Određivanje fizičko-hemijskih karakteristika ulja oraha (Juglans regia L.) sorte Šampion

The aim of this work was separation and determination of oil from the cultivar Šampion. Two techniques of oil extraction were employed: cold pressing and organic solvent extraction. Composition of walnut kernels and basic physico-chemical parameters of walnut oil were determined, respectively. The oil content was 69.07%. The fatty acid composition was determined by gas chromatography and the main components were as follows: linoleic acid 58.0%, oleic acid 20.7% and linolenic acid 9.8% for sample obtained by cold pressing and 60.9%, 19.0%, 13.6%, respectively, for sample obtained by solvent extraction.Danas se u svetu sve više pažnje posvećuje očuvanju prirodne i zdrave hrane. Zbog određenih zdravstvenih poremećaja i rizika, uslovljenih pre svega neadekvatnom ishranom, aktuelni svetski trendovi neminovno nameću novi koncept razvoja i u tehnologiji jestivih ulja. Povoljni zdravstveni efekti se pripisuju većem broju lipidnih supstanci, pri čemu se najveći broj radova i istraživanja odnosi na esencijalne masne kiseline, posebno one iz ω-3 i ω-6 serije, konjugovanu linolnu kiselinu, zatim fosfolipide, biljne sterole, prirodne antioksidanse i druge sastojke. Ulje oraha se odlikuje visokim sadržajem ω-6 i ω-3 esencijalnih masnih kiselina, što utiče na njegovu visoku nutritivnu vrednost. Upotreba orahovog ulja ima značajnu preventivnu ulogu u modifikaciji lipoproteinskog profila i zaštitnu ulogu kod kardiovaskularnih oboljenja i kancera. Istraživanja u ovom radu su imala za cilj da se uradi karakterizacija ulja oraha domaće sorte Šampion (Centar za voćarstvo, Čačak) i ispita uticaj postupka izdvajanja ulja na sadržaj esencijalnih masnih kiselina. Izdvojeno je ulje iz jezgra oraha domaće sorte Šampion primenom dve tehnike: hladno ceđenje i ekstrakcija organskim rastvaračem. Određeni su sastav i hemijske karakteristike jezgra oraha kao i fizičko-hemijske karakteristike izdvojenog ulja. Sadržaj ulja je iznosio 69.07%. Sastav i sadržaj masnih kiselina je određen metodom gasne hromatografije. Dominantne masne kiseline su: linolna sa sadržajem od 58.0%, zatim oleinska sa sadržajem od 20.7% i linolenska 9.8% u ulju dobijenom hladnim ceđenjem, odnosno 60.9%, 19.0%, 8.7% u ulju dobijenom ekstrakcijom organskim rastvaračem

Kinetics of the Hydrogen Oxidation on Pt Modified Moox Nano-Sized Catalyst in the Presence of Carbon Monoxide

Poster presented at the 11th Conference of the Materials Research Society of Serbia - YUCOMAT 2009, Herceg Novi, Montenegro, August 31 – September 4, 2009

On the kinetics of the hydrogen evolution reaction on zinc in sulfate solutions

The kinetics and mechanism of the hydrogen evolution reaction (her) were studied on zinc in 1.0 mol dm-3 Na2SO4 at 298 K, in the pH range 4.4 - 10. It was found that a combination of classical potentiostatic steady-state voltammetry (PSV) and electrochemical impedance spectroscopy (EIS) can help to elucidate dilemmas concerning the mechanism of this reaction. Thus, over the whole potential region, the reaction path of the her on zinc cannot be presented by the classical Volmer-Tafel-Heyrovsky route. It was found that the very complex S-shape of the polarization curves could be explained by two parallel reaction mechanisms for the her. The first reaction mechanism is a consecutive combination of three steps, in which the surface zinc oxide plays an active role in the her, and second reaction mechanism is a consecutive combination of a Volmer step, followed by a Heyrovsky step. The second mechanism is dominant in the more negative potential region where the active sites for the her are metallic zinc

Kinetics of the hydrogen oxidation on pt modified MoOx nano-sized catalyst in the presence of carbon monoxide

Due to the importance of the HOR in fuel-cells technology, various Pt-based catalysts have been examined from the viewpoint of immunity of the electrocatalysis of the HOR from CO-poisoning of the anode catalysts. An appreciable improvement of the CO tolerance has been found at Pt with adatoms such as Ru, Sn [1,2], Pt-M (M=Ru, Rh, Os, W Sn) [3-5] based alloys, and Pt with oxides (RuOxHy) [6]. In the present work, the electrocatalytic of home made highly dispersed nano-sized MoOx-Pt/C catalysts prepared by the polyole method combined by MoOx post-deposition was investigated in the presence of CO, in 0.5 moldm-3 HClO4 solution. The partial pressure of CO in CO/H2 gas mixture was 100 ppm. Carbon monoxide was adsorbed on the RDE for various time interval with keeping the potential at 0.05 V (RHE). The coverage of CO was determined by applying the first potential sweep (from 0.04 to 1.20 V), in N2 saturated solution at potential scan rate of 0.1 Vs-1 and compared it with the sweep on the clean electrode, by measuring the decrease in the hydrogen desorption charge, ΔQH. MoOx(20%)Pt/C catalyst exhibits an excellent CO tolerance, as it was found that the reduction in kinetic current, Ik, is negligible even at ΘCO = 0.46. It was found for this catalyst too, that the CO adsorption rate was much slower than that of Pt and the Pt sites for HOR were not so rigidly blocked by adsorbed CO partially due to its enhanced mobility, resulting from their modified electronic structure of surface Pt sites. Voltammetric studies suggest that an excellent CO tolerance of this catalyst could be also result of the oxidation of adsorbed CO to CO2 by oxophilic MoOx species at low overpotentials by a redox-mediated mechanism.Poster: [https://hdl.handle.net/21.15107/rcub_dais_266

Electrodeposition of NiMo alloy coatings and their characterization as cathodes for hydrogen evolution in sodium hydroxide solution

The hydrogen evolution reaction on electrodeposited NiMo alloy coatings, as well as their electrochemical properties in NaOH solutions have been investigated by polarization measurements, cyclic voltammetry and EIS technique. It is shown that NiMo alloy coatings electrodeposited from pyrophosphate-sodium bicarbonate bath possess high catalytic activity for hydrogen evolution in NaOH solutions. Their stability in 1M NaOH at 25 0C under the condition of reverse polarization is shown to be very good, while in 33% NaOH at 850C (conditions of industrial electrolysis) electrodeposited NiMo alloy coatings exhibit also high catalytic activity, but low stability, as a consequence of massive dissolution of alloy coatings under the condition of reverse polarization

Ni-MoO2 composite cathodes for hydrogen evolution in alkaline solution: Effect of aging of the electrolyte for their electrodeposition

In this work the effect of aging of the electrolyte for electrodeposition of Ni-MoO2 composite coatings on their morphology (scanning electron microscopy), chemical composition (energy-dispersive X-ray spectroscopy), polarization characteristics and the “service life” test performance for the hydrogen evolution reaction (HER) in 32 mass % NaOH at 90°C was investigated. Polarization characteristics and results of the “service life” test of Ni-MoO2 composite coatings obtained after different aging periods of the electrolyte for deposition (suspension of MoO2 powder particles in the solution containing 2 M NH4Cl + 0.2 M NiCl2) were compared with that recorded for De Nora’s commercial Ni+RuO2 cathode coating (DN). It was shown that aging of the electrolyte did not influence the morphology and chemical composition of Ni-MoO2 composite coatings electrodeposited under simulated conditions for their industrial production, while polarization characteristics for the HER were influenced. The best coating, obtained after 180 days of the electrolyte aging, showed completely different (layered) structure of the deposit and significantly better performance than the commercial DN electrode during the “service life” test. [Projekat Ministarstva nauke Republike Srbije, br. 172054

A novel platinum-based nanocatalyst at a niobia-doped titania support for the hydrogen oxidation reaction

The kinetics of the hydrogen oxidation reaction (HOR) was studied at Pt nanoparticles supported on niobia-doped titania (Pt/N-T). The catalyst support, with the composition of 0.05NbO2.5-δ-0.995TiO2 (0<δ<1), was synthesized by a modified sol-gel procedure and characterized by the BET and X-ray diffraction (XRD) techniques. The specific surface area of the support was found to be 70 m2 g-1. The XRD analysis revealed the presence of the anatase TiO2 phase in the support powder. No peaks indicating the existence of Nb-compounds were detected. Pt/N-T nanocatalyst was synthesized by the borohydride reduction method. Transmission electron microscopy revealed a quite homogenous distribution of the Pt nanoparticles over the support, with a mean particle size of about 3 nm. The electrochemical active surface area of Pt of 42±4 m2 g-1 was determined by the cyclic voltammetry technique. The kinetics of the HOR was investigated by linear sweep voltammetry at a rotating disc electrode in 0.5 mol dm-3 HClO4 solution. The determined value of the Tafel slope of 35 mV dec-1 and an exchange current density of 0.45 mA cm-2 per real surface area of the Pt are in good accordance with those already reported in the literature for the HOR at polycrystalline Pt and Pt nanocatalysts in acid solutions. This new catalyst exhibited better activity for the HOR in comparison with Pt nanocatalyst supported on Vulcan® XC-72R high area carbon

Korozioni aspekti nano-katalizatora na bazi plemenitih metala

U poslednjih deset godina došlo je do snažnog razvoja različitih tipova gorivnih spregova kao što su: spregovi sa čvrstim polimernim elektroltima visoko-temperaturni gorivni spregovi, spregovi sa čvrstim elektrolitima na bazi oksida metala, fosforni gorivni spregovi itd. Ovaj razvoj je pre svega ostvaren primenom nanokatalizatora. U navedenim gorivnim spregovima koriste se katalizatori na bazi plemenitih metala, pre svega platina l njene legure gde srednja veličina čestica varira u opsegu od 2 - 5 nm, čime se ostvaruje izuzetno velika specifična površina katalizatora u opsegu od 20 do 120 m2/g a time i visoka radna gustina struje, po geometrijskoj površini elektrode (~ 1 A / cm2)

Ni-(Ebonex-supported Ir) composite coatings as electrocatalysts for alkaline water electrolysis. Part I: Hydrogen evolution

The hydrogen evolution reaction (HER) was studied at electrodeposited Ni and Ni-(Ebonex/Ir) composite coatings in 1 mol dm-3 NaOH solution at 25 °C. The Ni-(Ebonex/Ir) coatings were electrodeposited from a nickel Watts type bath containing different amounts of suspended Ebonex/Ir(30 wt.%) powder particles (0-2 g dm-3) onto a Ni 40 mesh substrate. The electrodes were investigated by cyclic voltammetry (CV), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), electrochemical impedance spectroscopy (EIS) and polarization measurements. It was shown that the roughness factor of coatings increased to a maximum value of 27 with increasing the concentration of Ebonex/Ir particles in the deposition bath, while that of a pure Ni coating was found to be 3.2. In the whole potential range of the HER only one Tafel slope of about -120 mV dec-1 was observed at all polarization curves. Considerably improved intrinsic catalytic activity for the HER compared to pure Ni was achieved with the composite coating deposited from the bath with the lowest concentration of Ebonex/Ir particles (0.1 g dm-3). Further enhancement of the apparent catalytic activity for the HER of Ni-(Ebonex/Ir) composite coatings obtained at higher concentrations of suspended Ebonex/Ir particles in the bath was attributed only to the increase of their electrochemically active surface area. © 2015 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved

On the kinetics of the hydrogen evolution reaction on Ni-MoOx composite catalysts in alkaline solutions

MoO3 particles were co-deposited with Ni onto smooth or rough Ni supports from modified Watt’s baths of different compositions. Morphology and composition of the electrodeposits were characterized by means of cyclic voltammetry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The electrocatalytic activity of the composite catalysts for H2 evolution in alkaline solutions was determined by quasi-stationary polarization curves. Activity increases with MoOx content in the Ni deposit up to a limiting value. Composite Ni-MoOx catalyst performed high catalytic activity, similar to that of commercial Ni-RuO2 catalyst. Stability tests showed that Ni-MoOx codeposits are stable under condition of constant current and exhibit excellent tolerance to repeated short-circuiting