scholarly journals On the stability of platinum-composite electrocatalysts prepared with different substrate materials

2016 ◽  
Vol 6 (1) ◽  
pp. 29
Author(s):  
Milica G. Košević ◽  
Gavrilo M. Šekularac ◽  
Vladimir V. Panić
Keyword(s):  
Cyclic Voltammetry ◽  
Steady State ◽  
Sol Gel ◽  
Colloidal Dispersion ◽  
Sweep Rate ◽  
Initial Activity ◽  
Microwave Assisted ◽  
Commercial Carbon ◽  
The Stability ◽  
Cv Measurements

<p><span lang="EN-US">Cyclic voltammetry (CV) measurements were conducted and analyzed for a preliminary estimation of the stability of composite electrocatalysts based on Pt. The changes in CV currents of platinum nanoparticles supported on TiO<sub>2</sub> were compared to the changes of those supported on commercial carbon. TiO<sub>2</sub> was synthesized by sol-gel method and Pt was deposited from Pt colloidal dispersion synthesized by microwave-assisted polyol process. It was found that Pt component in both Pt/TiO<sub>2</sub> and Pt/C behaves similarly with respect to stability and activity during the cycling. The loss in activity with cycling was linear and strongly depended on sweep rate, i.e., the relative loss is higher at lower sweep rates. The steady state activities for both electrocatalysts were reached at the level of 65 % of initial activity and required more than 100 voltammetric cycles.</span></p>

Electrochromic and Electrochemical Properties of Nickel Oxide Thin Films Prepared by a Modified Sol-Gel Method

2008 ◽  
Vol 47-50 ◽  
pp. 625-629 ◽  
Author(s):  
X.H. Xia ◽  
J.P. Tu ◽  
J. Zhang ◽  
X.L. Wang
Keyword(s):  
Thin Films ◽  
Cyclic Voltammetry ◽  
Sol Gel ◽  
Gel Method ◽  
Sol Gel Method ◽  
Electrochemical Reversibility ◽  
Vis Spectroscopy ◽  
Ito Glass ◽  
Higher Temperature ◽  
Cv Measurements

NiO thin films were prepared on ITO glass by a modified sol-gel method in combination with a following annealing process. The XRD results show that the film annealed at 280 °C is amorphous, while the films annealed at and above 300 °C are cubic NiO phase. The electrochromic performances of the annealed films were characterized by means of UV–vis spectroscopy and cyclic voltammetry (CV) measurements. The film annealed at 280 °C exhibits a noticeable electrochromism with a variation of transmittance up to 76 % at 550 nm. The cyclic voltammetry (CV) measurements reveal that the film annealed at higher temperature has better electrochemical reversibility.

A biosensor consisting of Ca2Nb3O10− substrates and functional molecule manganese porphyrins (MnTMPyP) utilized for the determinations of nitrite

2018 ◽  
Vol 11 (03) ◽  
pp. 1850053 ◽  
Author(s):  
Jiasheng Xu ◽  
Bin Xia ◽  
Mengjun Wang ◽  
Zichun Fan ◽  
Xiaobo Zhang ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Ammonium Hydroxide ◽  
Differential Pulse ◽  
Colloidal Dispersion ◽  
Reduction Peak ◽  
Glass Carbon Electrode ◽  
Tetrabutyl Ammonium ◽  
Glass Carbon ◽  
The Stability ◽  
Cv Measurements

As functional molecules, the cationic manganese (III) tetrakis-5, 10, 15, 20-(N-methyl-4-pyridyl) porphyrins (MnTMPyP) were used to assemble with the exfoliated Ca2Nb3O[Formula: see text] nanosheets, which were obtained via treating the acidified compounds HCa2Nb3O[Formula: see text] of perovskite composites KCa2Nb3O[Formula: see text] with the tetrabutyl ammonium hydroxide (TBA[Formula: see text]OH[Formula: see text] aqueous solution. Several analytic techniques, such as XRD, SEM, TEM, FT-IR, UV-Vis, were employed to investigate the morphology and structure of KCa2Nb3O[Formula: see text], HCa2Nb3O[Formula: see text] and intercalation nanocomposites MnTMPyP/Ca2Nb3O[Formula: see text]. The stability and uniformity of the obtained Ca2Nb3O[Formula: see text] nanosheets colloidal dispersion were proved by the surface charge of [Formula: see text][Formula: see text]mV, which was obtained by a Zetasizer Nano instrument. Meanwhile, the electrochemical properties of MnTMPyP/Ca2Nb3O[Formula: see text] nanocomposites modified glass carbon electrode (GCE) was tested by using the cyclic voltammetry (CV) measurements and the differential pulse voltammetry (DPV) measurements. Results show that the intercalation nanocomposites have a good electrocatalysis towards oxidation of nitrite with a peak potential decrease from 1.125[Formula: see text]V to 0.916[Formula: see text]V. There is a good linear correlation between the reduction peak current and the square root of the scan rate, indicating a diffusion controlled process. In the end, an estimate of the detection limit was [Formula: see text][Formula: see text]M at a signal-to-noise ratio of 3.0 with a concentration range of [Formula: see text][Formula: see text]M to [Formula: see text][Formula: see text]M.

scholarly journals The effect of the presence of alcohol in the dispersing phase of oxide sols on the properties of RuO2-TiO4/Ti anodes obtained by the sol-gel procedure

2000 ◽  
Vol 65 (9) ◽  
pp. 649-660 ◽  
Author(s):  
V. Panic ◽  
A. Dekanski ◽  
S. Milonjic ◽  
R. Atanasoski ◽  
B. Nikolic
Keyword(s):  
Thermal Decomposition ◽  
Cyclic Voltammetry ◽  
Electrochemical Behaviour ◽  
Sol Gel ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Accelerated Stability ◽  
Chlorine Evolution Reaction ◽  
The Stability ◽  
Chloride Salts

The effect of the addition of ethanol and 2-propanol to the dispersing phase of TiO2 and RuO2 sols mixture on the morphology and, consequently, on the electrochemical properties of the sol-gel obtained activated titanium anodes was investigated. The properties of the obtained anodes were compared to those obtained by the thermal decomposition of appropriate chloride salts. The morphology of the anode coatings was examined by scanning tunneling microscopy. The electrochemical behaviour was investigated by cyclic voltammetry and by polarization measurements. An accelerated stability test was used for the examination of the stability of the anodes under simultaneous oxygen and chlorine evolution reaction. A dependence of the anode stability on the type of added alcohol is indicated.

scholarly journals Investigation of methanol electro-oxidation on graphene supported platinum–tungsten catalyst

Chemija ◽  
2019 ◽  
Vol 30 (3) ◽  
Author(s):  
Teofilius Kilmonis ◽  
Antanas Nacys ◽  
Dijana Šimkūnaitė ◽  
Loreta Tamašauskaitė-Tamašiūnaitė ◽  
Aldona Balčiūnaitė ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Molar Ratio ◽  
Heating Method ◽  
Molar Ratios ◽  
Microwave Assisted ◽  
Oxidation Of Methanol ◽  
Supported Platinum ◽  
Density Values ◽  
Electro Oxidation ◽  
Cv Measurements

The graphene (GR) supported platinum–tungsten (PtW) catalysts with Pt:W molar ratios, equal to 1.6:1, 2.3:1 and 7.1:1, were prepared by a rapid microwave-assisted heating method. The activity of the catalysts was investigated for the electro-oxidation of methanol in an alkaline medium by means of cyclic voltammetry (CV) and chronoamperometry (CA). It has been determined that the rate of methanol oxidation depends on the Pt:W molar ratio in the PtW/GR catalysts. From the CV measurements it follows that the highest current density values, specific and mass activities are obtained for the PtW/GR catalyst with the Pt:W molar ratio equal to 1.6:1. Similarly, the chronoamperometry measurements point to the best performance of the PtW/GR catalyst with the same Pt:W molar ratio. Moreover, in all cases the synthesized PtW/GR catalysts, regardless of different Pt:W molar ratio, show an enhanced electrocatalytic activity towards the direct electro-oxidation of methanol when compared with that for the bare Pt/GR and W/GR catalysts.

UV Curable Organic-Inorganic Hybrid Materials

2000 ◽  
Vol 628 ◽  
Author(s):  
Guang-Way Jang ◽  
Ren-Jye Wu ◽  
Yuung-Ching Sheen ◽  
Ya-Hui Lin ◽  
Chi-Jung Chang
Keyword(s):  
Hybrid Materials ◽  
Colloidal Silica ◽  
Sol Gel ◽  
Solution Ph ◽  
Uv Curable ◽  
Inorganic Hybrid ◽  
Degradation Temperature ◽  
Sol Gel Process ◽  
The Stability ◽  
Thermal Degradation Temperature

This work successfully prepared an UV curable organic-inorganic hybrid material consisting of organic modified colloidal silica. Applications of UV curable organic-inorganic hybrid materials include abrasion resistant coatings, photo-patternable thin films and waveguides. Colloidal silica containing reactive functional groups were also prepared by reacting organic silane and tetraethyl orthosilicate (TEOS) using sol-gel process. In addition, the efficiency of grafting organic moiety onto silica nanoparticles was investigated by applying TGA and FTIR techniques. Experimental results indicated a strong interdependence between surface modification efficiency and solution pH. Acrylate-SiO2 hybrid formation could result in a shifting of thermal degradation temperature of organic component from about 200°C to near 400°C. In addition, the stability of organic modified colloidal silica in UV curable formula and the physical properties of resulting coatings were discussed. Furthermore, the morphology of organic modified colloidal silica was investigated by performing TEM and SEM studies‥

The Stability of Steady-State Depth Distributions of Marine Phytoplankton

1974 ◽  
Vol 108 (963) ◽  
pp. 679-687 ◽  
Author(s):  
W. O. Criminale, ◽  
D. F. Winter
Keyword(s):  
Steady State ◽  
Marine Phytoplankton ◽  
The Stability ◽  
Depth Distributions

scholarly journals Suitability of the Cyclic Voltammetry Measurements and DPPH• Spectrophotometric Assay to Determine the Antioxidant Capacity of Food-Grade Oenological Tannins

Molecules ◽  
2019 ◽  
Vol 24 (16) ◽  
pp. 2925 ◽  
Author(s):  
Arianna Ricci ◽  
Giuseppina Paola Parpinello ◽  
Nemanja Teslić ◽  
Paul Andrew Kilmartin ◽  
Andrea Versari
Keyword(s):  
Cyclic Voltammetry ◽  
Colorimetric Assay ◽  
Radical Scavenging ◽  
Calibration Graph ◽  
Spectrophotometric Assay ◽  
Experimental Conditions ◽  
Fast Analysis ◽  
Cv Measurements ◽  
And Control ◽  
Analytical Approaches

Twenty commercially available oenological tannins (including hydrolysable and condensed) were assessed for their antiradical/reducing activity, comparing two analytical approaches: The 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging spectrophotometric assay and the cyclic voltammetry (CV) electrochemical method. Electrochemical measurements were performed over a −200 mV–500 mV scan range, and integrated anodic currents to 500 mV were used to build a calibration graph with (+)-catechin as a reference standard (linear range: From 0.0078 to 1 mM, R2 = 0.9887). The CV results were compared with the DPPH• assay (expressed as % of radical scavenged in time), showing high correlation due to the similarity of the chemical mechanisms underlying both methods involving polyphenolic compounds as reductants. Improved correlation was observed by increasing the incubation time with DPPH• to 24 h (R2 = 0.925), demonstrating that the spectrophotometric method requires a long-term incubation to complete the scavenging reaction when high-molecular weight tannins are involved; this constraint has been overcome by using instant CV measurements. We concluded that the CV represents a valid alternative to the DPPH• colorimetric assay, taking advantage of fast analysis and control on the experimental conditions and, because of these properties, it can assist the quality control along the supply chain.

scholarly journals Steady-state $$\dot{V}{\text{O}}_{2}$$ above MLSS: evidence that critical speed better represents maximal metabolic steady state in well-trained runners

2021 ◽  
Author(s):  
Rebekah J. Nixon ◽  
Sascha H. Kranen ◽  
Anni Vanhatalo ◽  
Andrew M. Jones
Keyword(s):  
Steady State ◽  
Critical Speed ◽  
Lactate Concentration ◽  
Practical Interest ◽  
Blood Lactate Concentration ◽  
Distance Runners ◽  
Severe Intensity ◽  
The Stability ◽  
Trained Runners ◽  
Over Time

AbstractThe metabolic boundary separating the heavy-intensity and severe-intensity exercise domains is of scientific and practical interest but there is controversy concerning whether the maximal lactate steady state (MLSS) or critical power (synonymous with critical speed, CS) better represents this boundary. We measured the running speeds at MLSS and CS and investigated their ability to discriminate speeds at which $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 was stable over time from speeds at which a steady-state $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 could not be established. Ten well-trained male distance runners completed 9–12 constant-speed treadmill tests, including 3–5 runs of up to 30-min duration for the assessment of MLSS and at least 4 runs performed to the limit of tolerance for assessment of CS. The running speeds at CS and MLSS were significantly different (16.4 ± 1.3 vs. 15.2 ± 0.9 km/h, respectively; P < 0.001). Blood lactate concentration was higher and increased with time at a speed 0.5 km/h higher than MLSS compared to MLSS (P < 0.01); however, pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 did not change significantly between 10 and 30 min at either MLSS or MLSS + 0.5 km/h. In contrast, $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 increased significantly over time and reached $$\dot{V}{\text{O}}_{2\,\,\max }$$ V ˙ O 2 max at end-exercise at a speed ~ 0.4 km/h above CS (P < 0.05) but remained stable at a speed ~ 0.5 km/h below CS. The stability of $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 at a speed exceeding MLSS suggests that MLSS underestimates the maximal metabolic steady state. These results indicate that CS more closely represents the maximal metabolic steady state when the latter is appropriately defined according to the ability to stabilise pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 .

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