Electrokinetic Streaming-Current Methods to Probe the Electrode-Electrolyte Interface under Applied Potentials

Abstract

At an electrified interface of metal and electrolyte ion concentration in diffuse layer is different from the bulk and is impacted by metal charge. The double layer structure can significantly enhance local ionic conductivity. Understanding the conductivity enhancement with conventional electrochemical measurements is challenging, however electrokinetic experiments can be more useful in probing local ionic conductivities. We used streaming current experiments for a range of pH values to measure zeta potential at metal-electrolyte interfaces. We extend the method by incorporating a three-electrode electrochemical cell where the potential of the metal can be varied. By using a range of applied potentials between -200 and 800 mV (vs. standard hydrogen electrode) we explored how surface charging of Au electrode affects zeta potential. An inflection point is observed on the plot of zeta potential against applied potential and this point is believed to be a potential of zero charge of the electrode. Using the G...