Insights into the Electrooxidation Mechanism of Formic Acid on Pt Layers on Au Examined by Electrochemical SERS

다국어 초록 (Multilingual Abstract)

<P>The electrooxidation of formic acid (FA) on Pt has received great attention because of its fundamental significance as a model reaction and its technical importance in fuel cells. Pt layers modified on Au surfaces were recently reported to exhibit enhanced electrocatalytic activity for FA oxidation; however, the mechanistic details have not been clearly elucidated. In this work, the mechanism of FA electrooxidation on Pt layers on Au surfaces was investigated via in situ electrochemical surface-enhanced Raman scattering (SERS). SERS-active DAR@Pt(n) substrates were prepared using the self-terminating electrodeposition of Pt on dendritic Au rod (DAR) surfaces, wherein the amount and coverage of Pt were precisely controlled by applying a different number of potential steps (n) during the electrodeposition process. The electrocatalytic activity of FA was highly dependent on the Pt coverage and thickness on DAR@Pt(n), which was investigated by electrochemical SERS. The amount of CO produced by the dehydration of FA, the potential-dependent SERS intensity variation, and the Stark slopes were examined on different DAR@Pt(n) surfaces. DAR@Pt(1) surfaces with island-type Pt layers on Au exhibited typical electrooxidation behavior that has been proposed to proceed through direct reaction pathways; however, adsorbed CO produced by dehydration was observed, indicating that the indirect electrooxidation of FA operates even on this surface. As the Pt coverage on DAR@Pt(n) increased, a greater amount of CO was produced by FA dehydration, and the adsorbed CO persisted longer in the early stage of FA electrooxidation. The direct electrooxidation of FA was mostly prohibited by the adsorbed CO initially produced by the dehydration of FA on DAR@Pt(15) with monolayer-level Pt layers. The present work provides insight into the mechanistic interpretation of FA electrooxidation on Pt-Au systems.</P>