Electrochemistry and electrogenerated chemiluminescence with a single faradaic electrode

We describe an electrochemical cell containing a single faradic electrode (a Pt ultramicroelectrode) and a blocked (polarized) electrode (Si with an insulating SiO2 film) that served as a capacitive counter electrode. When a bias was applied between the two electrodes, a current was observed from a faradic process at Pt and a capacitive current at the blocking electrode. A steady charging current was obtained when the solution was moved along the insulator to continuously contact fresh surface (emersing a layer of charged ions and electronic countercharge into the gas phase). Electrogenerated chemiluminescence was clearly observed from a system containing Ru(bpy)(3)2+ in this kind of cell under pulsed excitiation, demonstrating that faradaic reactions can be carried out in an electrochemical cell without generation of any products at a counter electrode. The use of such a system for coulometric addition of desired species in nanosystems and in synthesis is suggested.