• Journal of the Korean Chemical Society
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• v.37 no.4
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• pp.462-469
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• 1993

The electrocatalytic reduction of dioxygen is investigated by cyclic voltammetry and chronoamperometry at glassy carbon electrode and carbon microelectrode coated with a variety of cobalt phenylporphyrins. The n value obtained at carbon microelectrode is slightly different from that determined at glassy carbon electrode. Dioxygen reduction catalyzed by the monormeric porphyrin Co(II)-TPP mainly occurs through the $2e^-$ reduction pathway resulting in the formation of hydrogen peroxide, electrocatalytic process carries out $4e^-$ reduction pathway of dioxygen to $H_2O$ at the electrodes coated with bis-cobalt phenylporphyrins. The electrocatalytic reduction of dioxygen is irreversible and diffusion controlled.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3668-3674
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• 2010

Mesoporous SBA-15 was synthesized using tetraethylorthosilicate (TEOS) as the silica source and Pluronic (P123) as the structure-directing agent. The defective Si-OH groups present in SBA-15 were successively grafted with 3-chloropropyltrimethoxysilane (CPTMS) followed by tris-(2-aminoethyl) amine (TAEA) and/or tetraethylenepentamine (TEPA) for effective immobilization of silver nanoparticles. Grafting of TAEA and/or TEPA amine and immobilization of silver nanoparticles inside the channels of SBA-15 was verified by XRD, TEM, IR and BET techniques. The silver nanoparticles immobilized on TAEA and /or TEPA grafted SBA-15 was subjected for electrocatalytic reduction of hydrogen peroxide ($H_2O_2$). The TEPA stabilized silver nanoparticles show higher efficiency for reduction of $H_2O_2$ than that of TAEA, due to higher number of secondary amine groups present in TEPA. The amperometric analysis indicated that both the Ag/SBA-15/TAEA and Ag/SBA-15/TEPA modified electrodes required lower over-potential and hence possess high sensitivity towards the detection of $H_2O_2$. The reduction peak currents were linearly related to hydrogen peroxide concentration in the range between $3{\times}10^{-4}\;M$ and $2.5{\times}10^{-3}\;M$ with correlation coefficient of 0.997 and detection limit was $3{\times}10^{-4}\;M$.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.133-133
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• 2013

For both oxygen reduction (ORR) and hydrogen oxidation reactions (HOR) of proton electrolyte membrane fuel cells (PEMFCs), alloying Pt with another transition metal usually results in a higher activity relative to pure Pt, mainly due to electronic modification of Pt and bifunctional behaviour of alloy surface for ORR and HOR, respectively. However, activity and stability are closely related to the preparation of alloy nanoparticles. Preparation conditions of alloy nanoparticles have strong influence on surface composition, oxidation state, nanoparticle size, shape, and contamination, which result from a large difference in redox priority of metal precursors, intrinsic properties of metals, increasedreactivity of nanocrystallites, and interactions with constituents for the synthesis such as solvent, stabilizer, and reducing agent, etc. Carbon-supported Pt-Ni alloy nanoparticles were prepared by the borohydride reduction method in anhydrous solvent. Pt-Ru alloy nanoparticles supported on carbon black were also prepared by the similar synthetic method to that of Pt-Ni. Since electrocatalytic reactions are strongly dependent on the surface structure of metal catalysts, the atom-leveled design of the surface structure plays a significant role in a high catalytic activity and the utilization of electrocatalysts. Therefore, surface-modified electrocatalysts have attracted much attention due to their unique structure and new electronic and electrocatalytic properties. The carbon-supported Au and Pd nanoparticles were adapted as the substrate and the successive reduction process was used for depositing Pt and PtM (M=Ru, Pd, and Rh) bimetallic elements on the surface of Au and Pd nanoparticles. Distinct features of the overlayers for electrocatalytic activities including methanol oxidation, formic acid oxidation, and oxygen reduction were investigated.

• Journal of the Mineralogical Society of Korea
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• v.18 no.1
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• pp.1-9
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• 2005

The electrocatalytic reduction of O₂ was investigated with methyl viologen and methylene blue incorporated clay-modified electrodes. Clay suspensions were prepared with Na-montmorillonite, Ca-montmorillonite, and kaolinite. The methyl viologen-clay modified electrodes were made by coating clay suspensions adsorbing methyl viologen on a glassy carbon electrode. Cyclic voltammetry were performed in aqueous media to investigate the electrocatalytic property of the modified electrode in reducing O₂. A Na-montmorillonite modified electrode showed the greatest adsorption capacity for methyl viologen. The modified electrode made of Na-montmorillonite suspension of 0.87 g/10 mL and a 2.5 mM of methyl viologen solution showed the most effective electrocatalytic property, where the catalytic reduction potential was shifted by 242.6 mV toward the positive potential. The electrocatalytic ability was more significant in acidic (pH=3.7) and alkaline (pH=12.7) media than the neutral pH range (6.3∼8.3). The methyl viologen-Na-montmorillonite modified electrode had the good reproducibility and maintain the electrocatalytic property over 20 times reuse.

• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.251-255
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• 2010

We report on the electrocatalytic reduction of hydrogen peroxide at nanoporous gold (NPG) surfaces. Various NPG surfaces with different surface structure were prepared by changing the conditions of electrodeposition for Ag-Au layers such as the concentration ratios of $KAu(CN)_2$ over $KAg(CN)_2$ and deposition charges. The effects of different electrochemical conditions on the electrocatalysis of $H_2O_2$ reduction were investigated. The NPG surfaces exhibited sensitive amperometric responses for $H_2O_2$ reduction, from which calibration plots with higher sensitivity than a bare Au surface were obtained.

• 한국전기화학회:학술대회논문집
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• 2004.04a
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• pp.26-26
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• 2004

• Bulletin of the Korean Chemical Society
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• v.19 no.7
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• pp.795-797
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• 1998

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.316-319
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• 2006

There is a worldwide interest in the development and commercialization of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) for vehicular and stationary applications. One of the major objectives is the reduction of loaded electrode materials, which is comprise of the Pt-based noble metals. In this paper, a novel chemical strategy is described for the preparation and characterization of carbon-supported and surface-alloys, which were prepared by using a successive reduction process. After preparing Au colloid nanoparticles, the deposition of Au colloid nanoparticles occurred spontaneously in the carbon black-dispersed aqueous solution. Then nano-scaled active materials were formed on the surface of carbon-supported Au nanoparticles. The structural and electrochemical analyses indicate that the active materials were deposited on the surface of Au nanoparticles selectively and that an at toying process occurred during the successive reducing process The carbon-supported & surface-alloys showed the higher electrocatalytic activity than those of the particle-alloys and commercial one (Johnson-Matthey) for the reaction of methanol and formic acid oxidation. The increased electrocatalytic activity might be attributed to the effective surface structure of surface-alloys, which have a high utilization of active materials for the surface reaction of electrode.

• New & Renewable Energy
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• v.2 no.4 s.8
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• pp.64-69
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• 2006

There is a worldwide interest in the development and commercialization of polymer electrolyte membrane fuel cells [PEMFCs] for vehicular and stationary applications. One of the major objectives is the reduction of loaded electrode materials, which is comprise of the Pt-based noble metals. In this paper, a novel chemical strategy is described for the preparation and characterization of carbon-supported and surface-alloys, which were prepared by using a successive reduction process. After preparing Au colloid nanoparticles, the supporting of Au colloid nanoparticles occurred spontaneously in the carbon black-dispersed aqueous solution. Then nano-scaled active materials were formed on the surface of carbon-supported Au nanoparticles. The structural and electrochemical analyses indicate that the active materials were deposited on the surface of Au nanoparticles selectively and that an alloying process occurred during the successive reducing process. The carbon-supported & surface-alloys showed the higher electrocatalytic activity than those of the particle-alloys and commercial one [Johnson-Matthey] for the reaction of methanol and formic acid oxidation. The increased electrocatalytic activity might be attributed to the effective surface structure of surface-alloys, which have a high utilization of active materials for the surface reaction of electrode.

• Journal of the Korean Electrochemical Society
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• v.15 no.2
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• pp.83-89
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• 2012

We investigate the electrocatalytic activities for oxygen reduction at nanoporous gold (NPG) surfaces fabricated by selective dissolution of Ag from electrodeposited Ag-Au layers on electrode surfaces. The structure of NPG was controlled by changing the concentration ratios of precursor metal complexes during the electrodeposition of Ag-Au layers and the corresponding surface morphology and surface area was examined. NPG structures with Ag/Au ratio of 2.0 exhibited the highest electrocatalytic activity for oxygen reduction, where the nanoporous structure plays a key role, but the surface area does not affect on the electrocatalytic activity. The mechanism of electroreduction of oxygen was investigated by rotating disk electrode techniques. In acidic media, oxygen was first reduced to hydrogen peroxide followed by further reduction to water through 2-step 4-electron mechanism, whereas the oxygen was reduced directly to water by 4-electron mechanism in basic media.