Ruthenium Dioxide as Cathode Material for Hydrogen Evolution in Hydroxide and Chlorate Solutions

Ruthenium dioxide as electrocatalyst on an activated cathode for chlorate production was investigated with respect to its activity towards hydrogen evolution, hypochlorite reduction, and chlorate reduction, respectively. Investigations were made in the presence, as well as in the absence, of a chromium hydroxide film in 1 M and in typical chlorate electrolyte. Low overvoltages for hydrogen evolution were found and, at technical current densities, an effect of catalyst coating thickness. Commercial DSA® electrodes with as the active compound were tested as cathodes and were less active but more stable than the coatings produced by us. Hypochlorite and chlorate were reduced in the absence of chromate, chlorate reduction being fast on ruthenium dioxide compared to the other electrode materials and by far the dominating cathodic reaction in chlorate electrolyte without chromate and hypochlorite at 70°C, 3 kA/m 2 .