FORMATION AND CHEMICAL DISSOLUTION OF LEAD-OXIDE IN ALKALINE-SOLUTIONS

The anodic behavior of the lead electrode was studied in 1 M NaOH solu tion at potentials (E) more cathodic than PbO2 formation. A photocurre nt appears when a PbO film is formed on the surface at E > -0.6 V (aga inst a mercury-mercuric oxide electrode in the same solution); it is t ransient in character because of increasing film thickness delta. The photocurrent increases with delta at values of delta below the depth, alpha-1, of light absorption, but it decreases with increasing delta w hen delta > alpha-1. In the steady state when delta is time-invariant, the rate of PbO formation is equal to its rate of dissolution, which is 10(-7) g-eq/s.cm2, in harmony with independent measurements.