Design and Characterization of an On-line Electrochemical Mass Spectrometry System for Measurement of Multi-Step Reaction Kinetics

A micoreactor system for variable temperature measurements of electrochemical reaction kinetics is described. The reactor was made from a silicon wafer, in which fluid channels were etched, mated to a glass wafer that contained vapor-deposited Pt and Pd electrodes. A Teflon membrane, placed over an opening in the silicon wafer allowed volatile reaction products to diffuse into an attached vacuum system for detection by mass spectrometry. System response was characterized with computational fluid dynamics and conductance measurements in the vacuum system. Performance of the reactor is demonstrated by measurements of electrooxidation of methanol on a thin-film Pt electrode at 0.6 V vs. Pd/H and room temperature followed by post-reaction stripping of adsorbed CO remaining from the methanol reaction. The results show that the reactor is capable quantitative measurement of CO2 produced during methanol reaction and CO oxidation and illustrate the steps needed to improve system response.