New probes to surface free charge at electrochemical interfaces with platinum electrodes

Abstract

The free charge is a key variable dominating the properties of the interphase between a metallic electrode and an electrolytic solution. However, its determination in the case of platinum electrodes is not straightforward. Here, we review some of the experimental and computational strategies that can be used to gain information about the free charge in these interphases. First, we discuss the influence of the free charge on some reactions of technological interest. Then, we demonstrate the usefulness of peroxodisulfate (PDS) reduction as a probe reaction sensitive to the free charge on platinum electrodes. The comparison with other strategies, based on either CO displacement, measurements of the potential of maximum entropy of the interphase or N2O reduction, validates the consistency of this approach. Finally, it is remarked how the use of PDS reduction as a surface probe evidences the existence of a non-monotonic behavior in the variation of the charge as a function of potential on platinum electrodes.