A Model for the Faradaic Efficiency of Base Metal Electrodeposition from Mildly Acidic Baths to Rotating Disk Electrodes

Abstract

Base metal electrodeposition is inevitably accompanied by parasitic hydrogen evolution. This results in a less-than-unity Faradaic efficiency (FE M ) of metal deposition that is known to depend on many factors like the applied current density, the composition (primarily, the metal ion concentration and the pH) of the depositing bath, and the rate of convection. Analysing how FE M values depend on the current density j under well-defined transport conditions (e.g., by the use of rotating disk electrodes) became an integral part of industrial approaches to the screening of bath compositions applied for base metal electroplating. Yet FE M (j) curves are still not very well understood, and most studies content themselves with their mere qualitative analysis, reaching no conclusions as to the mechanisms of the underlying reactions. We attempt to fill this gap by creating a simple model for FE M (j) curves based on first principles. The presented model can very well be fitted to experimental data obtained for the electrodeposition of nickel and of cobalt, and it yields a consistent set of kinetic and transport parameters over a broad range of pH, rotation rates and current densities. The presented model thus paves the way towards a knowledge-driven benchmarking strategy of base metal electroplating baths.

Past and present of electrochemical science in Hungary

“…Soma Vesztergom constructed a mathematical model of hydrogen evolution from a mildly acidic, unbuffered, stirred aqueous solution when the hydrogen gas stems both from H + ions and from water. This model's predictions are in accord with hydrogen evolution experiments carried out with RDE [37], also even if hydrogen evolution proceeds parallel to a metal deposition [38].…”

Hydrogen Bubble Templated Metal Foams as Efficient Catalysts of CO2 Electroreduction

“…When preparing metal foams, one must keep in mind that exchange current densities found in the literature (like those plotted in Figure 2) are concentration dependent quantities and values found in literature are usually (but not always) normalized to a unity concentration of the metal or H + ions in the bulk solution (for metal deposition and HER, respectively). Thus, the overall electrolyte composition will have a strong effect on determining actual hydrogen evolution/metal deposition current ratios [58] . When preparing metal foams from noble metals, e. g ., from silver, [38] gold [40] or palladium salts, [43] a larger metal salt concentration in the bath may be required than, for example, when depositing normal metals such as Sn or Pb, or even intermediate metals like Cu.…”

“…Naturally, at large negative applied overpotentials or currents, even the direct reduction of H 2 O can serve as means of HER. While in this case it is the autoprotolysis reaction of water that has to be taken into account to describe HER current densities, [48] for buffered systems additional (buffer) equilibria must be considered [58] …”

Onsite Graywater Treatment in a Two-Stage Electro-Peroxone Reactor with a Partial Recycle of Treated Effluent

“…Table shows that the Faradaic efficiency, which is proportional to the total moles of H 2 O 2 produced and the inverse of total charge passed, remained unchanged regardless of the electrolyte conductivity. The constant Faradaic efficiency indicates that other factors such as electrocatalytic activity loss and parasitic side reactions , were not present to suppress the H 2 O 2 generation efficiency. Therefore, the electrolyte conductivity, which was reduced during the reuse of treated graywater as an influent to the first-stage reactor, was the primary factor increasing the extended time required to produce the same concentration of H 2 O 2 .…”