 백금이나 팔라듐이 이 전극에 첨가된 경우에는 이들 금속이 전극표면에 노출된 양에 비례하는 효과만이 나타났다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.369-372
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• 2009

In the present study, the effect of chemical treatment on graphite nanofibers (GNFs) supports with various concentrated nitric acids was investigated for methanol oxidation. To optimize the electrocatalytic activity, PtRu catalysts were deposited on GNF supports by impregnation method. The surface and structural properties of the GNF supports were characterized by X-ray photoelectron spectroscopy (XPS), element analyzer (EA), and X-ray diffraction (XRD). The morphology of the catalysts was observed by means of transmission electron microscopy (TEM). The electrocatalytic activity of PtRu/GNF catalysts was investigated by cyclic voltammetry measurement. As a result, the oxygen functional groups were introduced on the GNF supports and were gradually increased with increasing of concentrated nitric acid, causing the smaller particle size and higher loading level. And the electrocatalytic activity of the catalysts for methanol oxidation was gradually improved. Consequently, it was found that chemical treatments could influence on surface properties of the carbon supports, resulting in enhancing the electrocatalytic activity of the catalysts for DMFCs.

• Journal of Electrochemical Science and Technology
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• 제3권1호
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• pp.24-28
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• 2012

The electrocatalytic activities and surface roughness of indium-tin-oxide (ITO) electrodes have been investigated after thermal treatment at 100, 150, or $200^{\circ}C$ for 30 min, 2 h, or 8 h. To check electrocatalytic activities, the electrochemical behavior of four electroactive species (p-hydroquinone, $Ru(NH_3){_6}^{3+}$, ferrocenemethanol, and $Fe(CN){_6}^{4-}$) has been measured. The electron transfer rate for p-hydroquinone oxidation and ferrocenemethanol oxidation increases with increasing the incubation temperature and the incubation period of time, but the rate for $Ru(NH_3){_6}^{3+}$ is similar irrespective of the incubation temperature and period because $Ru(NH_3){_6}^{3+}$ undergoes a fast outer-sphere reaction. Overall, the electrocatalytic activities of ITO electrodes increase with increasing the incubation temperature and period. The surface roughness of ITO electrodes increases with increasing the incubation temperature, and the thermal treatment generates many towering pillars as high as several tens of nanometer.

• 분석과학
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• 제8권4호
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• pp.617-622
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• 1995

Electrocatalytic reduction of dioxygen has been investigated by cyclic voltammetry at glassy carbon electrode modified with new Co(II)-Schiff base complexes in aqueous solutions of various pH. The reduction potentials of dioxygen at chemically adsorbed electrodes show the dependence of pH between pH 4 and 14. The catalytic effect is large and the reaction occurs via two or four electron transfer in various pH solution.

• 전기화학회지
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• 제16권2호
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• pp.70-73
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• 2013

산화 이리듐은 물의 산화반응에 대해 좋은 전기촉매 물질로서 많은 연구가 이루어 지고 있다. 최근 전기화학적 증폭방법을 이용하여 산화 이리듐 나노입자의 개별적인 촉매특성을 연구한 결과를 보면 촉매반응에 의한 전류가 지속적으로 유지되지 않고 시간에 따라 감소하는 결과가 얻어 졌다. 이러한 촉매특성의 사라짐에 대한 원인을 규명하고자 사이즈가 큰 이리듐전극을 산화시킨 산화이리듐 전극에서 물의 산화반응을 진행시켰다. 그 결과 나노입자에서와 유사하게 전류가 감소하는 현상이 관찰되었다. 큰 전극에서의 실험에서는 발생하는 산소방울을 관찰 할 수 있었는데 산소방울의 발생 주기가 전류의 증감주기와 일치하는 것으로 보아 전류의 감소는 산소방울에 의한 버블 과전압 때문으로 생각된다.

• Bulletin of the Korean Chemical Society
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• 제19권4호
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• pp.417-422
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• 1998

The electrocatalytic reduction of molecular oxygen was investigated with a Co(II)-glyoxal bis(2-hydroxyanil) complex coated-glassy carbon (GC) electrode in aqueous media. The reduction of $O_2$ at the modified electrode was an irreversible and diffusion-controlled reaction. The complex coated-GC electrode demonstrated an excellent electrocatalytic effect for $O_2$ reduction in an acetate buffer solution of pH 3.2. The coated electrode made the $O_2$ reduction potential shift of 60-510 mV in a positive direction compared to the bare GC electrode depending on pH. The Co(II)-glyoxal bis(2-hydroxyanil) coated electrode converted about 51% of the $O_2$ to $H_2O_2$ via a two-electron reduction pathway, with the balance converted to H_2O$.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.331-334
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• 2010

In the present study, carbon supports mixed with purified multi-walled carbon nanotubes (MWNTs) and carbon blacks (CBs) were used to improve the cell performance of direct methanol fuel cells (DMFCs). Additionally, the effect of $O_2$ plasma treatment on CBs/MWNTs supports was investigated for different plasma RF powers of 100, 200, and 300 W. The surface and structural properties of the CBs/MWNTs supports were characterized by FT-IR, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and inductive coupled plasma-mass spectrometer (ICP-MS). The electrocatalytic activity of PtRu/CBs/MWNTs catalysts was investigated by cyclic voltammetry measurement. In the experimental results, the oxygen functional groups of the supports were increased with increasing plasma RF power, while the average Pt particle size was decreased owing to the improvement of dispersibility of the catalysts. The electrochemical activity of the catalysts for methanol oxidation was gradually improved by the larger available active surface area, itself due to the introduction of oxygen functional groups. Consequently, it was found that $O_2$ plasma treatments could influence the surface properties of the carbon supports, resulting in enhanced electrocatalytic activity of the catalysts for DMFCs.

• Bulletin of the Korean Chemical Society
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• 제33권6호
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• pp.1829-1833
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• 2012

Titania spheres were synthesized using binary ionic liquids to examine the electrocatalytic activity in acid solution. The morphology of $TiO_2$ particles was significantly different with the composition of ionic liquids. Among the binary ionic liquids, four set of mixtures led to the formation of $TiO_2$ sphere with various sizes. The morphology and structure of $TiO_2$ particles were characterized by XRD, $N_2$ physisoption and SEM analysis. All samples possessed an anatase phase after calcinations at $500^{\circ}C$. The structural properties of the samples were varied significantly with the morphology. In cyclic voltammograms, the morphology of $TiO_2$ spheres affected the electrocatalytic activity in water electrolysis. Among the samples, [Omim][$BF_4$]+[Hmim][$BF_4$] was the most effective ionic liquid to synthesize $TiO_2$ sphere with optimum morphology showing the highest electocatalytic performance.

• 한국수소및신에너지학회논문집
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• 제20권2호
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• pp.95-103
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• 2009

In order to improve the electrochemical, mechanical and electrocatalytic characteristics, engineering plastic of polyether ether ketone (PEEK) as polymer matrix was sulfonated (SPEEK) and the organic-inorganic blend composite membranes has been prepared by loading heteropoly acids (HPAs), including tungstophosphoric acid (TPA), molybdophosphoric acid (MoPA), and tungstosilicic acid (TSiA). And then these were covalently cross-linked (CL-SPEEK/HPA) as the electrolyte and MEA of polymer electrolyte membrane electrolysis (PEME). As a result, the optimum reaction conditions of CL-SPEEK/HPA was established and the electrochemical characteristics such as ion conductivity ($\sigma$) were in the order of magnitude: CL-SPEEK /TPA30 (${\sigma}=0.128\;S/cm^{-1}$) < /MoPA40 (${\sigma}=0.14\;S/cm^{-1})$ < /TSiA30 (${\sigma}=0.22\;S/cm^{-1}$) at $80^{\circ}C$, and mechanical characteristics such as tensile strength: CL-SPEEK /TSiA30 $\fallingdotseq$ /MoPA40 < /TPA30. Consequently, in regards of above characterisitics and oxidation durability, the CL-SPEEK/TPA30 exhibited a better performance in PEME than the others, but CL-SPEEK/MoPA40 showed the best electrocatalytic activity of cell voltage 1.71 V among the composite membranes. The dual effect of higher proton conductivity and electrocatalytic activity with the addition of HPAs, causes a synergy effect.