Coupling Raman spectroscopy and scanning electrochemical microscopy for spectroelectrochemical analysis of electrode interfaces

Structural heterogeneity of an electrode interface causes variation in the reactivity across the electrochemically active surface. Bulk electrochemical measurements are unable to parse out the contributions to different structural motifs and how they affect surface processes, leaving the spatial correlation between structure and reactivity unobtained. Furthermore, electrochemical measurements are incapable of performing speciation of materials, meaning an electrochemical technique alone would not suffice in determining the link between structure and reactivity. This absence of information is especially hampering in cases where the composition or structure of the electrode surface changes over the course of an experiment. Ascertaining the link between reactivity and structure therefore requires new multimodal platforms able to simultaneously measure site-specific electrochemical reactivity and structural properties. To accomplish this, we constructed a spectroelectrochemical platform of combined scanning electrochemical microscopy (SECM) and Raman spectroscopy. Through alignment of a laser line to the same location of a SECM probe, the surface of a material can be analyzed in situ by co-localized, temporally matched methods. We applied this setup to study electrode interfaces of interest including redox active colloids, modified graphene layers, and single layer graphene with sublayer gold nanoparticles. In each case the instrument setup afforded information only obtainable by coupling the two techniques, demonstrating the usefulness of a spatially resolved multimodal platform for the in situ investigation of electrode interfaces