scholarly journals Effect of glassy carbon properties on the electrochemical deposition of platinum nano-catalyst and its activity for methanol oxidation

2007 ◽  
Vol 72 (2) ◽  
pp. 165-181 ◽  
Author(s):  
Sanja Terzic ◽  
Dusan Tripkovic ◽  
Vladislava Jovanovic ◽  
Amalija Tripkovic ◽  
Andrzej Kowal
Keyword(s):  
Methanol Oxidation ◽  
Glassy Carbon ◽  
Specific Activity ◽  
Carbon Support ◽  
Pt Electrode ◽  
Nano Catalyst ◽  
Platinum Particles ◽  
Different Temperatures ◽  
Order Of Magnitude ◽  
Anodic Polarisation

The effects of the properties of glassy carbon on the deposition of platinum particles and the electrocatalytic activity of platinum supported on glassy carbon (GC/Pt) for methanol oxidation in alkaline and acidic solutions were studied. Platinum was potentiostatically deposited on two glassy carbon samples, thermally treated at different temperatures, which were either polished or anodicaly polarised in acid (GCOX-AC/Pt) and in alkali (GCOX-AL/Pt). Anodic polarisation of glassy carbon, either in alkaline or acidic solution, enhances the activity of both types of GC/Pt electrodes for methanol oxidation. The activity of the catalysts follows the change in the properties of the glassy carbon support upon anodic treatment. The specific activity of the GCOX-AL/Pt electrode for this reaction in alkali is increased only a few times in comparison with the activity of the GC/Pt one. On the other hand, the specific activity of the GCOX-AC/Pt electrode for methanol oxidation in acid is about one order of magnitude higher than that of the GC/Pt electrode. The role of the substrate on the properties of catalyst is discussed in detail. .

scholarly journals Electrochemical and microstructural characterization of platinum supported on glassy carbon

2007 ◽  
Vol 61 (3) ◽  
pp. 135-141
Author(s):  
Sanja Terzic ◽  
Vladislava Jovanovic ◽  
Dusan Tripkovic ◽  
Andrzej Kowal ◽  
Jerzy Stoch
Keyword(s):  
Methanol Oxidation ◽  
Glassy Carbon ◽  
Microstructural Characterization ◽  
Electrochemical Treatment ◽  
Organic Residues ◽  
Remarkable Effect ◽  
Platinum Particles ◽  
Order Of Magnitude

The effect of the electrochemical oxidation of glassy carbon on the deposition of platinum particles and the electrocatalytic activity of platinum supported on oxidized glassy carbon were studied for methanol oxidation in H2SO4 solution. Platinum was potentiostatically deposited from H2SO4 + 6mM H2PtCl6 solution. Glassy carbon was anodically polarized in 1 M NaOH at 1.41 V (SCE) for 35 and 95 s and in 0.5 M H2SO4 at 2V (SCE) for 35; 95 s and 2.25 V for 35 and 95 s. Electrochemical treatment of the GC support leads to a better distribution of platinum on the substrate and has remarkable effect on the activity. The activity of the Pt/GCox electrode for methanol oxidation is larger than that of polycrystalline Pt and by more than one order of magnitude larger than that of a Pt/GC electrode. This increase in activity indicates the pronounced role of the organic residues of the GC support on the properties of Pt particles deposited on glassy carbon.

Coadsorption of bulky ions by surfactants. Monomolecular layers of tris(2,2'-bipyridyl)ruthenium(II) complex with sodium lauryl sulphate on glassy carbon, platinium, n-SnO2, and n-Si electrodes

1984 ◽  
Vol 49 (10) ◽  
pp. 2187-2196 ◽  
Author(s):  
Jan Lasovský ◽  
František Grambal ◽  
Miroslav Rypka
Keyword(s):  
Glassy Carbon ◽  
Complex Cation ◽  
Radiant Energy ◽  
Electric Energy ◽  
Sodium Lauryl Sulphate ◽  
Surface Films ◽  
Order Of Magnitude ◽  
Monomolecular Layers ◽  
Self Association ◽  
Semiconductor Electrodes

The electrochemical and photochemical behaviour of tris(2,2'-bipyridyl)ruthenium(II) complex (I) on glassy carbon, platinium, n-SnO2, and n-Si electrodes in the presence of sodium lauryl sulphate (II) was investigated. The surfactant in low concentrations induces self-association of the complex cation and its accumulation in the electrode-solution interface. At the optimum concentrations of sodium lauryl sulphate (cII ~0.6 mmol l-1) and of the complex (cI < 0.1 mmol l-1), monomolecular layers composed of I, II counterions are formed on the electrodes. The formation of the surface films does not depend on the kind of the electrode and improves the sensitivity of the voltammetric determination of I by as much as an order of magnitude. For the semiconductor electrodes, the surface films enhance the efficiency of conversion of radiant energy into electric energy. The effect under study may participate in the photosynthesis of green plants.

Kinetic and Thermodynamic Characterization of Lignin Peroxidase Isolated from Agaricus bitorqus A66

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Ismat Bibi ◽  
Haq Nawaz Bhatti
Keyword(s):  
Lignin Peroxidase ◽  
Thermal Inactivation ◽  
Specific Activity ◽  
Gel Filtration ◽  
Veratryl Alcohol ◽  
Exchange Chromatography ◽  
Different Temperatures ◽  
Scale Experiment ◽  
Menten Kinetic

This study deals with purification and characterization of lignin peroxidase (LiP) isolated from Agaricus bitorqus A66 during decolorization of NOVASOL Direct Black dye. A laboratory scale experiment was conducted for maximum LiP production under optimal conditions. Purification & fractionation of LiP was performed on DEAE-Sepharose ion exchange chromatography followed by Sephadex G-50 gel filtration. The purified LiP has a specific activity of 519 U/mg with 6.73% activity recover. The optimum pH and temperature of purified LiP for the oxidation of veratryl alcohol were 6.8 and 45 °C, respectively. Michaelis-Menten kinetic constants (Vmax and Km) were determined using different concentrations of veratryl alcohol (1-35 mM). The Km and Vmax were 16.67 mM and 179.2 U/mL respectively, for veratryl alcohol oxidation as determined from the Lineweaver-Burk plot. Thermal inactivation studies were carried out at different temperatures to check the thermal stability of the enzyme. Enthalpy of activation decreased where Free energy of activation for thermal denaturation increased at higher temperatures. A possible explanation for the thermal inactivation of LiP at higher temperatures is also discussed.

scholarly journals Re-evaluation of the interaction of malonyl-CoA with the rat liver mitochondrial carnitine palmitoyltransferase system by using purified outer membranes

1990 ◽  
Vol 267 (1) ◽  
pp. 85-90 ◽  
Author(s):  
M P Kolodziej ◽  
V A Zammit
Keyword(s):  
Rat Liver ◽  
Specific Activity ◽  
Liver Mitochondria ◽  
Subsequent Treatment ◽  
Carnitine Palmitoyltransferase ◽  
Rat Liver Mitochondria ◽  
Outer Membranes ◽  
High Affinity ◽  
Malonyl Coa ◽  
Order Of Magnitude

1. The interaction of malonyl-CoA with the outer carnitine palmitoyltransferase (CPT) system of rat liver mitochondria was re-evaluated by using preparations of highly purified outer membranes, in the light of observations that other subcellular structures that normally contaminate crude mitochondrial preparations also contain malonyl-CoA-sensitive CPT activity. 2. In outer-membrane preparations, which were purified about 200-fold with respect to the inner-membrane-matrix fraction, malonyl-CoA binding was largely accounted for by a single high-affinity component (KD = 0.03 microM), in contrast with the dual site (low- and high-affinity) previously found with intact mitochondria. 3. There was no evidence that the decreased sensitivity of CPT to malonyl-CoA inhibition observed in outer membranes obtained from 48 h-starved rats (compared with those from fed animals) was due to a decreased ratio of malonyl-CoA binding to CPT catalytic moieties. Thus CPT specific activity and maximal high-affinity [14C]malonyl-CoA binding (expressed per mg of protein) were increased 2.2- and 2.0-fold respectively in outer membranes from 48 h-starved rats. 4. Palmitoyl-CoA at a concentration that was saturating for CPT activity (5 microM) decreased the affinity of malonyl-CoA binding by an order of magnitude, but did not alter the maximal binding of [14C]malonyl-CoA. 5. Preincubation of membranes with either tetradecylglycidyl-CoA or 2-bromopalmitoyl-CoA plus carnitine resulted in marked (greater than 80%) inhibition of high-affinity binding, concurrently with greater than 95% inhibition of CPT activity. These treatments also unmasked an effect of subsequent treatment with palmitoyl-CoA to increase low-affinity [14C]malonyl-CoA binding. 6. These data are discussed in relation to the possible mechanism of interaction between the malonyl-CoA-binding site and the active site of the enzyme.

Carbon Supported Pt+Os Catalysts for Methanol Oxidation

2002 ◽  
Vol 57 (2) ◽  
pp. 193-201 ◽  
Author(s):  
Gülsün Gökağaç ◽  
Brendan J. Kennedy
Keyword(s):  
Methanol Oxidation ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
Carbon Support ◽  
Methanol Oxidation Reaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Metal Metal ◽  
Metal Support

11% Pt/C, 10% Pt + 1%Os/C, 9% Pt + 2%Os/C, 8% Pt + 3%Os/C, 7% Pt + 4%Os/C, 6% Pt + 5%Os/C and 5%Pt + 6% Os/C catalysts have been prepared for methanol oxidation reaction. Transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and cyclic voltammetry have been used to understand the nature of the species present in these catalysts. 7% Pt + 4% Os/C was the most active catalyst, while 8% Pt + 3% Os/C was the least active one. It is found that the metal particle size and distribution on the carbon support, the surface composition and the oxidation states of the metal particles, the metal-metal and metal support interactions are important parameters to define the activity of the catalyst.

Lipolytic activity of ricin from Ricinus sanguineus and Ricinus communis on neutral lipids

2001 ◽  
Vol 358 (3) ◽  
pp. 773-781 ◽  
Author(s):  
Sophie LOMBARD ◽  
Mohamed E. HELMY ◽  
Gérard PIÉRONI
Keyword(s):  
Surface Pressure ◽  
Specific Activity ◽  
Neutral Lipids ◽  
Ricinus Communis ◽  
Lipolytic Activity ◽  
Fatty Acid Esters ◽  
Lipid Monolayer ◽  
Serine Esterase ◽  
Order Of Magnitude ◽  
Esterase Inhibitor

The present study was carried out with a view of determining ricin lipolytic activity on neutral lipids in emulsion and in a membrane-like model. Using 2,3-dimercapto-1-propanol tributyrate (BAL-TC4) as substrate, the lipolytic activity of ricin was found to be proportional to ricin and substrate concentrations, with an apparent Km (Km,app) of 2.4mM, a kcat of 200min−1 and a specific activity of 1.0unit/mg of protein. This work was extended to p-nitrophenyl (pNP) fatty acid esters containing two to twelve carbon atoms. Maximum lipolytic activity was registered on pNP decanoate (pNPC10), with a Km,app of 3.5mM, a kcat of 173min−1 and a specific activity of 3.5units/mg of protein. Ricin lipolytic activity is pH and galactose dependent, with a maximum at pH7.0 in the presence of 0.2M galactose. Using the monolayer technique with dicaprin as substrate, ricin showed a lipolytic activity proportional to the ricin concentration at 20mN/m, which is dependent on the surface pressure of the lipid monolayer and is detectable up to 30mN/m, a surface pressure that is of the same order of magnitude as that of natural cell membranes. The methods based on pNPC10 and BAL-TC4 hydrolysis are simple and reproducible; thus they can be used for routine studies of ricin lipolytic activity. Ricin from Ricinus communis and R. sanguineus were treated with diethyl p-nitrophenylphosphate, an irreversible serine esterase inhibitor, and their lipolytic activities on BAL-TC4 and pNPC10, and cytotoxic activity, were concurrently recorded. A reduction in lipolytic activity was accompanied by a decrease in cytotoxicity on Caco2 cells. These data support the idea that the lipolytic activity associated with ricin is relevant to a lipase whose activity is pH and galactose dependent, sensitive to diethyl p-nitrophenylphosphate, and that a lipolytic step may be involved in the process of cell poisoning by ricin. Both colorimetric tests used in this study are sensitive enough to be helpful in the detection of possible lipolytic activities associated with other cytotoxins or lectins.

scholarly journals A high-performance oxygen evolution catalyst in neutral-pH for sunlight-driven CO2 reduction

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Li Qin Zhou ◽  
Chen Ling ◽  
Hui Zhou ◽  
Xiang Wang ◽  
Joseph Liao ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
High Performance ◽  
Specific Activity ◽  
Co2 Reduction ◽  
Poor Performance ◽  
Electrolysis Cell ◽  
Neutral Ph ◽  
Highly Active ◽  
Order Of Magnitude ◽  
Neutral Conditions

Abstract The efficiency of sunlight-driven reduction of carbon dioxide (CO2), a process mimicking the photosynthesis in nature that integrates the light harvester and electrolysis cell to convert CO2 into valuable chemicals, is greatly limited by the sluggish kinetics of oxygen evolution in pH-neutral conditions. Current non-noble metal oxide catalysts developed to drive oxygen evolution in alkaline solution have poor performance in neutral solutions. Here we report a highly active and stable oxygen evolution catalyst in neutral pH, Brownmillerite Sr2GaCoO5, with the specific activity about one order of magnitude higher than that of widely used iridium oxide catalyst. Using Sr2GaCoO5 to catalyze oxygen evolution, the integrated CO2 reduction achieves the average solar-to-CO efficiency of 13.9% with no appreciable performance degradation in 19 h of operation. Our results not only set a record for the efficiency in sunlight-driven CO2 reduction, but open new opportunities towards the realization of practical CO2 reduction systems.

High Efficiency Photoelectrocatalytic Methanol Oxidation on CdS Quantum Dots Sensitized Pt Electrode

2016 ◽  
Vol 8 (9) ◽  
pp. 5972-5980 ◽  
Author(s):  
Chunyang Zhai ◽  
Mingshan Zhu ◽  
Fenzhi Pang ◽  
Duan Bin ◽  
Cheng Lu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Methanol Oxidation ◽  
High Efficiency ◽  
Cds Quantum Dots ◽  
Pt Electrode
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