Role of Complex Formation in Mass Transport during Nickel Electrodeposition from Low-Concentration Formate–Chloride Electrolytes

Nickel electrodeposition from 0.2 M formate–chloride solutions is studied. Depending on electrolyte pH₀, the highest current density of the electrodeposition of compact nickel deposits varies from 3 (pH₀3.5) to 40 A dm^–2(pH₀2.0). With the current efficiency for nickel taken into account, this corresponds to nickel deposition rates of 3 to 25 A dm^–2. One of the reasons for the high permissible current densities is good buffer properties of the electrolyte. Computer calculations show that the considerable acceleration of the nickel electrodeposition is due to mass transport accelerated by the formation of complex NiL]⁺cations. The complex formation also affects the intensity of interaction between nickel and hydrogen ions transported to the cathode. The current by nickel increases due to the participation of formic acid molecules in the hydrogen evolution.