On the Suppression of Cathodic Hypochlorite Reduction by ElectrolyteAdditions of Molybdate and Chromate Ions
(English)Manuscript (preprint) (Other academic)
The goal of this study was to gain a better understanding of the feasibility of replacing Cr(VI) in the chlorate process by Mo(VI), focusing on the cathode reaction selectivity for hydrogen evolution on steel and titanium in a hypochlorite containing electrolyte.
To evaluate the ability of Cr(VI) and Mo(VI) additions to hinder hypochlorite reduction, potential sweep experiments on rotating disc electrodes and cathodic current efficiency (CE) measurements on stationary electrodes were performed. Formed electrode films were investigated with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Cathodic hypochlorite reduction is hindered by the Mo-containing films formed on the cathode surface after Mo(VI) addition to the electrolyte, but much less efficient compared to Cr(VI) addition. Very low levels of Cr(VI), in the mM range, can efficiently suppress hypochlorite reduction on polished titanium and steel. Phosphate does not negatively influence the CE in the presence of Cr(VI) or Mo(VI) and the Mo-containing cathode films become thinner if the electrolyte during the film build-up also contains phosphate. For a RuO2-TiO2 anode polarized in electrolyte with 40 mM Mo(VI), the anode potential increased and on the electrode surface, increased molybdenum levels were detected. In an earlier study 40 mM Mo(VI) gave increased by-product oxygen.
Engineering and Technology
Research subject SRA - Energy
IdentifiersURN: urn:nbn:se:kth:diva-95367OAI: oai:DiVA.org:kth-95367DiVA: diva2:527960
QS 20122012-05-232012-05-232012-05-30Bibliographically approved