Effect of Vanadium or Molybdenum Co-deposition on the Hydrogen Overpotential of Cobalt Plated Cathode

Abstract

Hydrogen evolution overpotential of the cobalt plated cathode in a 3.0mol/dm³ NaOH solution at 80°C was studied by comparing polarization curves. For a 20A/dm² plating current density with 3.0mol/dm³ urea added to the cobalt citrate plating bath, a low hydrogen overpotential value was obtained. The value was same to that of rhodium electrode. Vanadium or molybdenum co-deposited cobalt plating cathode had lower hydrogen overpotential than above mentioned pure cobalt plated cathode. Suitable plating conditions for low hydrogen overpotential cathodes were above 4×10^-3 mol/dm³(about 0.8g/dm³) vanadium pentoxide or ammonium molybdate addition and above 30A/dm² plating current densities. Value of overpotential at 25A/dm² current density was 0.1V. This is a comparable value with that of platinized platinum cathode.