Effect of electrochemical oxidation of glassy carbon on deposition of platinum particles and electrocatalytic activity of platinum supported on oxidized glassy carbon (Pt/GC
OX) were studied for ...methanol oxidation in H
2SO
4 solution. Platinum was potentiostatically deposited from H
2SO
4
+
H
2PtCl
6 solution. Glassy carbon was anodically polarised in 0.5 M H
2SO
4 at 2.25 V vs. saturated calomel electrode (SCE) during 35 s. Electrochemical treatment of GC support, affecting not significantly the real Pt surface area, leads to a better distribution of platinum on the substrate and has remarkable effect on the activity. The activity of the Pt/GC
OX electrode for methanol oxidation is larger than polycrystalline Pt and for more than one order of magnitude larger than Pt/GC electrode. This increase in activity indicates the pronounced role of organic residues of GC support on the properties of Pt particles deposited on glassy carbon.
Formic acid oxidation was examined on platinum-bismuth deposits on glassy carbon substrate prepared by two-step process, i.e., electrochemical deposition of Bi followed by electrochemical deposition ...of Pt as described in our previous article (J Electrochem Soc 161:H547–H554,
2014
). Upon treatment of as-prepared clusters by slow anodic sweep, bimetallic structure consisting of Bi core occluded by Pt and Bi-oxide was obtained and exhibited significant activity and exceptional stability in HCOOH oxidation. In order to explain such electrocatalytic stability, in this work, the electrochemical properties of Pt@Bi/GC catalyst were investigated applying same protocols in supporting electrolyte with or without HCOOH and compared with Pt/GC. The protocols comprised potentiodynamic, quasi-steady-state, and chronoamperometric measurements combined with the surface characterization by CO
ads
stripping voltammetry. Application of potential cycling at Pt@Bi/GC electrode in supporting electrolyte containing HCOOH leads to minor change in surface morphology, mildly leaching of Bi from the electrode surface, and negligible decrease in activity. On the other hand, significant Bi dissolution and considerable decrease in activity are the effects of the same treatment without HCOOH. Contrary to Pt@Bi/GC, Pt/GC electrodes subjected to the same protocols exhibit completely opposite properties being more stabile during potential cycling without HCOOH than in the presence of this acid. Exceptional stability in formic acid oxidation of Pt@Bi/GC catalyst is thus most probably the result of the combination of predominant dehydrogenation path of the reaction, suppressed Bi leaching, and compensation of dissolved Bi from the core as its source due to which surface morphology endured minor changes.
The aim of this study was to compare the effects of caffeine, caffeine-taurine combination and placebo on selective attention. The sample consisted of 26 medical students, an equal number of females ...and males. The study was performed as a single-blind trial, using the Latin square design. The students solved PEBL Stroop test, which tested interference effects between different types of information: color and word. The students completed Spielberger’s test of anxiety (STAI Y). General linear model with repeated measures showed that reaction times for consistent, conflict and single feature stimulus conditions were significantly different (F(27.395) = 1.910, p = 0.005) under the different experimental condition. Univariate Tests showed the effects of caffeine ( F = 3.793, p = 0.026) and combination of caffeine and taurine ( F = 3.162, p = 0.056), but did not find effects of placebo condition ( F = 0.808, p = 0.503) for different Stroop tasks. The effect of treatment was found for consistent, conflict and single feature condition, either for name or color condition, but facilitation and cost effects were found only for color condition. The trait and state anxiety did not have effects on selective attention. Caffeine individually, as well as combined with taurine showed different effects on selective attention compared to placebo condition.
The electrochemical oxidation of methanol, ethanol,
n-propanol and
n-butanol has been carried out at the Pt(111) and the stepped Pt(755) and Pt(332) surfaces in sodium hydroxide solution. Special ...attention was paid to the study of the oxygen-containing species generated and adsorbed during surface oxidation. The existence of reversible OH
ad, irreversible OH
ad and PtO species was suggested in the potential region relevant for the alcohol oxidation. The role of these species in the reaction was determined and a dual path mechanism was proposed for the alcohols studied.
The electrocatalytic activity of Pt3Ru2/C nanocatalyst toward the electro-oxidation of bulk CO was examined in acid and alkaline solution at ambient temperature using the thin-film, rotating disk ...electrode (RDE) method. The catalyst was characterized by XRD analysis. The XRD pattern revealed that the Pt3Ru2/C catalyst consisted of two structures, i.e., Pt-Ru-fcc and Ruhcp (a solid solution of Ru in Pt and a small amount of Ru or a solid solution of Pt in Ru). Electrocatalytic activities were measured by applying potentiodynamic and steady state techniques. The oxidation of CO on the Pt3Ru2/C catalyst was influenced by pH and anions from the supporting electrolytes. The Pt3Ru2/C was more active in alkaline than in acid solution, as well as in perchloric than in sulfuric acid. Comparison of CO oxidation on Pt3Ru2/C and Pt/C revealed that the Pt3Ru2/C was more active than Pt/C in acid solution, while both catalysts had a similar activity in alkaline solution.
Elektrohemijska oksidacija CO ispitivana je na nanokatalizatoru Pt3Ru2 dispergovanom na aktivnom uglju kao nosacu u kiseloj i alkalnoj sredini na sobnoj temperaturi koriscenjem metode rotirajuce disk elektrode (RDE). Katalizator je okarakterisan difrakcijom X-zraka (XRD) i dobijeni rezultati su pokazali da se legura Pt3Ru2 sastoji od dve faze: cvrstog rastvora Ru u Pt i od malih kolicina cistog Ru ili cvrstog rastvora Pt u Ru. Elektrokataliticka aktivnost ovog katalizatora za oksidaciju CO je ispitivana cik- licnom voltametrijom i pokazan je efekat pH i efekat anjona iz noseceg elektrolita. Pt3Ru2/C katalizator je aktivniji u alkalnoj nego u kiseloj sredini, ukazujuci na cinjenicu da u alkaliji Pt moze da adsorbuje OH cestice na isto tako niskim potencijalima kao i Ru i na taj nacin ubrzava reakciju oksidacije CO u poredjenju sa kiselinom. Pokazano je da adsorpcija bisulfatnih anjona iz noseceg elektrolita pomera pocetni potencijal reakcije ka pozitivnijim vrednostima i smanjuje brzinu oksidacije CO. Poredjenjem aktivnosti Pt/C i Pt3Ru2/C katalizatora u oksidaciji CO u kiseloj i alkalnij sredini pokazano je da je ta razlika znatno manja u alkalnoj nego u kiseloj sredini.
The Covid-19 pandemic caused a shutdown of healthcare systems in many countries. We explored the impact on hypertension care in the Excellence Center (EC) network of the European Society of ...Hypertension.
We conducted a 17-question electronic survey among ECs.
Overall, 52 ECs from 20 European and three non-European countries participated, providing hypertension service for a median of 1500 hypertensive patients per center per year. Eighty-five percent of the ECs reported a shutdown lasting for 9 weeks (range 0-16). The number of patients treated per week decreased by 90%: from a median of 50 (range 10-400) before the pandemic to a median of 5.0 (range 0-150) during the pandemic (P < 0.0001). 60% of patients (range 0-100%) declared limited access to medical consultations. The majority of ECs (57%) could not provide 24-h ambulatory BP monitoring, whereas a median of 63% (range 0-100%) of the patients were regularly performing home BP monitoring. In the majority (75%) of the ECs, hypertension service returned to normal after the first wave of the pandemic. In 66% of the ECs, the physicians received many questions regarding the use of renin-angiotensin system (RAS) blockers. Stopping RAS-blocker therapy (in a few patients) either by patients or physicians was reported in 27 and 36.5% of the ECs.
Patient care in hypertension ECs was compromised during the Covid-19-related shutdown. These data highlight the necessity to develop new strategies for hypertension care including virtual clinics to maintain services during challenging times.
Formic acid oxidation was studied on a new prepared Pt
2
Bi characterized by X-ray diffraction spectroscopy (phase composition), scanning tunneling microscopy (STM) (surface morphology), and CO
ads
...stripping voltammetry (surface composition). Bulk composition of Pt
2
Bi revealed two phases—55% PtBi alloy and 45% Pt. Estimated contribution of pure Pt on the Pt
2
Bi surface (43.5%) determined by CO
ads
stripping voltammetry corresponds closely to bulk composition. Pt
2
Bi reveals high activity and stability in formic acid oxidation. High activity originates from the fact that formic acid oxidation proceeds completely through dehydrogenation path based on an ensemble effect. The high stability of Pt
2
Bi surface is induced by the suppression of Bi leaching as it was evidenced by insignificant changes of surface morphology and surface roughness shown by STM images before and after electrochemical treatment in formic acid containing solution. Pt
2
Bi is found to be powerful catalyst exhibiting up to two orders of magnitude larger current densities at 0.0 V and onset potential shifted for ∼0.2 V to more negative value relative to Pt under steady-state condition.
The method to develop a stable glucose biosensor with successive attachment of cysteine (Cys), glutaraldehyde (GA) and glucose oxidase (GOx) onto gold electrode is presented. The cyclic voltammetry ...(CV) suggests the diffusion control of the glucose oxidation. The obtained biosensor shows a fast electron transfer of k0 = 20.4 s-1, high affinity for glucose with the apparent Michaelis-Menten constant KMapp= 1.15 mM, a low detection limit of 0.94 mM in a linear range 1.5-7 mM. This biosensor exhibits good stability and reproducibility. Good biocompatibility of modified electrode surface, which enhances the covalent bonded enzyme and consequently glucose oxidation, resulted in biosensor with excellent performances. Biosensor was tested in samples containing human serum.
The oxidation of ethanol was studied at Snad-, Ruad- and Rhadmodified and
unmodified PtC, Pt3Sn/C and Pt3Ru2/C catalysts. Potentiodynamic,
quasi-steady-state and chronoamperometric measurements were ...used to
investigate the activity and stability of the catalysts. Irreversible
adsorption of a small amount of each of the adatoms (?10 % surface coverage)
enhanced the activity of the Pt/C and Pt3Sn/C catalysts. The onset potential
was shifted by ?50 mV towards lower values and the current densities over the
whole studied potential region were up to two times higher with respect to
the unmodified catalysts. On the other hand, the addition of Snad or Rhad
slightly increased the activity of Pt3Ru2/C, while the presence of Ruad
decreased its activity for ethanol oxidation. The catalytic action of Snad
and Ruad was associated mostly with their ability to adsorb oxygen-containing
species at lower potentials than Pt, permitting a bifunctional mechanism to
proceed. Rhad also acted on the C-C bond breaking activation as well as
source of oxygen containing species, increasing in this way the activity of
the modified surfaces for ethanol oxidation.
nema
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