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

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

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

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

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

Morfologija prahova Ni-Mo-O legura istaloženih elektrohemijskim postupkom iz rastvora amonijum sulfata

The electro deposition of the Ni-Mo-O alloy powders from ammonium sulfate containing electrolytes of different Ni/Mo ions concentration ratios was investigated by the polarization measurements. In all electrolytes similar polarization curves were obtained, characterized by two inflection points Point A, the beginning of the electro deposition process and point B, a moment when the powder electro deposition is controlled by the hydrogen bubbles formation. The morphology of the electrodeposited Ni-Mo-O alloy powders was investigated using SEM. At Ni/Mo ratios higher or equal to 1/1 two types of particles were detected in the powder deposits: spongy-type particles (100 - 200 μm) with flat nodular surface and presence of cavities and agglomerates of similar dimensions characterized by the presence of cracks and cavities, with the nodular surface that is not flat, but is covered by the freshly formed dendrites. At Ni/Mo ratios of 1/3 the contribution of the amorphous-compact deposit is significant, while on top of this deposit rounded dendrite and compact outgrowths were detected.Elektrohemijsko taloženje prahova Ni-Mo-O legura ispitivano je snimanjem polarizacionih dijagrama u sulfatno-amonijačnim elektrolitima pri različitim odnosima Ni/Mo. Sve polarizacione krive okarakterisane su prisustvom dve prelomne tačke (A i B) na dijagramu. Tačka A odgovara početku taloženja Ni-Mo-O legure, dok tačka B reflektuje momenat kada je ukupna elektrohemijska reakcija kontrolisana brzinom formiranja mehurova gasovitog vodonika pri čemu se sa povećanjem koncentracije MoO4 2- jona u elektrolitu potencijal početka taloženja (tačka A) pomera ka negativnijim vrednostima. Morfologija čestica prahova ispitivana je skenirajućom elektronskom mikroskopijom (SEM). Prahovi istaloženi na staklastom ugljeniku iz elektrolita sa Ni/Mo ≥ 1/1 okarakterisani su prisustvom dve vrste čestica: sunđeraste čestice veličine 100 - 200 μm relativno glatkih površina sa jasno izraženim rupama i aglomerati sličnih veličina na kojima su prisutne jasno izražene naprsline i rupe, čija površina nije glatka i pokriveni su novo stvorenim grozdovima dendritičnog taloga. Za čestice praha istaloženog iz elektrolita koji sadrži odnos jona Ni/Mo = 1/3 karakteristično je da je udeo kompaktnog taloga značajan u poređenju sa ostalim prahovima, na kome se mogu registrovati dva tipa loptastih izraslina: manje kompaktne izrasline sa jasno definisanim dendritima i znatno kompaktnije izrasline. Kod prahova istaloženih na elektrodi od Ni, pored vrsta čestica koje su registrovane pri taloženju prahova na elektrodi od staklastog ugljenika, može se videti da se deo kompaktnog taloga praktično sastoji iz slojevitih struktura koje su posledica favorizovanog epitaksijalnog rasta taloga na srodnim podlogama

Morfologija prahova Ni-Mo-O legura istaloženih elektrohemijskim postupkom iz rastvora amonijum sulfata

The electro deposition of the Ni-Mo-O alloy powders from ammonium sulfate containing electrolytes of different Ni/Mo ions concentration ratios was investigated by the polarization measurements. In all electrolytes similar polarization curves were obtained, characterized by two inflection points Point A, the beginning of the electro deposition process and point B, a moment when the powder electro deposition is controlled by the hydrogen bubbles formation. The morphology of the electrodeposited Ni-Mo-O alloy powders was investigated using SEM. At Ni/Mo ratios higher or equal to 1/1 two types of particles were detected in the powder deposits: spongy-type particles (100 - 200 μm) with flat nodular surface and presence of cavities and agglomerates of similar dimensions characterized by the presence of cracks and cavities, with the nodular surface that is not flat, but is covered by the freshly formed dendrites. At Ni/Mo ratios of 1/3 the contribution of the amorphous-compact deposit is significant, while on top of this deposit rounded dendrite and compact outgrowths were detected.Elektrohemijsko taloženje prahova Ni-Mo-O legura ispitivano je snimanjem polarizacionih dijagrama u sulfatno-amonijačnim elektrolitima pri različitim odnosima Ni/Mo. Sve polarizacione krive okarakterisane su prisustvom dve prelomne tačke (A i B) na dijagramu. Tačka A odgovara početku taloženja Ni-Mo-O legure, dok tačka B reflektuje momenat kada je ukupna elektrohemijska reakcija kontrolisana brzinom formiranja mehurova gasovitog vodonika pri čemu se sa povećanjem koncentracije MoO4 2- jona u elektrolitu potencijal početka taloženja (tačka A) pomera ka negativnijim vrednostima. Morfologija čestica prahova ispitivana je skenirajućom elektronskom mikroskopijom (SEM). Prahovi istaloženi na staklastom ugljeniku iz elektrolita sa Ni/Mo ≥ 1/1 okarakterisani su prisustvom dve vrste čestica: sunđeraste čestice veličine 100 - 200 μm relativno glatkih površina sa jasno izraženim rupama i aglomerati sličnih veličina na kojima su prisutne jasno izražene naprsline i rupe, čija površina nije glatka i pokriveni su novo stvorenim grozdovima dendritičnog taloga. Za čestice praha istaloženog iz elektrolita koji sadrži odnos jona Ni/Mo = 1/3 karakteristično je da je udeo kompaktnog taloga značajan u poređenju sa ostalim prahovima, na kome se mogu registrovati dva tipa loptastih izraslina: manje kompaktne izrasline sa jasno definisanim dendritima i znatno kompaktnije izrasline. Kod prahova istaloženih na elektrodi od Ni, pored vrsta čestica koje su registrovane pri taloženju prahova na elektrodi od staklastog ugljenika, može se videti da se deo kompaktnog taloga praktično sastoji iz slojevitih struktura koje su posledica favorizovanog epitaksijalnog rasta taloga na srodnim podlogama

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

Morfologija prahova Fe-Ni legura elektrohemijski istaloženih iz citratno-sulfatnih rastvora

The electrochemical deposition of the Fe-Ni alloy powders from citrate-sulfate containing electrolytes of different Ni/Fe ions concentration ratios at pH 4.5 was examined by the polarization measurements. All polarization curves have a similar shape and are characterized by the presence of two inflection points. The first inflection point reflects the beginning of alloy deposition, while the second one (˜) corresponds to the moment when the cathode reaction becomes determined by the rate of hydrogen bubbles formation. The potentials of Fe-Ni alloys deposition at all investigated Ni/Fe ratios are more positive than those for pure metal powders deposition. As the Ni/Fe ratio decreases, the polarization curves are placed at slightly more positive potentials. The morphology of electrodeposited powder particles was investigated using scanning electron microscopy (SEM). A common characteristic of all Fe-Ni alloy powders is the presence of cone shaped cavities. Powder particles electrodeposited at the ratio Ni/Fe = 9/1 are mainly consisted of nodules of either very flat surface or rough surface, with well defined crystals detected only on a few particles. With the decrease of the Ni/Fe ratio, the presence of well defined crystals on the nodule surface becomes more pronounced. In the powder with the highest amount of Fe (Ni/Fe = 1/3), the whole surface of all particles is covered with crystals of different shapes.Elektrohemijsko taloženje prahova Fe-Ni legura ispitivano je snimanjem polarizacionih dijagrama u citratno-sulfatnim rastvorima pri različitom odnosu koncentracija Ni/Fe jona na pH 4,5. Sve polarizacione krive imaju sličan oblik i okarakterisane su prisustvom dve prevojne tačke na dijagramu. Prva prevojna tačka odgovara početku taloženja Fe-Ni legure, dok druga predstavlja momenat kada ukupna elektrohemijska reakcija postaje kontrolisana brzinom formiranja mehurova vodonika. Potencijali taloženja Fe-Ni legura pri svim ispitivanim odnosima Ni/Fe pozitivniji su od potencijala taloženja čistih metala, pri čemu se sa smanjenjem odnosa Ni/Fe polarizacione krive pomeraju ka malo pozitivnijim vrednostima potencijala. Morfologija čestica prahova ispitivana je korišćenjem skenirajuće elektronske mikroskopije (SEM). Zajednička karakteristika svih prahova Fe-Ni legura je prisustvo šupljina konusnog oblika. Čestice praha istaloženog pri odnosu Ni/Fe = 9/1 uglavnom su sastavljene od čvorića, glatke ili neravne površine, kod kojih se na pojedinim mestima mogu uočiti dobro definisani kristali. Sa smanjenjem odnosa Ni/Fe, prisustvo kristala na površini čvorića postaje sve izraženije, dok su kod praha sa najvećim sadržajem Fe (Ni/Fe = 1/3) na celoj površini čestica prisutni kristali različitog oblika

Morfologija prahova Fe-Ni legura elektrohemijski istaloženih iz citratno-sulfatnih rastvora

The electrochemical deposition of the Fe-Ni alloy powders from citrate-sulfate containing electrolytes of different Ni/Fe ions concentration ratios at pH 4.5 was examined by the polarization measurements. All polarization curves have a similar shape and are characterized by the presence of two inflection points. The first inflection point reflects the beginning of alloy deposition, while the second one (˜) corresponds to the moment when the cathode reaction becomes determined by the rate of hydrogen bubbles formation. The potentials of Fe-Ni alloys deposition at all investigated Ni/Fe ratios are more positive than those for pure metal powders deposition. As the Ni/Fe ratio decreases, the polarization curves are placed at slightly more positive potentials. The morphology of electrodeposited powder particles was investigated using scanning electron microscopy (SEM). A common characteristic of all Fe-Ni alloy powders is the presence of cone shaped cavities. Powder particles electrodeposited at the ratio Ni/Fe = 9/1 are mainly consisted of nodules of either very flat surface or rough surface, with well defined crystals detected only on a few particles. With the decrease of the Ni/Fe ratio, the presence of well defined crystals on the nodule surface becomes more pronounced. In the powder with the highest amount of Fe (Ni/Fe = 1/3), the whole surface of all particles is covered with crystals of different shapes.Elektrohemijsko taloženje prahova Fe-Ni legura ispitivano je snimanjem polarizacionih dijagrama u citratno-sulfatnim rastvorima pri različitom odnosu koncentracija Ni/Fe jona na pH 4,5. Sve polarizacione krive imaju sličan oblik i okarakterisane su prisustvom dve prevojne tačke na dijagramu. Prva prevojna tačka odgovara početku taloženja Fe-Ni legure, dok druga predstavlja momenat kada ukupna elektrohemijska reakcija postaje kontrolisana brzinom formiranja mehurova vodonika. Potencijali taloženja Fe-Ni legura pri svim ispitivanim odnosima Ni/Fe pozitivniji su od potencijala taloženja čistih metala, pri čemu se sa smanjenjem odnosa Ni/Fe polarizacione krive pomeraju ka malo pozitivnijim vrednostima potencijala. Morfologija čestica prahova ispitivana je korišćenjem skenirajuće elektronske mikroskopije (SEM). Zajednička karakteristika svih prahova Fe-Ni legura je prisustvo šupljina konusnog oblika. Čestice praha istaloženog pri odnosu Ni/Fe = 9/1 uglavnom su sastavljene od čvorića, glatke ili neravne površine, kod kojih se na pojedinim mestima mogu uočiti dobro definisani kristali. Sa smanjenjem odnosa Ni/Fe, prisustvo kristala na površini čvorića postaje sve izraženije, dok su kod praha sa najvećim sadržajem Fe (Ni/Fe = 1/3) na celoj površini čestica prisutni kristali različitog oblika