Porous Teflon Ring-Solid Disk Electrode Arrangement for Differential Mass Spectrometry Measurements in the Presence of Convective Flow Generated by a Jet Impinging Electrode in the Wall-Jet Configuration

A porous Teflon ring|solid disk electrode is herein described specifically designed for acquiring online mass spectrometric measurements under well-defined forced convection created by liquid emerging from a circular nozzle impinging on the disk under wall-jet conditions. Measurements were performed for the oxidation of hydrazine, N₂H₄, in a deaerated phosphate buffer electrolyte (pH 7) on Au, a process known to yield dinitrogen as the product. The N₂⁺ ion currents, measured by the mass spectrometer, i(N₂⁺), as well as the corresponding polarization curves recorded simultaneously displayed very similar s-like shapes when plotted as a function of the potential applied to the Au disk. In fact, the limiting currents observed both electrochemically and spectrometrically were found to be proportional to [N₂H₄]. However, the limiting values of i(N₂⁺) did not increase monotonically with the flow rate, ν_f, reaching instead a maximum and then decreasing to values independent of ν_f. This behavior has been attributed in part to hindrances in the mass transport of gases through the porous materials.