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

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.