Differential Capacity of Bromide Anions Adsorption onto Ag(100) in the Absence, and onto Ag(poly) in the Presence of NaClO4

In this work, the adsorption of bromide anions onto Ag(100) and Ag(poly) in the absence and presence of NaClO4 was investigated. The cyclic voltammetry, EIS and Cdiff vs. E measurement results were analyzed. For the determination of the adsorption parameters, the equivalent circuit containing constant phase element (CPE) instead of the double layer capacity (Cdl) and new equations for the analysis of the anion adsorption, based on a different definition of the CPE, have been developed and used. It was shown that the proposed equivalent circuit and corresponding equations for the differential capacity (Cdiff) as a function of frequency (ω) can successfully be applied in the investigated systems. Excellent agreement between the cyclic voltammograms (CVs) and the Cdiff vs. E curves recorded at frequencies lower than 10 Hz has been detected. The homogeneity of the charge distribution over the real single crystal surfaces, as well as other parameters of the adsorption process were found to change with the potential. In the presence of the supporting (“non-adsorbing”) electrolyte (0.1 M NaClO4) diffusion-like phenomenon was detected and ascribed to the slow step in exchanging anions adsorbed in the inner Helmholtz plane

Electrodeposition of cobalt powders with novel three-dimensional structure

Novel three-dimensional cobalt powder structures were successfully prepared by electrodeposition. Electrodeposited cobalt powder was characterized by scanning electron microscopy (SEM) and light microscopy. It was possible to control the morphology and structure of cobalt particles by adjusting process parameters of electrodeposition such as current density and type of working electrode. The morphology and structure of cobalt powders were investigated and the formation mechanism of agglomerate was also discussed

Corrected accelerated service life test of electrodeposited NiSn alloys and Ni as cathodes for industrial alkaline water electrolysis

The "corrected accelerated service life test for hydrogen evolution reaction" (CASLT-HER), designed for application of certain electrode materials as cathodes in the cell for alkaline water electrolysis in 30 % KOH at 80 degrees C, was performed at electrodeposited NiSn alloy and Ni 40 mesh electrodes. The Ni 40 mesh was slightly etched, while the NiSn alloy coating was electro-deposited from the bath containing pyrophosphate, glycine, SnCl2 and NiCl2 onto Ni 40 mesh to the thickness of approximately 40 mu m. It is shown that the NiSn cathode possess from maximum 0.77 V to minimum 0.30 V better over-potential than the Ni 40 mesh electrode during the 5 years of their exploitation at the conditions of industrial alkaline water electrolysis. It is also shown that both electrodes should be held at j = -0.3 A cm(-2) for at least 5 h in order to establish stable overpotential response. The limiting overpotential values for applying cyclic voltammetry (CVs, to mimic "polarity inversion") should be determined in a separate experiment before the CASLT-HER and should be adjusted during the application of CVs

Izračunavanje prave vrednosti kapaciteta dvojnog sloja iz konstantnog faznog elementa u impedansnim merenjima

Considering literature of electrochemical impedance spectroscopy (EIS) it was discovered that for calculation of the value of double layer capacitance (Cdl) from the constant phase element (CPE) two equations, with or without solution resistance (Rs) could be used. After calculation of Cdl for defined values of CPE constant Ydl, CPE exponent , Rs and charge transfer resistance (Rct), it was confirmed in this work that different results for Cdl were obtained by including Rs in the calculation of Cdl. It was also stated that “it is quite difficult to understand how both parameters (Rct and Rs) could be expressed by the same time constant, i.e. the same parameter .” By investigating the hydrogen evolution reaction (HER) at Ni mesh 40 electrode in the solution of 1 M KOH at 25 oC using EIS measurements, it was shown that different Cdl vs. E plots were obtained using these two equations for Cdl calculation. A simple solution to avoid this problem with detailed explanation, the use of equation without Rs, has been suggested in this work.Razmatrajući literature o elektrohemijskoj impedansnoj spektroskopiji (EIS) ustanovljeno je da za izračunavanje vrednosti kapaciteta dvojnog sloja (Cdl) iz konstantnog faznog elementa (CPE) postoje dve jednačine, jedna u kojoj figuriše otpor elektrolita (Rs) i druga u kojoj ovaj parametar ne figuriše. Izračunavanjem vrednosti Cdl za definisane parametre (Ydl, , Rs, Rct), u ovom radu je pokazano da se dobijaju drugačiji rezultati za Cdl primenom ovih jednačina. Takođe je konstatovano da je neprihvatljivo da oba parametra (Rct i Rs) na isti način zavise od vremenske konstante, odn. od parametra . Ispitivanjem reakcije izdvajanja vodonika na Ni mrežici u rastvoru 1 M KOH na 25 oC korišćenjem impedansnih merenja, pokazano je da su zavisnosti Cdl vs. E, dobijene korišćenjem pomenutih jednačina, različite. Da bi se izbegao ovaj problem predloženo je da se koristi jednačina u kojoj ne figuriše otpor elektrolita (Rs), jer uvodjenje Rs nema korektan fizički smisao

Mehanizam i kinetika elektrosorpcije sulfatnih anjona na (111) pljosni srebra

The processes of adsorption of sulphate anions onto the (111) face of silver have been investigated by analysis of the cyclic voltammetry and potcntiostatic pulse results. It was shown, by fitting the experimentally recorded θ - E dependences, that the adsorption of anions follows Frumkin adsorption isotherm. The adsorbed structure was found to be less dense than expected for the dense packed anion monolayer and the process was characterized by high value of the interaction parameter and the Gibbs energy of adsorption (f = 16.5 and ΔGoads.θ→0 = - 64 kJ mol 1). From the slope of the Ep.a - log (c0) dependence it was concluded that complete charge transfer between the adsorbed anions and the silver substrate occurs. This is supported by the Ep.a - log v linear dependence in the region of high sweep rates (v > 10 V s 1) with rational value of line slope (≈ 60 mV dec 1) which is possible only if the complete charge transfer reaction occurs. The elcctrosorption process of sulphate anions was found to be complex electrochemical reaction, taking place through three steps. It was proposed that the rate-determining step is the second step, i.e., the electrochemical formation of (SO4)ads species.Proučavan je proces adsorpcije sulfatnih anjona na (111) pljosni monokristalasrebra metodama ciklične voltametrije i potenciostatskih pulseva. Na osnovu eksperimentalno određenih q–E zavisnosti pokazano je da se na adsorpciju može primeniti Frumkinova adsorpciona izoterma. Nađeno je da je gustina adsorbovanog slojamanja nego kada bi sloj bio maksimalno moguće gusto pakovan kao i da adsorpcijukarakterišu visoke vrednosti Frumkinovog parametra interakcije (f = 16,5) i Gibsoveenergije adosrpcije (DGºads,q®0 = –64 kJ mol). Na osnovu nagiba zavisnosti Ep,a –log (c0)zaključeno je da se pri elektrosorpciji odigrava i potpuna izmena naboja anjona sasupstratom. Ovaj zaključak podržava dobijena linearna zavisnost Ep,a – log v u oblastivelikih brzina promene potencijala (v>10 V s–1) sa racionalnom vrednošću nagiba (»60mV dek–1), a koja se može dobiti samo pri odigravanju potpune razmene naboja. Utvrđenoje da je elektrosorpcija sulfatnih anjona složena elektrohemijska reakcija koja seodigrava u tri stupnja. Stupanj koji određuje brzinu ukupne reakcije je drugi stupanj,elektrohemijsko stvaranje intermedijera (SO4)ads

REVITALIZE AND REPOSITION INDONESIAN PUBLIC ADMINISTRATION, THE LEGACY OF LAW

Tulisan ini mencoba menggunakan pendekatan atau perspektif historis dalam upaya untuk mencari model yang asli untuk pelaksanaan otonomi daerah. Dengan pendekatan historis ditelusuri pelaksanaan administrasi publik yang bersumber dari adat istiadat Jawa, masa pemerintahan Hindia Belanda dan Masa Republik pada tahun 1945. Pendekatan administrasi yang digunakan dalam adat istiadat Jawa adalah konsensus dan dekrit. Dalam pemerintahan Hindia Belanda terjadi penggabungan antara adat-istiadat dengan berbagai ketentuan yang dikembangkan oleh Belanda. Dalam era Republik terjadi tarik menarik antara peraturan yang bersifat positivisme dan romantisme. Model yang diajukan adalah adanya kombinasi antara adat, peraturan yang berlaku dalam masa kolonial dan peraturan yang dihasilkan dari penguasa yang ada sekarang ini

Electrodeposition and characterization of Fe-Mo alloys as cathodes for hydrogen evolution in the process of chlorate production

Fe-Mo alloys were electrodeposited from a pyrophosphate bath using a single diode rectified AC current. Their composition and morphology were investigated by SEM, optical microscopy and EDS, in order to determine the influence of the deposition conditions on the morphology and composition of these alloys. It was shown that the electrodeposition parameters, such as: chemical bath composition and current density, influenced both the composition of the Fe Mo alloys and the current efficiency for their deposition, while the micro and macro-morphology did not change significantly with changing conditions of alloy electrodeposition. It was found that the electrodeposited Fe Mo alloys possessed a 0.15 V to 0.30 V lower overvoltage than mild steel for hydrogen evolution in ail electrolyte commonly used in commercial chlorate production, depending on the alloy composition, i.e., the conditions of alloy electrodeposition

Interfacial Polarization and Dielectric Properties of Epoxy/Graphite Flakes Composites

Dielectric properties of composites based on bisphenol-A-epoxy resin loaded with various content of graphite flakes (GF) have been studied. The dielectric permeability, tangent loss and ac conductivity have been examined in wide temperature (170 – 370 K) and frequency (20 Hz – 200 kHz) range. In composites loaded with GF flakes up to 10 wt.%, the dominant conduction mechanism is tunneling of electrons, while loading of 15 wt.% gives rise to electron conduction through direct contacts between fillers. Dielectric properties of composites are largely determined by the nature of the filler/matrix interface, the filler surface area and the inherent conductivity of the fillers. At low electric field frequencies, dominates socalled interfacial (or space charge) polarization due to accumulation of free charges at the interfaces between two phases (filler and matrix), which differ in electrical conductivity.Influence of the filler surface chemistry have been studied for composites loaded with 5 wt.% graphite flakes obtained: (i) under wet milling, without (GF) or with (GF-Tr100x) adding Triton-100x as a surfactant, or (ii) under dry milling in the presence of KOH (GF-KOH). The surface treatment with KOH notable increased dielectric constant of the epoxy/GF-KOH5 composite, keeping low tangent loss, comparable to the counterpart, the epoxy/GF5 composite

Morphology of Different Electrodeposited Pure Metal Powders

As mentioned in other chapters, metal powders obtained by electrolytic processes are mainly dendrites which can spontaneously fall off or can be removed from the electrode by tapping or other similar techniques [1]. Also, powder particles can have other morphological forms, such as flakes or needles, fibrous or spongy, and needle or cauliflower-like ones, and the shape of powder particles depends on the electrodeposition conditions and the nature of the metal.This is the author's version of the accepted, peer-reviewed manuscript: Jović V.D., Nikolić N.D., Lačnjevac U.Č., Jović B.M., Popov K.I. (2012) Morphology of Different Electrodeposited Pure Metal Powders. In: Djokić S. (eds) Electrochemical Production of Metal Powders. Modern Aspects of Electrochemistry, vol 54. Springer, Boston, MA. [https://doi.org/10.1007/978-1-4614-2380-5_2]The published version: [https://cer.ihtm.bg.ac.rs/handle/123456789/4092

Determination of Marine Pollution By Comparative Analysis of Metal Pollution Indices

Due to the specific geographical and hydrological structure of Boka Kotorska Bay, that is characterized by a low flow of water through the bay, the anthropogenic impact is pronounced, exerting direct effects on this unique ecosystem. Trace metal (Pb, Hg, Ni, Co and Cd) concentrations were measured in the winter, spring and fall of 2008 in two marine organisms (Posidonia oceanica and Mytilus galloprovincialis) selected as biomonitors of trace metals in the Boka Kotorska Bay. These marine organisms have the ability to accumulate trace metals from their environment. Metal pollution indexes (MPI) for both species were compared, confirming that the most polluted was Tivat bay and the least Kotor bay