In order to gain a greater understanding of the ECL mechanism, we use finite element digital simulations to explicitly model each reaction step. This was done for an organometallic ECL standard, tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)32+), and tripropylamine (TPA), where the simultaneous oxidation of Ru(bpy)32+ and TPA result in the generation of the excited state Ru(bpy)32+*. The geometry and reaction conditions were chosen to match experimental data from our previously developed cuvette based system. Comparison of simulated voltammetry and ECL emission both agreed well with the experimental data, validating the experimental results and also giving insight into the impact of the confined cuvette geometry on the observed voltammetry. Investigations into the simulated concentration profiles also revealed the ECL emission to be confined close to the electrode surface, and so the impact of side reactions at the counter electrode could be omitted. Importantly, each step in the ECL process could be individually analysed and quantified in order to provide a greater understanding of the mechanism as a whole.
Figure 1: A) Simulated concentration of the excited state luminophore Ru(bpy)32+* at the position of peak ECL emission. B) Comparison of the experimental ECL emission peak with the simulated concentration of Ru(bpy)32+*, showing good agreement.