scholarly journals The kinetics and mechanism of methanol oxidation on Pt and PtRu catalysts in alkaline and acid media

2007 ◽  
Vol 72 (7) ◽  
pp. 709-712 ◽  
Author(s):  
Jelena Lovic
Keyword(s):  
Single Crystals ◽  
Methanol Oxidation ◽  
Ruthenium Catalysts ◽  
Alkaline Media ◽  
Pt Catalyst ◽  
Platinum Electrodes ◽  
Acid Media ◽  
Rate Determining Step ◽  
Langmuir Hinshelwood Mechanism ◽  
Ptru Catalysts

The kinetic of methanol electrochemical oxidation for a series of platinum and platinum-ruthenium catalysts was investigated. A correlation between the beginning of OHad adsorption and methanol oxidation was demonstrated on Pt single crystals and Pt nanocatalyst. The activity of the nano-structured Pt catalyst was compared with single crystal platinum electrodes assuming the Kinoshita model of nanoparticles. The ruthenium-containing catalysts shifted the onset of methanol oxidation to more negative potentials. The effect was more pronounced in acid than in alkaline media. Based on the established diagnostic criteria, the reaction between COad and OHad species according to the Langmuir-Hinshelwood mechanism was proposed as the rate determining step in alkaline and acid media on Pt and PtRu catalysts. .

scholarly journals Methanol oxidation at platinum electrodes in acid solution: Comparison between model and real catalysts

2006 ◽  
Vol 71 (12) ◽  
pp. 1333-1343 ◽  
Author(s):  
A.V. Tripkovic ◽  
S.LJ. Gojkovic ◽  
K.Dj. Popovic ◽  
J.D. Lovic
Keyword(s):  
Acid Solution ◽  
Methanol Oxidation ◽  
Specific Activity ◽  
High Surface ◽  
High Surface Area ◽  
Pt Catalyst ◽  
Platinum Electrodes ◽  
Hydroxyl Anion ◽  
Platinum Single Crystals ◽  
Supported Pt Catalyst

Methanol oxidation in acid solution was studied at platinum single crystals, Pt(hkl), as the model catalyst, and at nanostructural platinum supported on high surface area carbon, Pt/C, as the real catalyst. The linear extrapolation method was used to determine the beginning of hydroxyl anion adsorption. Structural sensitivity of the adsorption was proved and a correlation with the onset of the methanol oxidation current was established at all catalysts. Bisulfate and chloride anions were found to decrease the methanol oxidation rate, but probably did not influence the reaction parth. The specific activity for the reaction increased in the sequence Pt(110) <Pt/C < Pt(111), suggesting that the activity of the supported Pt catalyst can be correlated with the activities of the dominating crystal planes on its surface. .

Mn-Mo-O Catalysts for Methanol Oxidation. I. Preparation and Characterization of the Catalysts

1992 ◽  
Vol 57 (12) ◽  
pp. 2529-2538 ◽  
Author(s):  
Krasimir Ivanov ◽  
Penka Litcheva ◽  
Dimitar Klissurski
Keyword(s):  
Methanol Oxidation ◽  
Solution Concentration ◽  
Alkaline Media ◽  
Acidic Media ◽  
Chemical Methods ◽  
X Ray ◽  
Ph Values ◽  
Precipitate Composition

Mn-Mo-O catalysts with a different Mo/Mn ratio have been prepared by precipitation. The precipitate composition as a function of solution concentration and pH was studied by X-ray, IR, thermal and chemical methods. Formation of manganese molybdates with MnMoO4.1.5H2O, Mn3Mo3O12.2.5H2O, and Mn3Mo4O15.4H2O composition has been supposed. It is concluded that pure MnMoO4 may be obtained in both acid and alkaline media, the pH values depending on the concentration of the initial solutions. The maximum Mo/Mn ratio in the precipitates is 1.33. The formation of pure Mn3Mo4O15.4H2O is possible in weakly acidic media. This process is favoured by increasing the concentration of initial solutions.

PtRu Catalysts on Nitrogen-Doped Carbon Nanotubes with Conformal Hydrogenated TiO2 Shells for Methanol Oxidation

2022 ◽  
Author(s):  
Archana Sekar ◽  
Nathaniel Metzger ◽  
Sabari Rajendran ◽  
Ayyappan Elangovan ◽  
Yonghai Cao ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Methanol Oxidation ◽  
Nitrogen Doped ◽  
Ptru Catalysts ◽  
Nitrogen Doped Carbon

RHEOLOGICAL PROPERTIES OF HUMIC SUBSTANCES OF PEAT AND BROWN COAL

2021 ◽  
pp. 169-174
Author(s):  
Ivan I. Lishtvan ◽  
Vera N. Aleinikova
Keyword(s):  
Rheological Properties ◽  
Humic Substances ◽  
Structure Formation ◽  
Humic Substance ◽  
Brown Coal ◽  
Oil Wells ◽  
Alkaline Media ◽  
Rheological Parameters ◽  
Acid Media ◽  
Brown Coals

Knowledge about structure and rheological peculiarities of drilling solutions and reagents applied for the proceeding of oil wells has significant value for the forecasting of oil wells drilling. The research results of the structure of the humic substances of peat and brown coals precipitated in different pH ranges from the standpoint of their ability to structure formation on the base of the rheological curves obtaining of the flow of their dispersions and determining of their rheological parameters in terms of their application in drilling practice are given in the article. It is established that during transition from fraction, beset into alkaline media (12.0–8.5) to fraction beset into acid media (5.0–2.0) the decrease of the rheological indicators of caustobiolate humic substance is occurred. Rheological curves of the flow of the disperse of caustobiolate humic substances of the fraction 1 and 2 are characterized for strong fossil structures, disperses of humic substances of the fraction 3 is for less strong coagulation structures. Less structured are humic substances of brown coal so that their use is preferable for the regulation of the structure and rheological peculiarities of drilling solutions.

Na+/NH4+, Na+/H+ Exchanges and NH3 Movement Across the Gill of Carassius Auratus

1973 ◽  
Vol 58 (1) ◽  
pp. 255-275 ◽  
Author(s):  
J. MAETZ
Keyword(s):  
Carassius Auratus ◽  
External Medium ◽  
Ammonia Excretion ◽  
Alkaline Media ◽  
Ionic Balance ◽  
Free Base ◽  
Acid Media ◽  
Base Form ◽  
Monovalent Ions ◽  
The Law

1. Sodium exchange, ammonia excretion and H+ ion movement across the gill were measured in sodium-depleted Carassius auratus. Sodium uptake and ammonia excretion are considerably enhanced by sodium depletion. In this respect sodium-depleted fish behave as ammonia-loaded fish. 2. A decrease of the external pH by one unit results in a 50-60% decrease in both influx and efflux of sodium. A transient augmentation of the rate of ammonia excretion is observed upon acidification, suggesting an increased permeability of the gill to the free-base form of ammonia. 3. The ionic balance sheet of the movements of the monovalent ions across the gill was drawn up when a permeant co-ion for sodium was absent from the external medium. In both acid and alkaline media the ionic balance was achieved in accordance with the law of electroneutrality of external and internal solutions. 4. Net Na+ uptake was only found to be correlated to NH4+ excretion if H+ ion movements across the gill were taken into account. 5. Ammonia-gradient experiments were performed to test the ability of the gill to excrete ammonia against a gradient of ammonia partial pressure. Ammonia excretion is independent of this gradient in alkaline media when sodium ions are present. In these conditions ammonia moves in the ionic form. In acid media, with Na present in the external medium, ammonia movement is correlated with the pNH3 gradient but uphill movement still occurs. Ammonia moves in both the free-base and the ionized forms. In the absence of external sodium, movements of ammonia obey the law for passive transfer and ammonia moves exclusively in the free-base form, even though the external medium is alkaline.

Simple synthesis of Pt-Ag/SnO2-C for use as a catalyst of methanol oxidation in alkaline media

2017 ◽  
Vol 21 (8) ◽  
pp. 2449-2456 ◽  
Author(s):  
B. Ruiz-Camacho ◽  
A. Medina-Ramírez ◽  
R. Fuentes-Ramírez ◽  
Claudia M. Gómez
Keyword(s):  
Methanol Oxidation ◽  
Simple Synthesis ◽  
Alkaline Media
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