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Tungsten based support was prepared by polycondensation of resorcinol and formaldehyde from ammonium metatungstate, in the presence cetyltrimethylammonium bromide (CTABr) surfactant. Pd nanocatalyst on this support was synthesized by borohydride reduction method. The obtained materials were characterized by High Resolution Transmission Electron Microscopy (HRTEM), Electron Energy Loss Spectroscopy (EELS), X-ray Photoelectron Spectroscopy (XPS) and electrochemical measurements. TEM analysis revealed Pd nanoparticles size in the range of a few nanometers, even the clusters of single Pd atoms. X-Ray Photoelectron Spectroscopy was applied to determine surface composition of the substrates. It was found that tungsten based support consisted of W, WC and WO3 species. The presence of metallic palladium - Pd(0) in the Pd/W"WCWO3 catalyst was revealed, as well. The catalytic activity and stability for the oxygen reduction were investigated in acid and alkaline solutions, by cyclic voltammetry and linear sweep voltammetry at the rotating disc electrode. The catalysts' activities were compared to the carbon supported Pd nanoparticles (Vulcan XC 72). WC supported Pd nanoparticles have shown high activity and superior stability, comparable even to Pt based catalysts, especially in alkaline electrolytes.

The oxygen evolution reaction (OER) was studied at pure Ni and Ni-(Ebonex/Ir) composite coatings in 1 M NaOH solution at 25 °C. Ni-(Ebonex-supported Ir) coatings were electrodeposited from a nickel Watts bath containing different concentrations of suspended Ebonex/Ir particles (0–2 g dm−3) onto a Ni 40 mesh substrate. The surface morphology of the coatings was examined by scanning electron microscopy (SEM), the surface composition by energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRPD) and X-ray photoelectron spectroscopy (XPS), whereas the electrochemical properties were studied by electrochemical impedance spectroscopy (EIS), polarization measurements and cyclic voltammetry (CV). It was shown that the roughness factor of Ni-(Ebonex/Ir) composite coatings calculated relative to the surface area of the pure Ni sample increased with the increasing content of Ebonex/Ir particles in the bath to a maximum value of 40.6. All samples displayed a Tafel slope of about 60 mV dec−1 in the potential range corresponding to lower current densities for the OER. The increase of the apparent activity for the OER at Ni-(Ebonex/Ir) coatings compared with the pure Ni coating was attributed only to the increase of the electrochemically active surface area. Although the pure Ni coating initially exhibited higher intrinsic catalytic activity for the OER than the composite coatings, it also showed a drastic loss of activity after subjecting to continuous oxygen evolution at j = 50 mA cm−2 for 24 h (ΔE = 395 mV). At the same time, the OER overpotential at Ni-(Ebonex/Ir) coatings only negligibly increased after the stability test (ΔE = 22 mV). The improved retention of catalytic activity observed with Ni-(Ebonex/Ir) coatings was ascribed to the presence of IrO2, which inhibited the formation of the inactive γ-NiOOH phase.

Pd-Ni/C catalyst was synthesized employing a borohydride reduction method. The high area Ni was first dispersed on the carbon support and then modified by Pd nanoparticles. Transmission electron microscopy confirmed relatively even distribution of Ni across the carbon support with discrete palladium particles of about 3.3 nm mean diameter on it. Cyclic voltammetry confirmed the presence of Ni on the catalyst surface. The activity of the Pd-Ni/C catalysts for ethanol oxidation reaction (EOR) in alkaline solution was tested under the potentiodynamic and potentiostatic conditions and the results were compared to those obtained on the Pd/C catalyst. It was found that Pd-Ni/C is more active for the EOR compared to Pd/C by a factor up to 3, depending on the type of experiments and whether specific activity or mass activity are considered. During the potentiodynamic stability test an interesting phenomenon of activation of Pd-Ni/C catalyst was observed. It was found that maximum activity is attained after fifty cycles with the positive potential limit of 1.2 V, regardless of whether they were performed in the electrolyte with or without ethanol. It was postulated that potential cycling of the Pd-Ni surface causes reorganization of the catalyst surface bringing Pd and Ni sites to a more suitable arrangement for the efficient ethanol oxidation.

In this work, the hydrogen evolution reaction (HER) was studied on Ru coated Ti2AlC electrodes in 1.0 mol dm(-3) H2SO4 at 25 degrees C. Ti2AlC was found to be a highly stable substrate in sulfuric acid solutions due to the formation of a passivating oxide layer on the surface, which was confirmed by the X-ray photoelectron spectroscopy (XPS) analysis of as-prepared and anodically treated Ti2AlC samples. Ru films were electrodeposited onto Ti2AlC substrates by cycling the potential of Ti2AlC in the solution containing 0.01 mol dm(-3) RuCl3 + 0.1 mol dm(-3) H2SO4 between -0.5 V and 0.4 V vs. a saturated calomel electrode (SCE) at the sweep rate of 20 mV s(-1). Four Ru/Ti2AlC samples were prepared, obtained at 5, 10, 15 and 20 cycles of Ru electrodeposition. Characterization of samples was performed by scanning electron microscopy (SEM) and cyclic voltammetry (CV), while the thickness of the electrodeposited Ru layers was determined by atomic force microscopy (AFM). It was found that the most compact sample with the thickness of about 0.42 mu m was obtained after 5 cycles. Electrochemical impedance spectroscopy (EIS) and steady-state polarization measurements showed that all Ru/Ti2AlC electrodes were exceptionally active for the HER. A Tafel slope of about -60 mV dec(-1) was observed on all polarization curves in the range of high cathodic current densities. Based on formal kinetics analysis, an appropriate mechanism for the HER on Ru/Ti2AlC was suggested.

In this work, the hydrogen evolution reaction (HER) was studied on Ru coated Ti2AlC electrodes in 1.0 mol dm(-3) H2SO4 at 25 degrees C. Ti2AlC was found to be a highly stable substrate in sulfuric acid solutions due to the formation of a passivating oxide layer on the surface, which was confirmed by the X-ray photoelectron spectroscopy (XPS) analysis of as-prepared and anodically treated Ti2AlC samples. Ru films were electrodeposited onto Ti2AlC substrates by cycling the potential of Ti2AlC in the solution containing 0.01 mol dm(-3) RuCl3 + 0.1 mol dm(-3) H2SO4 between -0.5 V and 0.4 V vs. a saturated calomel electrode (SCE) at the sweep rate of 20 mV s(-1). Four Ru/Ti2AlC samples were prepared, obtained at 5, 10, 15 and 20 cycles of Ru electrodeposition. Characterization of samples was performed by scanning electron microscopy (SEM) and cyclic voltammetry (CV), while the thickness of the electrodeposited Ru layers was determined by atomic force microscopy (AFM). It was found that the most compact sample with the thickness of about 0.42 mu m was obtained after 5 cycles. Electrochemical impedance spectroscopy (EIS) and steady-state polarization measurements showed that all Ru/Ti2AlC electrodes were exceptionally active for the HER. A Tafel slope of about -60 mV dec(-1) was observed on all polarization curves in the range of high cathodic current densities. Based on formal kinetics analysis, an appropriate mechanism for the HER on Ru/Ti2AlC was suggested.

The oxygen evolution reaction (OER) was studied at pure Ni and Ni-(Ebonex/Ir) composite coatings in 1 M NaOH solution at 25 degrees C. Ni-(Ebonex-supported Ir) coatings were electro-deposited from a nickel Watts bath containing different concentrations of suspended Ebonex/Ir particles (0-2 g dm(-3)) onto a Ni 40 mesh substrate. The surface morphology of the coatings was examined by scanning electron microscopy (SEM), the surface composition by energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRPD) and Xray photoelectron spectroscopy (XPS), whereas the electrochemical properties were studied by electrochemical impedance spectroscopy (EIS), polarization measurements and cyclic voltammetry (CV). It was shown that the roughness factor of Ni-(Ebonex/Ir) composite coatings calculated relative to the surface area of the pure Ni sample increased with the increasing content of Ebonex/Ir particles in the bath to a maximum value of 40.6. All samples displayed a Tafel slope of about 60 mV dec(-1) in the potential range corresponding to lower current densities for the OER. The increase of the apparent activity for the OER at Ni-(Ebonex/Ir) coatings compared with the pure Ni coating was attributed only to the increase of the electrochemically active surface area. Although the pure Ni coating initially exhibited higher intrinsic catalytic activity for the OER than the composite coatings, it also showed a drastic loss of activity after subjecting to continuous oxygen evolution at j = 50 mA cm(-2) for 24 h (Delta E = 395 mV). At the same time, the OER overpotential at Ni-(Ebonex/Ir) coatings only negligibly increased after the stability test (Delta E = 22 mV). The improved retention of catalytic activity observed with Ni-(Ebonex/Ir) coatings was ascribed to the presence of IrO2 which inhibited the formation of the inactive gamma-NiOOH phase.

In this work, the hydrogen evolution reaction (HER) was studied on Ru coated Ti2AlC electrodes in 1.0 mol dm(-3) H2SO4 at 25 degrees C. Ti2AlC was found to be a highly stable substrate in sulfuric acid solutions due to the formation of a passivating oxide layer on the surface, which was confirmed by the X-ray photoelectron spectroscopy (XPS) analysis of as-prepared and anodically treated Ti2AlC samples. Ru films were electrodeposited onto Ti2AlC substrates by cycling the potential of Ti2AlC in the solution containing 0.01 mol dm(-3) RuCl3 + 0.1 mol dm(-3) H2SO4 between -0.5 V and 0.4 V vs. a saturated calomel electrode (SCE) at the sweep rate of 20 mV s(-1). Four Ru/Ti2AlC samples were prepared, obtained at 5, 10, 15 and 20 cycles of Ru electrodeposition. Characterization of samples was performed by scanning electron microscopy (SEM) and cyclic voltammetry (CV), while the thickness of the electrodeposited Ru layers was determined by atomic force microscopy (AFM). It was found that the most compact sample with the thickness of about 0.42 mu m was obtained after 5 cycles. Electrochemical impedance spectroscopy (EIS) and steady-state polarization measurements showed that all Ru/Ti2AlC electrodes were exceptionally active for the HER. A Tafel slope of about -60 mV dec(-1) was observed on all polarization curves in the range of high cathodic current densities. Based on formal kinetics analysis, an appropriate mechanism for the HER on Ru/Ti2AlC was suggested.

Pd-Ni/C catalyst was synthesized employing a borohydride reduction method. The high area Ni was first dispersed on the carbon support and then modified by Pd nanoparticles. Transmission electron microscopy confirmed relatively even distribution of Ni across the carbon support with discrete palladium particles of about 3.3 nm mean diameter on it. Cyclic voltammetry confirmed the presence of Ni on the catalyst surface. The activity of the Pd-Ni/C catalysts for ethanol oxidation reaction (EOR) in alkaline solution was tested under the potentiodynamic and potentiostatic conditions and the results were compared to those obtained on the Pd/C catalyst. It was found that Pd-Ni/C is more active for the EOR compared to Pd/C by a factor up to 3, depending on the type of experiments and whether specific activity or mass activity are considered. During the potentiodynamic stability test an interesting phenomenon of activation of Pd-Ni/C catalyst was observed. It was found that maximum activity is attained after fifty cycles with the positive potential limit of 1.2 V, regardless of whether they were performed in the electrolyte with or without ethanol. It was postulated that potential cycling of the Pd-Ni surface causes reorganization of the catalyst surface bringing Pd and Ni sites to a more suitable arrangement for the efficient ethanol oxidation.

Nanocomposite cathodes for the hydrogen evolution reaction (HER) were prepared by deposition of RuOx catalyst particles on self-organized titania nanotube (TiNT) arrays of highly developed surface area, following a procedure that involved the initial cathodic intercalation of H+ into the TiNT walls and the subsequent two-step ion-exchange process. Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) analyses of obtained Ru-TiNT samples revealed that the concentration of RuOx particles in the size range of a few nanometers was the highest at the surface of the TiNT layer and steadily decreased to a minimum value at about 4.5 mu m inside the tubes. The capacitive behavior and electrocatalytic activity for the HER of Ru-TiNT nanocomposites, hydrogenated TiNT samples (H-TiNT) and compact TiO2 were investigated in 1.0 M HClO4 solution at room temperature by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis and steady-state polarization measurements. It was shown that cathodic hydrogenation treatment induced a four orders of magnitude higher concentration of electron donors in TiNT structures providing their quasimetallic behavior in the range of potentials corresponding to the HER. Ru-TiNT cathodes exhibited a more than 250 mV lower overpotential for the HER with respect to bare H-TiNT substrates at the current density of -50 mA cm (2). A decrease of the Tafel slope from about -120 mV/dec for H-TiNT samples to as low as -70 mV/dec for the Ru-TiNT sample with longer tubes was explained by the formal kinetics approach.

Two binary Ru-Ti oxides, Rum Ti0.9O2 and Ru0.7Ti0.3O2, were synthesized by the sol-gel method and used as an electrocatalyst support. The system was characterized by XRD, EDS, TEM and cyclic voltammetry. The Rum Ti0.9O2 and Ru0.7Ti0.3O2 consist of two phases of anatase and rutile structure. An average size of the Pt nanoparticles supported on them is similar to 3.5 nm and they are deposited on both Ru and Ti-rich domains. The supports exhibited good conductivity and electrochemical stability. The onset potentials of COads oxidation on the synthesized catalysts and on commercial PtRu/C are similar to each other and lower than that on Pt/C. This suggests that in Pt/Rum Ti0.9O2 and Pt/Ru0(.7)Ti(0.3)O(2) the Pt nanoparticles are in close contact with Ru atoms from the support, which enables the bifunctional mechanism. The activity and stability of the catalysts for methanol oxidation were examined under potentiodynamic and potentiostatic conditions. While the activity of Pt/Rum Ti0.9O2 is unsatisfactory, the performance of Pt/Ru0.7Ti0.3O2 is comparable to PtRu/C. For example, in the potentiostatic test at 0.5 V the activities after 25 min are 0.035 mA cm(-2) and 0.022 mA cm(-2) for Pt/Ru0.7Ti0.3O2 and PtRu/C, respectively. In potentiodynamic test the activities at 0.5V after 250 cycles are around 0.02 mA cm(-2) for both catalysts.

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.

In order to examine the intrinsic catalytic activity and durability of the electrodeposited NiSn alloy electrodes and the electrodeposited Ni as a reference electrode material for the oxygen evolution reaction (OER) in alkaline solutions, a comparative investigation was performed. A series of NiSn electrodes were prepared by electrodeposition of NiSn alloys at different current densities onto a Ni40 mesh substrate. The surface morphology and chemical composition were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The electrochemical surface characteristics were studied by cyclic voltammetry in order to find interdependence between the nickel oxyhydroxide surface electrochemistry and the activity of the electrode for the OER Quasi steady-state polarization measurements and electrochemical impedance spectroscopy (EIS) were used to determine kinetically significant parameters including the Tafel slopes and exchange current densities. Two well-defined Tafel slopes, the same for all investigated NiSn electrodes, were observed at the polarization curves, indicating that the OER was controlled by the same mechanism. It was demonstrated that any anodic polarization pretreatment led to a shift of the anodic and cathodic current peaks corresponding to the Ni(II)/Ni(III) redox transition towards cathodic potentials and, consequently, to some activation of the NiSn electrodes. The opposite behavior was obtained for the Ni electrode. Prolonged anodic polarization led to a loss of the initial catalytic activity of the Ni electrode, which was explained by the increase in the portion of gamma-NiOOH at the Ni electrode surface. Among the investigated NiSn electrodes, the NiSn100 electrode, prepared by electrodeposition at the highest cathodic current density of - 100 mAcm(-2), exhibited the highest apparent catalytic activity for the OER, entirely due to surface roughness effects. Despite the fact that the NiSn electrodes did not exhibi

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 degrees 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.

Two binary Ru-Ti oxides, Rum Ti0.9O2 and Ru0.7Ti0.3O2, were synthesized by the sol-gel method and used as an electrocatalyst support. The system was characterized by XRD, EDS, TEM and cyclic voltammetry. The Rum Ti0.9O2 and Ru0.7Ti0.3O2 consist of two phases of anatase and rutile structure. An average size of the Pt nanoparticles supported on them is similar to 3.5 nm and they are deposited on both Ru and Ti-rich domains. The supports exhibited good conductivity and electrochemical stability. The onset potentials of COads oxidation on the synthesized catalysts and on commercial PtRu/C are similar to each other and lower than that on Pt/C. This suggests that in Pt/Rum Ti0.9O2 and Pt/Ru0(.7)Ti(0.3)O(2) the Pt nanoparticles are in close contact with Ru atoms from the support, which enables the bifunctional mechanism. The activity and stability of the catalysts for methanol oxidation were examined under potentiodynamic and potentiostatic conditions. While the activity of Pt/Rum Ti0.9O2 is unsatisfactory, the performance of Pt/Ru0.7Ti0.3O2 is comparable to PtRu/C. For example, in the potentiostatic test at 0.5 V the activities after 25 min are 0.035 mA cm(-2) and 0.022 mA cm(-2) for Pt/Ru0.7Ti0.3O2 and PtRu/C, respectively. In potentiodynamic test the activities at 0.5V after 250 cycles are around 0.02 mA cm(-2) for both catalysts.

In this work the "service life test" (SLT) of the NiSn alloy coatings as cathodes for the hydrogen evolution reaction (HER), deposited onto Ni 40 mesh at different current densities from the bath containing 0.1 mol dm(-3) SnCl2 + 0.3 mol dm(-3) NiCl2 + 0.6 mol dm(-3) K4P2O7 + 0.3 mol dm(-3) NH2CH2COOH at 50 degrees C, was investigated and compared with that recorded for the commercial Ni-RuO2 De Nora's (DN) cathode. The morphology and chemical compositions of all NiSn samples were investigated by SEM and EDS techniques before and after the SLT. HER during the SLT has also been monitored by EIS technique. The chemical compositions of surfaces of all NiSn alloy samples, as well as EIS results, were found to depend on the number of cycles performed during the SLT. The decrease of their catalytic activity for the HER in 32 wt.% NaOH at 90 degrees C with increasing the number of cycles (about 20-25 mV after 25 cycles) was practically identical to that for DN cathode, while NiSn samples deposited at -30 mA cm(-2), -60 mA cm(-2) and -100 mA cm(-2) possessed lower overpotential for the HER before and after SLT in comparison with that for the DN cathode. It is confirmed by the SEM-EDS and EIS analysis of the NiSn samples that the minor loss of the catalytic activity for the HER is the consequence of the change of chemical composition of NiSn coatings and decrease of the active surface area. This decrease is ascribed to partially eroded NiSn coatings due to oxygen evolution during the SLT.

The Zn-Mn alloy electrodeposition on a steel electrode in chloride electrolyte was investigated with the aim of obtaining deposits with as high as possible Mn percent. It was found that the deposition current density and concentration of Mn2+ ion in the chloride electrolyte significantly affect the Mn content in the alloy coating as well as the coating surface morphology. There was a transition from dendritic and spongy to smooth, bright, and amorphous structure of Zn-Mn deposits, when some critical deposition current density was reached, probably due to the metal oxyhydroxide inclusion in the coatings. Several plating additives were tested in order to decrease the hydroxide content and to improve surface appearance of the deposits. The 4-hydroxy-benzaldehyde was found to decrease oxygen and increase Mn percent in the coatings, and to significantly improve their surface morphology.

Ru-doped SnO2 powder, (RuxSn1-x)O2, with a Sn:Ru atomic ratio of 9:1 was synthesized and used as a support for Pt nanoparticles (30 mass % loading). The (RuxSn1-x)O2 support and the Pt/(RuxSn1-x)O2 catalyst were characterized by X-ray diffraction measurements, energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM). The (RuxSn1-x)O2 was found to be a two-phase material consisting of probably a solid solution of RuO2 in SnO2 and pure RuO2. The average Pt particle size determined by TEM was 5.3 nm. Cyclic voltammetry of Pt/(RuxSn1-x)O2 indicated good conductivity of the support and displayed the usual features of Pt. The results of the electrochemical oxidation of COads and methanol on Pt/(RuxSn1-x)O2 were compared with those on commercial Pt/C and PtRu/C catalysts. Oxidation of COads on Pt/(RuxSn1-x)O2 starts at lower positive potentials than on PtRu/C and Pt/C. Potentiodynamic polarization curves and chronoamperometric curves of methanol oxidation indicated higher initial activity of the Pt/(RuxSn1-x)O2 catalyst compared to PtRu/C, but also a greater loss in current density over time. A potentiodynamic stability test of the catalysts revealed that deactivation of Pt/(RuxSn1-x)O2 and Pt/C was primarily caused by poisoning of the Pt surface by residues of methanol oxidation, which mostly occurred during the first potential cycle. In the case of PtRu/C, the poisoning of the surface was minor and deactivation was caused by surface area loss of the PtRu., Sintetizovan je prah SnO2 dopovan rutenijumom, (RuxSn1-x)O2, sa atomskim odnosom Sn:Ru od 9:1, i korišćen kao nosač nanočestica platine. Udeo Pt u dobijenom katalizatoru, Pt/(RuxSn1-x)O2, bio je 30 mas. %. Nosač i katalizator su karakterisani difrakcijom X-zraka, energetski disperzivnom spektroskopijom X-zraka i transmisionom elektronskom mikroskopijom (TEM). Pokazano je da je (RuxSn1-x)O2 dvofazni materijal koji verovatno sadrži čvrst rastvor RuO2 u SnO2 i čist RuO2. Prosečna veličina zrna Pt, određena TEM analizom, iznosi 5,3 nm. Ciklična voltametrija Pt/(RuxSn1-x)O2 ukazala je na dobru provodnost nosača katalizatora i na uobičajene karakteristike Pt. Upoređeni su rezultati elektrohemijske oksidacije COads na Pt/(RuxSn1-x)O2, Pt/C i PtRu/C. Oksidacija COads na Pt/(RuxSn1-x)O2 počinje na negativnijim potencijalima u odnosu na PtRu/C i Pt/C. Potenciodinamičke polarizacione krive i hronoamperometrijske krive za oksidaciju metanola ukazuju na veću početnu aktivnost katalizatora Pt/(RuxSn1-x)O2 u odnosu na PtRu/C, ali i na veće smanjenje gustine struje tokom vremena. Test potenciodinamičke stabilnosti katalizatora je ukazao da je smanjenje aktivnosti Pt/(RuxSn1-x)O2 i Pt/C prvenstveno prouzrokovano trovanjem površine Pt proizvodima nepotpune oksidacije metanola, koje se uglavnom odigrava tokom prvog ciklusa. Kod PtRu/C trovanje površine je minimalno, a smanjenje aktivnosti je prouzrokovano smanjenjem elektrohemijski aktivne površine PtRu.

Ru-doped SnO2 powder, (RuxSn1-x)O2, with a Sn:Ru atomic ratio of 9:1 was synthesized and used as a support for Pt nanoparticles (30 mass % loading). The (RuxSn1-x)O2 support and the Pt/(RuxSn1-x)O2 catalyst were characterized by X-ray diffraction measurements, energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM). The (RuxSn1-x)O2 was found to be a two-phase material consisting of probably a solid solution of RuO2 in SnO2 and pure RuO2. The average Pt particle size determined by TEM was 5.3 nm. Cyclic voltammetry of Pt/(RuxSn1-x)O2 indicated good conductivity of the support and displayed the usual features of Pt. The results of the electrochemical oxidation of COads and methanol on Pt/(RuxSn1-x)O2 were compared with those on commercial Pt/C and PtRu/C catalysts. Oxidation of COads on Pt/(RuxSn1-x)O2 starts at lower positive potentials than on PtRu/C and Pt/C. Potentiodynamic polarization curves and chronoamperometric curves of methanol oxidation indicated higher initial activity of the Pt/(RuxSn1-x)O2 catalyst compared to PtRu/C, but also a greater loss in current density over time. A potentiodynamic stability test of the catalysts revealed that deactivation of Pt/(RuxSn1-x)O2 and Pt/C was primarily caused by poisoning of the Pt surface by residues of methanol oxidation, which mostly occurred during the first potential cycle. In the case of PtRu/C, the poisoning of the surface was minor and deactivation was caused by surface area loss of the PtRu., Sintetizovan je prah SnO2 dopovan rutenijumom, (RuxSn1-x)O2, sa atomskim odnosom Sn:Ru od 9:1, i korišćen kao nosač nanočestica platine. Udeo Pt u dobijenom katalizatoru, Pt/(RuxSn1-x)O2, bio je 30 mas. %. Nosač i katalizator su karakterisani difrakcijom X-zraka, energetski disperzivnom spektroskopijom X-zraka i transmisionom elektronskom mikroskopijom (TEM). Pokazano je da je (RuxSn1-x)O2 dvofazni materijal koji verovatno sadrži čvrst rastvor RuO2 u SnO2 i čist RuO2. Prosečna veličina zrna Pt, određena TEM analizom, iznosi 5,3 nm. Ciklična voltametrija Pt/(RuxSn1-x)O2 ukazala je na dobru provodnost nosača katalizatora i na uobičajene karakteristike Pt. Upoređeni su rezultati elektrohemijske oksidacije COads na Pt/(RuxSn1-x)O2, Pt/C i PtRu/C. Oksidacija COads na Pt/(RuxSn1-x)O2 počinje na negativnijim potencijalima u odnosu na PtRu/C i Pt/C. Potenciodinamičke polarizacione krive i hronoamperometrijske krive za oksidaciju metanola ukazuju na veću početnu aktivnost katalizatora Pt/(RuxSn1-x)O2 u odnosu na PtRu/C, ali i na veće smanjenje gustine struje tokom vremena. Test potenciodinamičke stabilnosti katalizatora je ukazao da je smanjenje aktivnosti Pt/(RuxSn1-x)O2 i Pt/C prvenstveno prouzrokovano trovanjem površine Pt proizvodima nepotpune oksidacije metanola, koje se uglavnom odigrava tokom prvog ciklusa. Kod PtRu/C trovanje površine je minimalno, a smanjenje aktivnosti je prouzrokovano smanjenjem elektrohemijski aktivne površine PtRu.

The hydrogen evolution reaction (HER) was studied on Ni, Ni-Ebonex and Ni-(Ebonex-Ru) coatings in 1 mol dm(-3) NaOH solution at 25 degrees C. The composite coatings were electro-deposited from a nickel Watts-type bath containing suspended Ebonex (chemical composition mainly Ti4O7) or Ebonex-supported Ru(10 wt.%) particles (0-10 g dm(-3)) onto Ni mesh substrate. The electrodes were investigated by cyclic voltammetry (CV), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), electrochemical impedance spectroscopy (EIS) and polarization measurements. These investigations showed that the roughness factor of the Ni-(Ebonex-Ru) and the Ni-Ebonex coating was 29 and 6 times higher than that of a pure Ni coating, respectively. In the whole potential range of the HER only one Tafel slope of about -120 mV was present at the polarization curves of Ni and Ni-Ebonex electrodes, with increased activity of the latter being attributed only to the increase of the electrochemically active surface area. The Ni(Ebonex-Ru) electrodes exhibited the highest intrinsic catalytic activity with two Tafel slopes, indicating also that the HER takes place exclusively. on Ru active sites.

In this work the hydrogen evolution reaction (HER) at Ni-Sn alloy coatings, deposited onto Ni 40 mesh at different current densities from the bath containing 0.1 mol dm(-3) SnCl2 + 0.3 mol dm(-3) NiCl2 in the pyrophosphate-glycine solutions, was investigated by polarization and EIS measurements. The morphology and chemical compositions of all samples were investigated by the SEM and EDS techniques. It was shown that their morphologies and chemical compositions depend on the deposition current density. The increase of their catalytic activity for the HER in 6 mol dm(-3) KOH and in 1 mol dm(-3) NaOH with increasing the deposition current density was shown to be the consequence of the change of both: their chemical composition and morphology.

In this work, the effect of aging of the electrolyte in the electrodeposition of Ni MoO2 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 degrees 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 a solution containing 2 M NH4Cl + + 0.2 M NiCl2) were compared with that recorded for the commercial De Nora's 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 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.

Composite Ni-MoO2 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 MoO2 particles under simulated industrial conditions for the production of commercial cathodes. The influence of the concentration of MoO2 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 degrees C and compared to the activity of the commercial De Nora's cathode (DN). It was shown that the most active Ni-MoO2 coating exhibited better polarization characteristics for the HER than the DN cathode. The mechanism of the HER on the specified Ni-MoO2 coating was investigated in 8 mol dm(-3) NaOH at 30 degrees 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.

Additives are necessary in the electrodeposition of Zn-Mn alloys at high current densities, in order to reduce the hydrogen evolution reaction and prevent dendrite formation. The influences of two aromatic aldehydes, 4-hydroxy-benzaldehyde and 3,4-dimethoxy-benzaldehyde, as additives in the Zn-Mn plating electrolyte, were examined in this study. The characterization of the coatings by scanning electron microscopy and X-ray energy dispersive spectroscopy, as well as an examination of the effect of the additives by electrochemical methods, indicated a complex involvement of additive molecules in hydrogen evolution, as well as in Zn2+ and Mn2+ reduction. Consequently, a levelling action could be achieved and the chemical composition of the Zn-Mn alloy tailored by the addition of the proper type and concentration of additive in the plating electrolyte.

Ru-doped SnO2 powder, (RuxSn1-x)O-2, with a Sn:Ru atomic ratio of 9:1 was synthesized and used as a support for Pt nanoparticles (30 mass % loading). The (RuxSn1-x)O-2 support and the Pt/(RuxSn1-x)O-2 catalyst were characterized by X-ray diffraction measurements, energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM). The (RuxSn1-x)O-2 was found to be a two-phase material consisting of probably a solid solution of RuO2 in SnO2 and pure RuO2. The average Pt particle size determined by TEM was 5.3 nm. Cyclic voltammetry of Pt/(RuxSn1-x)O-2 indicated good conductivity of the support and displayed the usual features of Pt. The results of the electrochemical oxidation of COad, and methanol on Pt/(RuxSn1-x)O-2 were compared with those on commercial Pt/C and PtRu/C catalysts. Oxidation of COads on Pt/(RuxSn1-x)O-2 starts at lower positive potentials than on PtRu/C and Pt/C. Potentiodynamic polarization curves and chronoamperometric curves of methanol oxidation indicated higher initial activity of the Pt/(RuxSn1-x)O-2 catalyst compared to PtRu/C, but also a greater loss in current density over time. A potentiodynamic stability test of the catalysts revealed that deactivation of Pt/(RuxSn1-x)O-2 and Pt/C was primarily caused by poisoning of the Pt surface by residues of methanol oxidation, which mostly occurred during the first potential cycle. In the case of PtRu/C, the poisoning of the surface was minor and deactivation was caused by surface area loss of the PtRu.

The electrodeposition of Ni-MoO2 composite coatings is a specific process taking place under defined hydrodynamic conditions. In this work the influence of hydrodynamics, current density, and MoO2 concentration on the electrodeposition of Ni-MoO2 coatings from a suspension of MoO2 particles in a Watt’s type bath were investigated by comparison of their polarization characteristics for the hydrogen evolution reaction (HER) in 1 M NaOH at room temperature. It was shown that electrolyte and air flow rates influence the process of coating electrodeposition at low concentrations of MoO2. With increases in MoO2 concentration the current density became the main parameter influencing the coatings’ properties. The best coating, with the lowest over-voltage for the HER, was obtained from the suspension containing 3 g dm-3 of MoO2 particles. The over-voltage of this coating was 57 mV lower for the HER at j = –0.3 A cm-2 (the current density used in industrial applications) than that for the commercial De Nora’s Ni + RuO2 electrode.

The Zn-Mn alloy electrodeposition on a steel electrode in chloride electrolyte was investigated with the aim of obtaining deposits with as high as possible Mn percent. It was found that the deposition current density and concentration of Mn2+ ion in the chloride electrolyte significantly affect the Mn content in the alloy coating as well as the coating surface morphology. There was a transition from dendritic and spongy to smooth, bright, and amorphous structure of Zn-Mn deposits, when some critical deposition current density was reached, probably due to the metal oxyhydroxide inclusion in the coatings. Several plating additives were tested in order to decrease the hydroxide content and to improve surface appearance of the deposits. The 4-hydroxy-benzaldehyde was found to decrease oxygen and increase Mn percent in the coatings, and to significantly improve their surface morphology.

In this study, different Ni-W coatings, obtained by cheap and technologically simple electrodeposition method, were examined as potential electrocatalysts for the hydrogen evolution reaction (HER). All electrodepositions were done on a Ni mesh substrate from ammoniacal-citrate bath containing different concentrations of Na2WO4. The influence of deposition parameters, such as deposition current density, pH and composition of ammoniacal-citrate bath on electrocatalytic activity of obtained Ni-W coatings toward HER was examined by polarization curve measurements in 6 M KOH at room temperature. The morphology and tungsten content of the Ni-W coatings were investigated by means of SEM and EDS analysis. All investigated electrodes have shown high electrocatalytic activity for the HER. The samples obtained at higher deposition current densities had the lowest overvoltage for the HER. It has been shown that the plating bath pH value is very important parameter in obtaining active coatings. Results of the analysis of polarization curves, morphology of deposited Ni-W coatings and the content of tungsten in the coatings, indicate that the surface roughness of the coatings is responsible for their catalytic activity towards HER.

The oxidative behaviour of amlodipine besylate was studied. The gold electrode and Au/o-MWCNT (oxidized multi-wall carbon nanotubes) were used for determination of amlodipine besylate standard and as a content of Alopres tablet, in 0.05 M NaHCO3 and in phosphate buffer (pH=11) by cyclic voltammetry and square-wave anodic stripping voltammetry. Electrode surfaces were characterized by AFM in the presence of amlodipine and the concentrations of drugs in electrolytes were simultaneously followed by HPLC. The linear dependency of the anodic currents of amlodipine besylate as standard and in Alopres tablet vs. concentration was observed in both electrolytes, but in phosphate buffer for the higher concentrations. The peak currents obtained in all experiments are more than fifty-fold higher comparing to all previously published results concerning the glassy carbon electrode and the carbon paste electrode. The gold electrode is better catalyst for anodic oxidation of amlodipine besylate than glassy carbone. The results obtained with Au/o-MWCNT show lower anodic activity comparing to previously published GC/o-MWCNT. GC/o-MWCNT is better catalyst than Au/o-MWCNT under similar experimental conditions.

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.

In this work polarization characteristics and "service life" test of the non-noble metal composite coatings Ni-MoOx and Ni-MoO2 for hydrogen evolution reaction (HER) in 32 wt.% NaOH at 90 degrees C were investigated and compared with that recorded for De Nora's commercial Ni + RuO2 cathode coating (DN). It was shown that under conditions of industrial application in the "zero-gap" membrane cells the lowest over-voltage for HER has been recorded for the Ni-MoO2 coating. At the same time the "service life" test was performed on all three electrodes in the same solution. This test was based on monitoring the current density response before and after repetitive cycling of these electrodes with 50 mV s(-1) in the potential range from hydrogen (-1.25 V vs. SCE) to oxygen (0.50 V vs. SCE) evolution. It was shown that the activity for all electrodes at the end of a "service life" test dropped to approximately 54% of the initial value, being comparable with the results obtained for Pt-based cathodes. The SEM-EDS analysis of the electrodes after the "service life" test showed that the Ni-MoO2 is much more stable than the Ni-MoOx composite coating and could be promising replacement for the commercial cathode.

As a result of research on the non-noble metal-based composite electrocatalysts for the hydrogen evolution reaction (HER), the Ni-MoO2 composite coating was produced by electrodeposition from an NH4Cl and NiCl2 containing solution with suspended MoO2 powder particles, exhibiting almost the identical activity for the HER as the commercial cathode in conditions of industrial application and satisfactory mechanical stability. In this work, investigations were extended to the kinetics and mechanism of the HER on the Ni-MoO2 electrode in 8 M NaOH solution at 30 degrees C. The steady-state polarization curve for the HER was characterized by only one Tafel slope of -122 mV/dec. Kinetic parameters for the HER, as well as a contribution of surface roughness to the catalytic activity, were evaluated using an electrochemical impedance spectroscopy (EIS) technique. On the basis of the presented theoretical model for the faradaic impedance of the HER, the rate constants of the individual steps were determined by simulating both polarization and EIS experimental data. It was found that the reaction equally proceeds via the Volmer-Heyrovsky and Volmer-Tafel routes at lower overpotentials, while at higher overpotentials the Volmer-Heyrovsky pathway dominates the process with the Heyrovsky step being the rate determining step (rds). A comparison of intrinsic activities of the Ni-MoO2 composite and a flat Ni electrode proved that the combination of Ni and MoO2 produced a true catalytic effect for the HER.

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.

In this work the hydrogen evolution reaction (HER) onto Ni-Sn alloy coatings deposited at different current densities from the bath containing 0.1 M Sn2+ and 0.1 M Ni2+ ions in the pyrophosphate-glycine solution, was investigated by polarization curves and electrochemical impedance spectroscopy (EIS) measurements. Their morphology and chemical composition were investigated by scanning electron microscopy equipped with an energy-dispersive X-ray spectroscopy (SEM-EDS), while the phase composition was investigated by X-ray powder diffraction (XRPD). It was shown that their chemical composition, phase composition and morphology depend on the deposition current density. In deposited samples all detected phases, face centered cubic (fcc) Ni, close packed (hcp) hexagonal Ni3Sn, hexagonal Ni(1-i-x)Sn (0 lt x lt 0.5) which adopts NiAs structure type and monoclinic Ni3Sn4 (CoSn structure type), were of low crystallinity. The increase of the Ni-Sn alloy coatings catalytic activity for HER in 6 M KOH with increasing the deposition current density was shown to be the consequence of the change of all three parameters: chemical composition, phase composition and morphology, with the effect of morphology being the most pronounced.

In this work the electrodeposition of Ni, Sn and Ni-Sn alloy from the solution containing pyrophosphate and/or glycine has been investigated by cyclic voltammmetry (CV), potentiostatic pulse and polarization curve measurements on two substrates, Ni and GC. It has been shown that the process of Sn electrodeposition in pure pyrophosphate solution commences at the potential of about -0.90 V on both substrates being characterized by the formation of isolated 3D crystals and their further growth by the reduction of [Sn(Pyr)(2)](6-) complex. On the GC surface Sn 3D crystals remain isolated, following 3D nucleation and growth mechanism which does not fit any of the theoretically predicted models. Ni-Sn alloy deposition in the solution containing both cations (Sn2+, Ni2+) and both anions (pyrophosphate and glycine) occurs by the same growth mechanism as pure Sn deposition by simultaneous reduction of [Sn(Pyr)(2)](6-), [Ni(Pyr)(2)](6-) and/or [Ni(Pyr)(3)](-) complexes at pH 8.0. Depending on the current density/potential of the Ni-Sn alloy coating deposition onto Ni electrode the composition of the flat and compact coatings varies in the range from 66 to 50 atom% Ni, i.e. 34 to 50 atom% Sn.

Electrodeposition of lead from nitrate electrolyte in constant regimes of electrolysis was analyzed and the obtained powder lead deposits were examined by scanning electron microscopy. Polarization curve for lead electrodeposition consisted of two parts separated by an inflection point. The first part of the polarization curve was characterized by a linear dependence of the current density on overpotential. The linear part of the polarization curve corresponded to ohmic-controlled electrodeposition and single lead crystals were formed in this range of overpotentials. A rapid increase in the current density with increasing overpotential was observed after the inflection point (the second part of the polarization curve). Two-dimensional dendrites were the dominant morphological forms obtained at overpotentials and current densities belonging to the second part of the polarization curve, indicating that the rapid increase of the current density with increasing overpotential corresponded to activation controlled electrodeposition at the tips of the formed dendrites. Comparing the morphologies of the obtained lead deposits with those belonging to the same group of metals (metals characterized by a high exchange current density), such as silver, cadmium, and tin, a strong dependence between the nucleation type and the shape of dendrites for the metals belonging to the same group was established.

The investigations on the effect of the electrolysis conditions, including high speed electroplating, on the content, structure, morphology and some properties of electrodeposited In-Co alloys from citrate electrolytes are presented. It was shown that indium and cobalt could be successfully deposited from acid citrate electrolytes and deposition of alloys with indium content between 20 and 80 wt. % is possible. At high cobalt content, heterogeneous multiphase coatings with spatio-temporal structures are obtained. Spatio-temporal structures could be observed also during electrodeposition under intensive hydrodynamic flow and improved mass transport conditions at high current densities. The structures are obtained for the first time from silver- and cyanide-free non-alkaline stable electrolytes of a relatively simple composition.

MoO3 particles were co-deposited with Ni onto smooth or rough Ni supports from modified Watt baths of different compositions. Morphology and composition of the electrodeposits were characterized by means of cyclic voltammetry, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The electrocatalytic activity of the composite catalysts for H-2 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. The composite Ni-MoOx catalysts exhibited high catalytic activity, similar to that of a commercial Ni-RuO2 catalyst. Stability tests showed that the Ni-MoOx co-deposits were stable under constant current conditions and exhibited excellent tolerance to repeated short-circuiting.

The oxidative behaviour of amlodipine besylate was studied. The gold electrode and Au/o-MWCNT (oxidized multi-wall carbon nanotubes) were used for determination of amlodipine besylate standard and as a content of Alopres tablet, in 0.05 M NaHCO3 and in phosphate buffer (pH=11) by cyclic voltammetry and square-wave anodic stripping voltammetry. Electrode surfaces were characterized by AFM in the presence of amlodipine and the concentrations of drugs in electrolytes were simultaneously followed by HPLC. The linear dependency of the anodic currents of amlodipine besylate as standard and in Alopres tablet vs. concentration was observed in both electrolytes, but in phosphate buffer for the higher concentrations. The peak currents obtained in all experiments are more than fifty-fold higher comparing to all previously published results concerning the glassy carbon electrode and the carbon paste electrode. The gold electrode is better catalyst for anodic oxidation of amlodipine besylate than glassy carbone. The results obtained with Au/o-MWCNT show lower anodic activity comparing to previously published GC/o-MWCNT. GC/o-MWCNT is better catalyst than Au/o-MWCNT under similar experimental conditions.

In this work the Ni–MoOx coatings have been prepared and characterized in view of their possible application as electrocatalysts for hydrogen evolution reaction (HER) in alkaline solution. The procedure of deposition of Ni–MoOx coatings from the Watt’s type bath containing MoO3 powder particles onto Ni mesh, under the conditions of simulated industrial deposition conditions for commercial cathodes, has been presented. The morphology of the obtained coatings was investigated by SEM, the composition by EDS and the phase composition by XRD techniques. The polarization characteristics for hydrogen evolution on the obtained Ni–MoOx coatings were investigated in the 32 wt.% NaOH at 90 °C and compared with the one recorded for the commercial De Nora’s coating (DN). It was shown that the best Ni–MoOx coating exhibits almost identical polarization characteristics as the commercial one. By the cross section and XRD analysis of deposited samples it was confirmed that MoO3 powder particles were not occluded by the Ni deposit and that molybdenum species were deposited from the molybdate ions formed by dissolution of MoO3, following the mechanism of induced co-deposition. The reaction mechanism for MoO3 phase deposition has also been proposed.

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.

The morphology, phase and chemical composition of Ni-Co alloy powders electrodeposited from an ammonium sulfate-boric acid containing electrolyte with different ratio of Ni/Co ions were investigated. The ratios of NVCo ions were 1/1, 1/2 and 1/3. The morphology, chemical composition and phase composition of the electrodeposited alloy powders were investigated using AES, SEM, EDS and XRD analysis. Composition of the electrolyte, i.e. the ratio of Ni/Co concentrations was found to influence both, the alloy phase composition and the morphology of Ni-Co alloy powders. At the highest ratio of Ni/Co = 1/1 concentrations typical 2D fern-like dendritic particles were obtained. With a decrease of NVCo ions ratio among 2D fern-like dendrites, 3D dendrites and different agglomerates were obtained. X-ray diffraction studies showed that the alloy powders mainly consisted of the face-centered cubic alpha-nickel phase and hexagonal close-packed alpha-cobalt phase and minor proportions of face-centered cubic alpha-cobalt phase. The occurrence of the latter phase was observed only in the alloy powder with the higher cobalt concentration in electrolyte. The electrodeposition of Ni-Co powders occurred in an anomalous manner.