Oxidation of Chloride and Hypochlorite at Pt and RuO2 Anodes

Abstract

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Formation of hypochlorite, chlorate and oxygen during NaCl electrolysis from alkaline solutions at an RuO2/TiO2 anode

“…The ratio between the current density and the initial NaC1 concentration determines to a large extent the initial current efficiency for the chlorate formation. Similar results have been observed for a platinum anode [14,15]. The initial rate of this reaction is, however, much lower for a DSA | electrode than for a platinum electrode [14,15].…”

“…Similar results have been observed for a platinum anode [14,15]. The initial rate of this reaction is, however, much lower for a DSA | electrode than for a platinum electrode [14,15].…”

“…5) and decreases with increasing initial NaC1 concentration (Fig. 6) and, moreover, is affected by the nature of electrode material [14,15]. These results cannot be well explained by the model of Ibl and Landolt, but agree with a direct electrochemical oxidation of chloride to chlorate without a dissolved hypochlorite species as intermediate.…”

“…The initial rate of chlorate formation has been explained by hydrolysis of molecular chlorine in a reaction layer at the anode [16,17]. It has been found that both ~b4, 0 and q~ox,0 increase strongly with decreasing Cl,0 [14,15]. Consequently, the initial rate of chlorate formation ~b4,0 increases with decreasing pH at the anode, whereas the equilibrium concentration of hypochlorite decreases with decreasing pH [16,17].…”

“…This high potential is achieved under extreme conditions of electrolysis, that is a solution with a low concentration of NaC1 at very high current densities. Under these conditions the direct electrochemical oxidation from chloride to chlorate has been proposed [14,15] in the first part of this section and in [14,15].…”