Catalytic reduction of nitrate during electrodeposition of thallium from Tl3+ solution

The voltammetric response of vitreous carbon electrodes in nitrate solution in the presence of Tl3+ shows the reduction of Tl3+ in two stages, to Tl+ and to metallic thallium, respectively. Nitrate ions are reduced at high rates during the second stage, concurrently with Tl deposition. The catalytic current varies with the concentration of nitrate, but is virtually independent of the Tl3+ concentration. No nitrate reduction occurred when Tl deposition was carried out in a single stage from Tl+ solution, nor during reduction of Tl3+ to Tl+. The results obtained indicate that Tl2+, arising from disproportionation of Tl3+ and Tl0 to yield Tl+, mediates the catalytic reduction of nitrate to ammonia during Tl electrodeposition from Tl3+ solutions.