Detection of electrooxidation products using microfluidic devices and Raman spectroscopy

• Main Author: Li, Tianyu
• Other Authors: Harrington, David A
• Format: Others
• Language: English; en
• Published: 2020
• Subjects: Microfluidic devices; Raman spectroscopy; Electrocatalysis; Glycerol electrooxidation; Reaction mechanism; Printed circuit boards; In-situ quantitative detection
• Online Access: http://hdl.handle.net/1828/12107

Microfluidic flow devices coupled with quantitative Raman spectroscopy are able to provide a deep insight into the reaction mechanism and kinetics of electrocatalytic reactions. With a microfluidic flow device made with glass microscope slides and polymer building blocks, the feasibility of this technique was examined by methanol electrooxidation reaction with a Pt working electrode. Pre-calibration of the Raman peak area was done with solutions of known concentrations of methanol and its major oxidation product, i.e., formate, which enabled the time-dependent Raman spectra taken during the reaction to be converted to time-dependent concentrations. These were interpreted in terms of a model with one-dimensional convection and the reaction kinetics. An improved version of this technique was then applied to a comparative study of different alcohols with Ni-based electrodes. This showed the production of formate as the major product from the oxidation of alcohols with vicinal OH groups, leading to the discovery that C-C bond dissociation is a major reaction pathway for vicinal diols and triols if Ni electrocatalysts are used. It is also suggested that the cleavage of C-C bonds is the rate-determining step. The potential use of printed circuit boards (PCB) in the next generation of a novel microfluidic device was explored, as PCB have advantages over regular electrochemical microfluidic substrates, such as simpler electrode fabrication strategies, more wiring layers, and customization of size and shape of electrodes. Pretreatments and electrodeposition protocols of nickel, silver, palladium and platinum on PCB were successfully developed, together with four types of PCB-based microfluidic devices designed with an open-source PCB design software. This work establishes a new electrochemical microfluidic platform for online and in-situ monitoring of electrocatalytic reactions, which can quickly determine the reaction mechanism and kinetics. === Graduate