Response of Conductive Diamond Electrode to Pb²⁺/PbO₂ Redox Process in HNO₃ Aqueous Solution

抄録

We investigated the electrochemical behavior on the boron-doped conductive diamond electrode in HNO₃ aqueous solution containing Pb²⁺ ions. The anodic oxidation led to the formation of a PbO₂ deposit on the diamond electrode. In HNO₃ solution containing less than 10 μM (M=mol/l) Pb²⁺ ions, a clear cathodic current peak was observed on the diamond electrode in the cathodic potential scan after holding the potential at 1.80 V vs. SCE. On both the platinum and glassy carbon electrodes, it was difficult to detect a cathodic current peak exactly in the same solution because of the large background current of these electrodes. The proportional relation between the magnitude of the cathodic current peak and the concentration of Pb²⁺ ions (1-10 μM) in coexistence of Cu²⁺ and Fe³⁺ ions was obtained by use of diamond electrodes pretreated with cathodic reduction and anodic oxidation in HNO₃ solution. The diamond electrode also showed high ability to scavenge Pb²⁺ ions from the solution.