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Electrochemical Discharge of Nickel With Low Internal Stresses
(Oles Honchar Dnipro National University, Dnipro, 2025) Sknar, Yuri; Sknar, Irina V.; Butyrina, Tetiana E.
ENG: The work is devoted to the current topic of electrochemical separation of nickel with low voltages from sulfate electrolytes of electroextraction. Scrap processing of strategic nickel-containing superalloys with electroextraction of nickel is an urgent task today. Electrochemically deposited nickel is characterized by high internal tensile stresses, which leads to its delamination from the cathode surface. To reduce the internal stresses of nickel deposits obtained in such systems, it is proposed to use sulfur-containing organic compounds of sodium allylsulfonate, sodium orthoarylsulfonate, and sodium propynylsulfonate. It was established that allylsulfonate and orthoarylsulfonate practically do not affect the kinetics of nickel release. Propynyl sulfonate with a concentration of more than 5 mmol/l significantly inhibits the process of electrodeposition of nickel, which is related to the adsorption capacity of this compound with the triple bond present in the molecule. It is shown that due to the presence of a sulfo group in the composition of the molecules, the used organic additives contribute to the reduction of the internal stresses of nickel deposits. It was established that allyl sulfonate and orthoaryl sulfonate are the most promising reagents that contribute to reducing the internal stresses of electrodeposited nickel. Lowstress nickel deposits can be obtained in the range of current densities from 2 to 7 A/dm2 at a concentration of these additives from 15 to 30 mmol/l.
Electrosynthesis of Ni-Fe Films With Enhanced Electrocatalytic Activity for Hydrogen Evolution From Alkaline Electrolyte
(Oles Honchar Dnipro National University, Dnipro, 2025) Sukhii, Mykhailo K.; Sknar, Iryna V.; Butyrina, Tetyana E.; Sknar, Yuri E.; Nefedov, Volodymyr G.; Polishchuk, Yuliya V.
ENG: The work is devoted to the topical issue of creating electrocatalysts for hydrogen evolution from alkaline electrolyte. The rapid development of hydrogen energy using the electrolytic method of hydrogen requires the use of cheap, resource-intensive and highly catalytic cathode materials. The most variable and flexible in control is the electrochemical method of synthesizing electrocatalysts of this type. A very promising material for cathodic hydrogen release is the Ni-Fe alloy. The limiting factor for its use is the high internal stresses that arise during its electrosynthesis. To reduce the internal stresses of Ni-Fe electrocatalyst films, sulfur-containing modifiers sodium allyl sulfonate and sodium saccharinate were used in this work, which were introduced into the methanesulfonate electrolyte of electrodeposition. It was established that increasing the concentration of sodium allyl sulfonate from 30 to 100 mmol/l leads to a decrease in internal stresses from 300 MPa to 100 MPa. The use of sodium saccharinate in a concentration of 0.5 mmol/l to 6 mmol/l contributes to a decrease in internal stresses from 300 MPa to 0 MPa. This effect of modifiers on internal stresses is associated with a change in the alloy structure due to the incorporation of sulfur and hydrocarbon residues of modifiers. It was found that the Ni-Fe alloy obtained in the presence of allyl sulfonate demonstrates high electroactivity, approaching the electroactivity of platinum. This effect is explained by an increase in defects in the crystal lattice and the presence of nickel and iron sulfide particles in the structure of the cathode material. It is recommended to carry out the electrosynthesis of Ni-Fe, as electrocatalysts for hydrogen evolution, from a methanesulfonate electrolyte containing 80–100 mmol/l of sodium allyl sulfonate in the range of current densities from 3 to 7 A/dm2.