Mapping the Distribution of Potential Gradient in Bipolar Electrochemical Systems through Luminol Electrochemiluminescence Imaging.

Bipolar electrochemistry has been regarded as a powerful and sustainable electrochemical process for the synthesis of novel functional materials. The appealing features of this electrochemical technology, such as the wireless nature of the bipolar electrode (BPE) and the possibility to drive simultaneously electrochemical reactions on multiple BPEs placed in the same electrochemical cell, together with the possibility to change the shape and positioning of the driving electrodes, give significant freedom to design reaction systems. Nevertheless, the cell geometry dramatically affects the distribution and intensity of the potential gradient generated on the BPE surface and its monitoring is hampered due to the wireless nature of the BPE. In the present study, we propose the use of electrochemiluminescence (ECL) as an electrochemical imaging technique to map the distribution of potential gradient in bipolar electrochemical cells with different geometries. The proposed approach exploits the strong ECL emission of luminol/hydrogen peroxide (H2O2) system generated at the anodic pole of the BPE, when the total applied voltage (Etot) is strong enough to trigger the electrochemical reaction. Since luminol ECL emission is rather intense and relatively stable, the evolution of the potential distribution as a function of Etot can be monitored using a digital camera, allowing the elucidation of the potential distribution profile in every bipolar configuration. The suggested approach represents a valuable and reliable method to map the potential gradient in bipolar electrochemical systems and can be readily employed in every type of bipolar configuration.