Q2. What is the current baseline at the ring electrode?
In this case, the current baseline at the ring electrode is related to the steady current of the hydrogen evolution reaction (HER) at Es. The amount of soluble Pb(I1) species produced at the disc lowers considerably along the potential cycling.
Q3. What is the contribution of jr to the decay of current?
as the transfer of cations through the film is a slow process, the contribution of jr explains the slow decay of current following the current peak.
Q4. What is the cathodic current contribution to the ring electrode?
It is worth noting that the cathodic current contribution to the ring electrode shows a relatively sharp and somewhat asymmetric peak at E, = -0.985 V, close to the inflection point which can be observed in the ascending branch16r, , , , , ,,: __I v: 0.02&-' (All “I 1-7~5-k--),:Orpm 1 j I---lw:500rpm );
Q5. What is the effect of a shifted value of ED on the current transients?
As the value of ED is shifted up to E, = -0.94OV, the current transient at the ring becomes sharper, and the electroreduction charge derived from these transients diminishes (Fig 6a, b, right).
Q6. What is the kinetics of the electroformation of PbSO, layers?
These cations contribute to the growth of a PbSO, layer at the PbSOJsolution interface through chemical precipitation when the concentration of Pb2+ cations adjacent to the electrode exceeds the supersaturation concentration.
Q7. What is the kinetics of a PbS04 layer?
On the other hand, within the H,SO, concentration and pH ranges covered in this work the kinetics of a PbSO., layer formation apparently remains independent of the solution composition, except that the aj&W2 slope increases as the pH of the electrolyte solution is decreased[22].
Q8. How can the rrde determine the soluble Pb species?
Pb(I1) soluble species produced at the Pb disc at v = 0.02OV s-l, at different values of w, could be determined through the corresponding electroreduction reaction at the Pb ring electrode.
Q9. What is the value of k related to the nonconducting PbSO, layer?
the value of k, related to the nonconducting PbSO, layer formation, exhibits a complex potential dependence (Table l), which at present is diilicult to interpret because of the uncontrolled precipitation of Pb2+ ions as PbSO., from the solution nearest to the electrode.
Q10. What is the average density of the PbS04 layer?
No is the number of nuclei formed instantaneously, k is the average film growth rate constant and M, p and h are the molecular weight, the density and the average height of the PbS04 layer, respectively.
Q11. What is the effect of the surface pretreatment of Pb electrodes?
The voltammetric anodic (4.) and cathodic (qJ apparent charge densities obtained from the first triangular potential scan depend on the surface pretreatment of Pb electrodes, but this influence practically disappears in the subsequent scans.