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Download Free PDFEffect of the pH value of the hydrogenation solution upon the phase transformation of nickel into nickel hydrideMilko Monev

2001, Electrochimica Acta

https://doi.org/10.1016/S0013-4686(01)00438-8visibility

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Abstract

The effect of pH value of the hydrogenation solution, containing H 2 SeO 3 as a hydrogenation-enhancing additive upon the phase transformation of nickel into b-nickel hydride in electrodeposited bright nickel coatings during cathodic charging was studied using X-ray diffraction. The nickel hydride formation terminates at pH value over 2.1. At this pH value in the bulk of hydrogenation solution, the pH value within the layer in the vicinity of the nickel electrode shift during the cathodic process to the alkaline region as a result of hydrogen evolution. An indication of the alkalization is the shift of the nickel electrode potential towards more negative values ( − 1.3 V NHE) within the range of pH values where phase transformation terminates. The hydrogenation enhancing effect of H 2 SeO 3 appears to occur when the deposition of selenium on nickel surface begins. Strong hydrogenation of samples with co-deposited selenium proceeds during cathodic polarization in an acidic medium without an enhancing additive.

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Key takeaways

AI

1. Nickel transforms into b-nickel hydride at pH values below 2.1 during cathodic polarization.
2. Hydrogenation enhancement by H2SeO3 occurs when selenium deposition begins on nickel surface.
3. Maximum hydrogen solubility in steel occurs around pH 2, reducing at higher pH.
4. X-ray diffraction confirms phase transformation and potential shifts indicate alkalization during charging.
5. Understanding pH's role in hydrogen evolution reactions is critical for optimizing electrochemical processes.

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downloadDownload free PDFView PDFchevron_rightNew hydrogen cathodes in acid medium: Case of nickel electrodeposited with heteropolyacids (HPAs)Oumarou SAVADOGO

International Journal of Hydrogen Energy, 1990

AMtraet--The electrodeposition of nickel from different baths with and without heteropolyacids (HPAs) was performed. Different electrodes have been checked: electrodeposited nickel from baths without HPAs (Ni); activated Ni at the surface with HPAs (NiAHPAs) and electrodeposited nickel from baths containing HPAs (NiHPAs). The HPAs are SiWt204-and PWi20~0-. A study was carried out to investigate the influence of the HPAs on the electrocatalytic properties of the hydrogen evolution reaction (h.e.r.) on these electrodes. An important decrease of the overpotential 0/) and a significant increase of the exchange current density (io) for the h.e.r, were obtained. The nickel electrode prepared with PWt20~ 0-is more electroactive than Pt for the h.e.r, in acid medium. Further, NiHPAs is more active than NiAHPAs for the h.e.r. On the other hand, NiHPAs are less sensitive to impurity effects than Pt for the h.e.r.

downloadDownload free PDFView PDFchevron_rightElectrochemical studies of a nickel electrode for the hydrogen evolution reactionALTAF KHAN

International Journal of Hydrogen Energy, 1995

The mechanism of the hydrogen evolution and reduction reactions on a nickel electrode has been examined several times, mainly because of the potential application of this material in water electrolysers and fuel cells. This work presents the results of electrochemical studies of hydrogen evolution and reduction on nickel plate in 30 wt% KOH at different temperatures ranging from 28 to 77-C. Kinetic parameters were obtained by steady state polarization experiments, compleme@d by cyclic voltammetry. Nickel showed an improved performance with increaGng temperature. It has been observed that a temperature increase from 28 to 77'C results iq an almost equal Tafel slope of 80 mV dcc-*. This bchaviour could be the impact of such factors as variation of the adsorbed hydrogen coverage with potential or the entropic contribution to the free energy of activation. However, some controversy still remains. Current density values increase with increasing temperature. A current-time dependence curve shows that the current density is constant up to 200 s, then it decreases with time. However, after loo0 s, current density is again constant and remains so up to 3000s. The apparent energy of activation AH was calculated from the Arrhenius plot.

downloadDownload free PDFView PDFchevron_rightHydrogen evolution on nickel electrode in synthetic tap water – alkaline solutionFrank de Bruijn

Fuel and Energy Abstracts, 2011

The effect of tap water contaminants on the kinetics of the hydrogen evolution reaction on a nickel electrode in 1 mol dm−3 KOH was investigated by galvanostatic polarization and electrochemical impedance spectroscopy techniques. It was found that the tap water contaminants lead to an increase in the overpotential of the hydrogen evolution reaction, especially at low temperatures. The combination of electrochemical techniques, as well as physicochemicals such as SEM and EDAX ones, confirmed that the contaminants are specifically adsorbed and blocked the available electrode surface for the reaction. It was concluded that they do not participate in an electrochemical reaction in the potential region where HER occurs. Besides the short term negative impact on the rate of hydrogen evolution, a 55 h test revealed that the overpotential shows a steady increase over time in presence of tap water contaminants, while in absence of these contaminants the overpotential is constant.► Influence of the contaminants in simulated tap water on the hydrogen evolution. ► The mechanism of the reaction is the same as in purified water. ► Contaminants do not take place in the electrochemical reaction. ► Adsorption of anions on the electrode surface leads to increase of the overpotential. ► Gas phase product is the same as the one obtained from purified water.

downloadDownload free PDFView PDFchevron_rightImproved performance of a metal hydride electrode for nickel/metal hydride batteries through copper-coatingD. Northwood

Surface and Coatings Technology, 2003

Four important properties (exchange current density, apparent activation energy, high-rate dischargeability and discharge potential) were studied for a LaNi Al metal hydride (MH) electrode fabricated using alloy powders coated with copper. A 4.7 0.3 half-cell setup was employed with a 6 M KOH electrolyte solution. The results are compared with those for a similar electrode without the Cu-coating. The exchange current density and apparent activation energy for the MH electrode reaction have been evaluated using the potentiodynamic method. The Cu-coated powder electrode showed improved performance, i.e., a higher exchange current density, larger high-rate dischargeability and lower discharge potential, compared to the electrode made with uncoated alloy powder. Thus, Cu-coating ensures both stable discharge performance and high specific power of a NiyMH battery. This improvement may be due to the following two reasons: (i) corrosion or oxidation protection of alloy powders; (ii) decrease in contact resistance. There is no significant difference between the two apparent activation energies for the electrode reactions for the electrodes with and without the Cu-coating at the same hydrogen concentration.

downloadDownload free PDFView PDFchevron_rightElectrodeposited, Ni-based, non-noble metal coatings as cathodes for hydrogen evolution in chlor-alkali electrolysisUroš Lačnjevac

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The hydrogen evolution reaction (HER) has been investigated on two types of electrodeposited, Nibased, non-noble metal coatings: composite coatings with inclusion of MoO2 particles and electrodeposited NiSn alloy coatings, in order to find suitable replacement for noble metal coatings (commercial De Nora's Ni-RuO2 electrode (DN)), as cathodes for industrial application in the zero-gap membrane cell for chlor-alkali electrolysis. Some samples of both types of cathodes showed better catalytic activity for the HER than the DN electrode under the conditions of industrial applications: 32 mass % NaOH at 90 o C and j = -0.3 A cm -2 . Since lower overvoltage for the HER is not the only criteria for successful application in industrial electrolysis, service life test (SLT), simulating long time operation of cathodes, has been applied for both types of cathodes. It has also been shown that certain samples of both types of cathodes could be promising replacement for the commercial DN electrode since they showed better performance during the SLT.

downloadDownload free PDFView PDFchevron_rightEffect of Versenium Hydrogensulfate on Properties of Nickel CoatingsMagdalena Regel-Rosocka

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The salt of formula [H2EDTA2+][HSO4−]2 (dihydrogen ethylenediaminetetraacetate di(hydrogen sulfate(VI)) was used to examine the physicochemical properties of the resulting Ni layer and evaluate the applicability of the salt as a new additive for Watts-type baths. The Ni coatings deposited from baths containing [H2EDTA2+][HSO4−]2 were compared with those obtained from other baths. The nucleation of nickel on the electrode was proven to occur the slowest in the bath that contained the mixture of [H2EDTA2+][HSO4−]2 and saccharin compared with other baths. The addition of [H2EDTA2+][HSO4−]2 alone (bath III) generated a coating with a morphology similar to that obtained from bath I (without additives). Despite the similar morphology and wettability of the Ni-coated surfaces plated from various baths (all Ni coatings were hydrophilic with contact angles in the range of 68 to 77°), some differences in electrochemical properties were noted. The corrosion resistance for the coatings plated f...

downloadDownload free PDFView PDFchevron_rightNickel–cobalt electrodeposited alloys for hydrogen evolution in alkaline mediaAlessandro Dell'Era

International Journal of Hydrogen Energy, 2009

A study on the electrocatalytic performances of nickel-cobalt alloys for hydrogen evolution in alkaline media has been carried out. After preparing, by electrodeposition on aluminium net supports, Ni-Co alloys of various compositions ranging from 0 to 100% Ni, the alloys were examined by polarization measurements, to evaluate their discharge potential and Tafel parameters. Moreover a durability test has been done on the alloys showing, among all, the best performance. The hydrogen over-potential appears to be lower in the case of Ni concentrations ranging between 35 and 59 weight percent. The synergism among the nickel catalytic properties, having low hydrogen over-potential and high hydrogen adsorption of cobalt, is best realized in this conditions and allow obtaining a largest value of exchange current density. ª (A. Dell'Era).

downloadDownload free PDFView PDFchevron_rightHydrogen-absorbing alloys for the NICKEL–METAL hydride batteryD. Northwood

International Journal of Hydrogen Energy, 1998

In recent years\ owing to the rapid development of portable electronic and electrical appliances\ the market for rechargeable batteries has increased at a high rate[ The nickel!metal hydride battery "Ni:MH# is one of the more promising types\ because of its high capacity\ high!rate charge:discharge capability and non!polluting nature[ This type of battery uses a hydrogen storage alloy as its negative electrode[ The characteristics of the Ni:MH battery\ including discharge voltage\ high!rate discharge capability and charge:discharge cycle lifetime are mainly determined by the construction of the negative electrode and the composition of the hydrogen!absorbing alloy[ The negative electrode of the Ni:MH battery described in this paper was made from a mixture of hydrogen!absorbing alloy\ nickel powder and polytetra~uoroethylene "PTFE#[ A multicomponent MmNi 4 !based alloy "Mm 9[84 Ti 9[94 Ni 2[74 Co 9[34 Mn 9[24 Al 9[24 # was used as the hydrogen!absorbing alloy[ The discharge characteristics of the negative electrode\ including discharge capacity\ cycle lifetime\ and polarization overpotential\ were studied by means of electrochemical experiments and analysis[ The decay of the discharge capacity for the Ni:MH battery "AA size\ 0 Ah# was about 0) after 099 charge:discharge cycles and 09) after 499 charge:discharge cycles[ Þ 0887 International Association for Hydrogen Energy

downloadDownload free PDFView PDFchevron_rightA voltammetric study of α- and β-hydroxides over nickel alloysMarcio Andrade

Electrochimica Acta, 2002

The hydrogen evolution reaction (HER) is one of the most studied electrochemical process due to the alternative energy conversion and the importance in some chemical process. The search for new electrocatalytic materials lead to investigate metals and alloys with particular characteristics/properties. This paper describes aspects of hydrogen adsorption and Ni-hydroxide formation over nickel alloys (SAF2205, INCONEL625 and MONEL400) utilizing cyclic voltammetry. The SAF2205 (6.4% Ni) alloy present behavior analogue to pure Ni electrodes to hydroxide species, and can bring some advantages to HER compared with the carbon steel (SAE1020) electrode commonly utilized in industrial process.

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FAQs

AI

What is the effect of pH on nickel hydride formation during hydrogenation?add

The study reveals that nickel transforms into b-nickel hydride at pH values up to 2.0, with phase transformation ceasing at pH 2.1, attributed to hydrogen evolution alkalizing the electrode layer.

How does the presence of H2SeO3 influence pH-dependent hydrogenation?add

H2SeO3 enhances hydrogenation in acidic solutions, but shows a termination of nickel hydride formation beyond pH 2.1, as it requires conditions promoting H2Se formation.

What happens to hydrogen solubility in steel at varying pH levels?add

Hydrogen solubility in steel peaks at a pH of about 2, decreasing significantly above pH 3.0, indicating a correlation with the activity of hydronium ions.

What observations were made regarding the electrochemical reduction of H2SeO3?add

During cathodic polarization, H2SeO3 transforms, resulting in selenium deposition on nickel surfaces, influencing subsequent hydrogenation behavior.

What implications does pH have for nickel coatings during cathodic polarization?add

The study indicates that alterations in potential and internal stresses in nickel coatings during polarization relate to pH, especially with co-deposited additives affecting hydrogenation.

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The conditions of electrochemical formation of nickel hydride are investigated. The electrochemical properties of different nickel-based materials (bulk, porous, foamed tapes) are examined to state the hydrogen adsorption/absorption phenomena and possibility to use them as a negative electrode in hydrogen devices (electrolyzers, rechargeable batteries, fuel cells). Surface activation of nickel materials are made by electroplating and etching methods. Thin palladium coating is used to prove the formation of nickel hydride during cathodic charging. Volt-amperometric and kinetic measurements show that not only palladium, but also activated nickel plays important role in the surface activation of electrode materials and promotion of hydrogen absorption in nickel substrate materials.

downloadDownload free PDFView PDFchevron_rightHydride Effect on the Kinetics of the Hydrogen Evolution Reaction on Nickel Cathodes in Alkaline MediaOmar Teschke

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The time-dependent hydrogen evolution reaction (HER) on Ni electrodes shows a large increase in electrode overpotential with time. This is ascribed to hydride formation at active Ni cathode surfaces. Hydride formation was detected by x-ray diffraction, morphological changes at the electrode surfaces, and resulting changes in secondary electron emissivities. Nickel electrodes annealed for 2 h in an argon atmosphere at 1000~ after HER did not show x-ray lines assigned to hydride. On the other hand, hard nickel electrodes (180 HV5/30) show high overvoltages as well as hydride x-ray diffraction lines after HER. By taking the variation of the nickel electronic density of state following hydrogen sorption into account, we are able to satisfactorily explain the increase in nickel overpotential after a few hours of HER.

downloadDownload free PDFView PDFchevron_rightNi–Sn coatings as cathodes for hydrogen evolution in alkaline solutionsUroš Lačnjevac

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downloadDownload free PDFView PDFchevron_rightElectrodeposition and characterization of Ni–Sn alloy coatings as cathode material for hydrogen evolution reaction in alkaline solutionsUroš Lačnjevac

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Ni-Sn alloy coatings were deposited from the constant composition pyrophosphate-glycine bath at different current densities. Their morphology, composition and phase composition were investigated by SEM, EDS and XRD techniques. It was shown that the morphology of coatings depends on current density, being rougher and more porous with the increase of deposition current density. EDS analysis of the cross sections revealed that the coating composition varies from the substrate surface towards the coating surface, being richer in Ni close to the substrate surface, while the composition on top of the surface was approximately the same for all samples . XRD analysis showed the presence of only one phase in all deposits, NiSn 2 . The increase of Ni-Sn coatings catalytic activity for hydrogen evolution with the increase of deposition current density was shown to be the consequence of their porosity, while the sample with the smooth surface showed lower overvoltage for hydrogen evolution than the commercial De Nora's electrode (DN), indicating synergetic effect of Ni-Sn alloys.

downloadDownload free PDFView PDFchevron_rightCorrosion behaviour of the nickel based materials in an alkaline solution for hydrogen evolutionMihajlo Firak

Indian Journal of Chemical Technology, 2017

Experimental investigations on the nickel based materials in the form of foam and solid plate have been performed. Their application as the electrodes material in an alkaline electrolyzer has been studied. Corrosion potential and Tafels parameters are defined using DC methods, and Ohmic resistance of the electrolyte using AC methods. Active surface area of the foam is defined using BET method. Obtained polarizations curves result in decrease in the resistance to charge-transfer during increasing of electrodes overvoltage. A 1500 times larger active surface of foam insured higher hydrogen evolution at the same overvoltage. As long as it is used high concentrated aqueous media of wt 25% potassium hydroxide solution, corrosion stability of used electrodes material is the first priority.

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Composite Ni-MoO 2 coatings were prepared and characterized with respect to their possible application as electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solution. The composites were electrodeposited onto Ni meshes from an ammonium chloride Ni solution with suspended MoO 2 particles under simulated industrial conditions for the production of commercial cathodes. The influence of the concentration of MoO 2 particles in the solution and deposition current density on the morphology, and chemical and phase composition of the obtained coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Catalytic activity of the coatings for the HER was examined by polarization measurements in a 32 wt. % NaOH solution at 90 °C and compared to the activity of the commercial De Nora's cathode (DN). It was shown that the most active Ni-MoO 2 coating exhibited better polarization characteristics for the HER than the DN cathode. The mechanism of the HER on the specified Ni-MoO 2 coating was investigated in 8 mol dm -3 NaOH at 30 °C by means of steady-state polarization measurements and an electrochemical impedance spectroscopy (EIS). Based on the theoretical interpretation of the experimental data, the rate constants of the three individual steps of the HER were determined and the source of catalytic activity of the coating was elucidated.

downloadDownload free PDFView PDFchevron_rightELECTROCHEMICAL PRODUCTION AND CHARACTERIZATION OF Ni-BASED COMPOSITE COATINGS CONTAINING Mo PARTICLESAntoni Budniok

Rev. Adv. Mater. Sci, 2007

Composite Ni+Mo coatings were obtained by electrodeposition of Ni with Mo particles on a steel substrate from the nickel bath in which metallic powder was suspended by stirring. The deposition was conducted under galvanostatic conditions. Deposits were characterized by the presence of Mo microsize particles embedded into the nanocrystalline nickel matrix. The influence of the metal powder amount in the bath, as well as the deposition current density on the chemical composition of the coatings was investigated. The content of incorporated Mo increases with the increase in the amount of metal powder in the bath, and diminishes with the increase in the deposition current density. The mechanism of metallic particles embedding is explained on the base of Ni 2+ ions adsorption process. Incorporation of Mo particles into electrolytic nickel matrix causes an increase in the real surface area of deposits. Thermal treatment of deposited coatings leads to chemical reactions in the solid state and in a consequence exerts significant influence on their phase composition and surface morphology. As a result of the interaction between the nickel matrix and incorporated Mo particles Ni 3 Mo intermetallic phase and Ni-Mo solid solution are arising. The obtained composite coatings were tested as electrode materials for hydrogen evolution in alkaline environment. Electrochemical characterization of the composites was carried out by steadystate polarization method. It was ascertained, that as-deposited Ni+Mo coatings are characterized by enhanced electrochemical activity for this process, which was confirmed by considerable decrease in the hydrogen evolution overpotential, by a nearly 170-260 mV compared to nickel electrode. Thermal treatment decreases the electrochemical activity of the investigated materials, as the values of hydrogen evolution overpotential on heated coatings are much higher.

downloadDownload free PDFView PDFchevron_rightNi–MoO2 composite cathodes for hydrogen evolution in alkaline solution. Effect of aging of the electrolyte for their electrodepositionUroš Lačnjevac

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In this work, the effect of aging of the electrolyte in the electrodeposition of Ni-MoO 2 composite coatings on their morphology (scanning electron microscopy), chemical composition (energy-dispersive X-ray spectroscopy), polarization characteristics and "service life", tested 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-MoO 2 composite coatings obtained after different aging periods of the electrolyte for deposition (suspension of MoO 2 powder particles in a solution containing 2 M NH 4 Cl + + 0.2 M NiCl 2 ) were compared with that recorded for the commercial De Nora's Ni+RuO 2 cathode coating (DN). It was shown that aging of the electrolyte did not influence the morphology and chemical composition of Ni-MoO 2 composite coatings electrodeposited under conditions simulating their industrial production, while the polarization characteristics for the HER were influenced. The best coating, obtained after 180 days of electrolyte aging, showed a completely different (layered) structure of the deposit and significantly better performance than the commercial DN electrode during the "service life" test.

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downloadDownload free PDFView PDFchevron_rightHydrogen discharge on electrodeposited Ni–Mn–Fe coatings in 30 wo kohStephen Arumainathan

International Journal of Hydrogen Energy, 1999

The hydrogen evolution reaction "HER# has been investigated on NiÐMnÐFe electrocoated cathodes in 29 w:o KOH at 29>C[ NiÐMnÐFe alloys were electrodeposited on mild steel as thin coatings from sulphate baths with ammonium sulphate as additive[ The e}ects of bath composition and deposition current density have been studied[ The cathodes were pre!electrolysed at a cathodic current density i c of 499 mAcm −1 for 29 min before the kinetic parameters of the HER were determined[ NiÐMnÐFe coatings plated from Ni!rich electrolytes and at very high current densities showed improved activity towards the HER in 29 w:o KOH due to signi_cant increase in the exchange current density[ Microstructure examinations indicated that the superior electrocatalytic activity\ seen in coatings obtained at high deposition current densities\ is due to the presence of multi!textures[ The coatings\ in which formation of nanocrystalline grains and development of voids at grain interfaces occurs\ exhibit the maximum electrocatalytic activity towards the HER[ Þ 0888 International Association for Hydrogen Energy[ Published by Elsevier Science Ltd[ All rights reserved[ Corresponding author[ Tel[] ¦80!33!124 1957^¦80!33!124 1345^e!mail] bnlÝmd2[vsnl[net[in

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