SCAN-Lab Technical Notes 02: Practical methods to correlate the SVP voltage to a current at a sample’s surface

Introduction

The Scanning Vibrating Probe (SVP) experiment, also called the Scanning Vibrating Electrode Technique (SVET), measures the IR drop that exists in solution in a plane above a metallic sample. Electrochemically active sites at the sample’s surface will cause an ionic current (I) to flow through the electrolyte media. The electrolyte is conductive and so has some resistance (R) associated with it. Ohm’s Law relates that V = IR, so a measurement of voltage is the same as measuring the product of the current and the resistance. Therefore, the SVP technique measures a parameter that is a result of electrochemical activity at the sample’s surface; however, it does not actually measure electrochemical activity at the surface. Several SVP users have requested assistance in correlating that measured SVP response (a voltage in a XY plane some distance from the surface) to the actual electrochemical events at the sample’s surface (a current).