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, N ₂H ₄, 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 [N ₂H ₄]. 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.