The effect of pre-polarization for Pt electrode on the behavior of anodic electrochemiluminescence (ECL) of luminol in alkaline solution was studied. It was found that the Pt electrode cathodically prepolarized in alkaline solution with dissolved oxygen could enhance the ECL peak at about 0.22V(vs. SCE). Moreover, it could catalyze the evolution process of oxygen at about 1.07V (vs. SCE) accompanied with a new ECL peak. However, the pre-treatment for Pt electrode in sulfuric acid solution inhibited these activities. The possible catalytic mechanism of the oxygen evolution process is proposed. In alkaline solution, the dissolved oxygen was reduced to the hydroxide ion and adsorbed on the surface of electrode, which increased the rate of oxygen evolution. The possible mechanism for the two ECL channels at the Pt electrode cathodically pre-polarized in alkaline solution is also proposed: (1) luminol anion was electroxidized to radical at 0.22V, which then reacted with the oxygen dissolved in solution and emitted light; (2) the fresh oxygen species electro- generated at 1.07V oxidized luminol anion with light emission.

Key words: PLATIMUM ELECTRODE, ELECTROLUMINESCENCE, REDUCTION