Preparation of a Au SERS substrate and its application in the in-situ Raman spectroelectrochemistry study of Li2CO3-K2CO3 molten salt

Molten carbonate is often used as a medium for the decomposition of carbon dioxide to produce carbon and oxygen. In-situ Raman spectroelectrochemistry is an effective means to study species changes and the electrochemical reaction mechanism at the electrode-electrolyte interface. In this paper, a Au surface-enhanced Raman spectroscopy (SERS) substrate was prepared by an electrochemical oxidation-reduction cycle (ORC) process, and the reaction mechanism and intermediate species on this kind of Au SERS electrode in a Li2CO3-K2CO3 molten salt were studied. The prepared Au SERS substrate has a SERS factor of 1.37x 10(4), and it presents excellent uniformity and long-term stability. Although the SERS effect of the Au substrate gradually weakens as the temperature increases, it maintains an acceptable SERS factor of 8.76x 10(2) after a high-temperature treatment at 873 K. The cyclic voltammogram result shows that carbon reduction preferentially occurs on an Au electrode during the cathodic electrochemical process in Li2CO3-K2CO3 molten salt. In-situ Raman spectroscopy confirms the existence of the intermediate peroxide ion (O-2(2-)) during the electrochemical reduction process.