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Investigation of the oxygen evolving electrode in pH-neutral electrolytes:Modelling and experiments of the RDE-cell

Electrochimica Acta
Publication Date
DOI: 10.1016/j.electacta.2006.12.048
  • Oxygen Evolution
  • Ph Buffer
  • Rotating Disk Electrode
  • Mathematical Modelling
  • Chromate


Abstract A model has been developed to illustrate the complex interplay between the acidifying electrode reactions for oxygen evolution, mass transport and homogeneous reactions in pH-neutral electrolytes. Modelled polarisation curves of the oxygen evolution reaction were verified by polarisation curves experimentally measured in 5 M NaClO 4 on a RDE of DSA material. The conditions in the simulations and in the experiments were similar to those in the chlorate process (high ionic strength, 70 °C, chromate-containing electrolyte, DSA electrode), in which the oxygen evolution reaction is one of the possible side reactions. The model predicted the concentration gradients of H +, OH −, CrO 4 2− and HCrO 4 − during oxygen evolution on the RDE. It was found that an important part of the chromate buffering effect at high current densities occurs in a thin (in the order of nanometers) reaction layer at the anode. From comparisons between the model and experiments, a buffering reaction has been proposed. The most likely reaction for the chromate buffering in the investigated system is CrO 4 2− reacting with water to HCrO 4 − and OH −. In the chlorate process, where chromate is a buffer and oxygen evolution is a side reaction, it is likely that chromate promotes oxygen evolution from OH −.

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