PIERCAT · Gap-plasmon electrochemistry coupled with photo-induced enhanced Raman spectroscopy to probe oxygen vacancy dynamics (in-situ) and hot charge carrier kinetics for photoelectrochemical CO2 reduction

Photo-electrochemical CO2 reduction (CO2 ER) is a promising technology to mitigate the ever-increasing CO2 levels in the earth's atmosphere as well as to produce chemical feedstocks simultaneously. Though tremendous research has been undertaken in the recent past to enhance the efficiency of CO2ER, still little known about CO2ER reaction pathways, selectivity, and the role of active sites, which impede the largescale implementation at the industrial level. It is well known that the surface structure strongly influences the electrocatalytic activity of electrode materials. Thus, the presence of defects, for instance, oxygen vacancies (VOs) drastically alter the surface physicochemical properties of metal oxide (MO) based electrodes and play a crucial role in defining the overall performance of CO2 ER. Therefore, it is indeed necessary to better understand the VOs formation, healing, and associated reaction kinetics. Here, I introduce photo-induced enhanced Raman spectroscopy (PIERS) coupled with gap-plasmon-assisted electrochemistry as a powerful tool to probe the VOs and associated charge transfer dynamics of MO electro-catalysts. Plasmonic nanogaps are ideal for the extreme localization of light and they generate intense electric fields in confined volumes. Such a small gap volume dramatically enhances the light-matter interaction and enables the creation of single molecule-level spectroscopic probes. Therefore, using the combination of gap-plasmon probe electrochemistry and in-situ PIERS, the current proposal aims to elucidate the underlying reaction mechanism of CO2ER at active sites (VOs). As a result, new strategies may be unveiled to design and tune the active sites on MO electrode surfaces for efficient CO2ER. Therefore, the study is not only limited to CO2ER but also provides significant insights for other important photo-electrocatalytic applications as well, for instance, fuel cells.