Solar thermal decoupled water electrolysis process III: The anodic electrochemical reaction in a rotating disc electrode cell

Rachel Silcox, Laura K. Engerer, Shahin Nudehi, Paul Smith, Jon Schoer, Peter T. Krenzke, Robert Palumbo, Luke J. Venstrom

Research output: Contribution to journalArticlepeer-review

Abstract

The electrochemical oxidation of Co2+ is studied at 45 °C using a rotating disc electrode to elucidate the impacts of fluid motion and solid Co3+ product formation on the anode reaction rate. The electrolyte is 40% KOH saturated with Co2+ and the anode is nickel. Inducing laminar flow with rotation at speeds up to 2500 RPM is shown to increase the current density from <1 mA cm-2 to 2–5 mA cm-2 at potentials greater than −0.21 Volts vs. Ag/AgCl. At higher current densities anticipated for commercial application, electrode passivation is a relevant concern. However, bulk electrolysis and cyclic voltammetry—with the latter interpreted using a reaction model to account for the fluid motion—demonstrate that the solid Co3+ deposit is not passivating, but electrochemically active. Deposits up to ≈1 mm thick increase the current, with a sixfold increase demonstrated at 2000 RPM.

Original languageEnglish (US)
Article number115885
JournalChemical Engineering Science
Volume227
DOIs
StatePublished - Dec 14 2020

Keywords

  • Cobalt oxide
  • Concentrated solar energy
  • Electrolysis
  • Hydrogen
  • Rotating disc electrode
  • Voltammetry

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