Understanding the impact of electrochemical phenomena on the chemical reactivity of molecular systems at electrified interfaces is necessary to pave new routes for the utilization of renewable energy in a wide variety of (electro)chemical transformations of interest to chemical manufacture, environmental remediation, and energy conversion. Acid-base interactions are one of the most fundamental chemical processes affecting reactivity, but it is well known that the behavior of these chemical systems differs significantly on the bulk of a solution and at electrified interfaces. In this work, we hypothesized that interfacial polarization could modulate the acid-base lability of redox-active complexes (i.e. redox-active adducts) at electrode surfaces, thus modifying their redox response in unexpected ways. The ability to control the chemical interplay of such complexes at the electrochemical interface would create new opportunities to use electrochemical processes to drive chemical transformations on demand via the applied potential. <br/>In order to detect changes in surface chemical reactivity with high versatility with respect to the applied potential we turned to scanning electrochemical microscopy (SECM). SECM allows us to detect and prompt changes in the chemical speciation at the electrode surface as different potentials are applied to a substrate electrode. Using this technique, we investigated the signatures resulting from redox-active adducts subject to different polarizations. Our results indicate a strong dependence of the redox reactivity of these systems which cannot be explained by expectations from electron transfer theories. To complement our exploration of the electrochemical interface, we further turned to the use of multimodal SECM involving surface-enhanced Raman scattering (SERS-SECM) modes. This tool allows us to probe chemical phenomena at the electrochemical interface, adding exciting capabilities to our ability to test ideas correlating electrode polarization with modified chemical reactivity. During this presentation we will discuss both the conceptual and technical prospects of these investigations.

Exploring chemical reactivity at the polarized electrochemical interface using scanning electrochemical microscopy

ACS Spring 2022

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