Potential-resolved electrochemiluminescence of ru(bpy)3(2+)/C2O4(2-) system on gold electrode.

Abstract

The electrogenerated chemiluminescence of Ru(bpy)3(2+)/C2O4(2-) system on a pre-polarized Au electrode was studied using a potential-resolved electrochemiluminescence (PRECL) method. Two anodic ECL peaks were observed at 1.22 V (vs. SCE) (EP1), 1.41 V (vs. SCE) (EP2), respectively. The effects of the concentration of oxalate and Ru(bpy)3(2+), adsorbed sulphur, CO2, O2, pH of the solution and pretreatment of the Au electrode on the two PRECL peaks were examined. The surface state of the pre-oxidized gold electrode was also studied using the X-ray photoelectron spectroscopy (XPS) technique. Moreover, comparative studies on i-E and I-E curves were carried out and a possible mechanism involving both the catalytic and the direct electro-oxidation pathways was proposed for the ECL of Ru(bpy)3(2+)/C2O4(2-) system. EPI is attributed to the Ru(bpy)3(2/3+) reaction catalysed by C2O4(2-) to generate Ru(bpy)3(2+)*. EP2 is likely because C2O4(2-) was oxidized at the electrode to form CO2(-)*, followed by reaction with Ru(bpy)3(3+) to generate Ru(bpy)3(2+)*.