Dual Optical Frequency Comb Time-resolved Spectroscopy for Surface-Enhanced Spectroelectrochemistry
Spectroelectrochemistry (SEC) is a valuable approach in the study of processes occurring at the interface between a solid electrode and the electrolyte solution. The combination of electrochemical sensitivity with molecular information finds its valuable place in applications that range from energy generation to sensing. Investigating the kinetics of electric charge dependent processes demands a great analytical sensitivity, as the observation of occurrence of molecular species at minimal amounts is the general objective. Infrared spectroscopy offers the necessary instrumental capability for time-resolved monitoring, but at the cost of colossal amounts of experimental effort as demonstrated in step-scan and rapid-scan FTIR methods. In this thesis, I present the applicability of a novel, commercial instrument based on quantum cascade laser generated optical frequency combs. The apparatus represents a promising paradigm shift with regards to interferometry-based devices. I will describe my work developing an SEC platform that is amenable to the broadband mid-IR laser source for an attenuated total internal reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) configuration. I will detail the requirements, downfalls, adaptations and solutions to establish an operational experimental platform that convenes the basis of ATR-SEIRAS with the intrinsic specificities of frequency combs. An adsorption/desorption probe system was selected to demonstrate the instrumental ability to obtain kinetic data at submillisecond range, requiring but a fraction of the experimental time and repetitions in comparison to conventional techniques such as step-scan. The electrochemical process transients are observed with microsecond time-resolution offered by the dual frequency comb SEC-ATR-SEIRAS platform.
spectroelectrochemistry, SEIRAS, frequency combs, time-resolved spectroscopy, surface processes, quantum cascade laser
Doctor of Philosophy (Ph.D.)