(51e) Impact of Methods to Remove of Adventitious Carbon from Roughened Au for in-Situ Surface Enhanced Raman Spectroscopy of Electrocatalytic Intermediates

Surface Enhanced Raman Spectroscopy (SERS) is a promising analytical technique for probing adsorbates and catalytic reaction intermediates of electrochemical reactions. Its surface specificity, single-molecule-level resolution, and non-destructive abilities make it one of few techniques capable of probing adsorbates at the solid-liquid interface. Despite its unique capabilities, the accuracy and detection limit of SERS are hindered by the presence of adventitious carbon on SERS-active substrates. In this work, we showed that piranha or oxygen plasma cleaning are capable of removing 98% of adventitious carbon based on SERS signal from roughened gold (Au) substrates. We found that clean Au substrates produced by piranha and oxygen-plasma treatment allow accurate identification of SERS peaks for perchlorate. Furthermore, the minimum detection limit of thionine, a common probe molecule, on cleaned Au substrates is orders of magnitude lower than untreated substrates. This has important consequences for the ability of these Au substrates to detect catalytic intermediates, which typically form at low concentrations. To further demonstrate the practicality of SERS-active substrate cleaning, we performed in-situ measurements of the carbon dioxide reduction reaction (CO₂RR) on our cleaned Au substrates. Using these Au electrodes, we uncover critical insights to the CO₂RR mechanism on Au by identifying adsorbed *COOH and *COO^− intermediates. These intermediates are similar to those detected on Ag and Cu electrodes The effective cleaning treatments identified by this study will become a useful tool to properly study other electrochemical processes where carbon contaminations are a major concern (i.e. ion adsorption for CO₂RR and water electrolysis).