Thin layer spectroelectrochemical (RVC-OTTLE) studies of pertechnetate reduction in acidic media

The electroreduction of the pertechnetate ions has been examined in sulfuric acid solutions (0.5-4 M) using optically transparent thin layer spectroelectrochemical (RVC-OTTLE) cell. Soluble Tc(III), TcO2+ and [Tc(μ-O)2Tc]3+/4+ species with absorption bands at 420-450, 400, and 502 nm, respectively, were found to be formed during the reduction of TcO4- ions. The strongly acidic medium was found to stabilize technetium ionic forms with lower oxidation states. Spectroelectrochemical measurements performed in 4 M H2SO4 show different stability of dimeric structure of Tc(III, IV) and simple TcO2+ ions. The monooxotechnetium(IV) ions can be electrooxidized at potentials lower than 0.6 V versus Ag,AgCl(sat.) while dimeric structures of Tc, [Tc(μ-O)2Tc]3+/4+, are electrooxidized to pertechnetate ions at potentials higher than 0.8 V versus Ag,AgCl(sat.).