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 ringlsolid 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 N-2(+) ion currents, measured by the mass spectrometer, i(N-2(+)), 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(N-2) did not increase monotonically with the flow rate, v(f), reaching instead a maximum and then decreasing to values independent of v(f). This behavior has been attributed in part to hindrances in the mass transport of gases through the porous materials.