Effects of Sm and Y on the electron property of the anodic film on lead in sulfuric acid solution

The influences of Sm and Y on the electron properties of the anodic films on lead at 1.28 V(vs.SCE), 1.5 V(vs.SCE) and 1.8 V(vs.SCE) in 4.5 mol L−1 sulfuric acid are investigated by using electrochemical impedance spectroscopy (EIS), Mott–Schottky plot, galvanic polarization and photo-electrochemical technique. The results show that Sm and Y can significantly decrease the resistances of the anodic films on lead electrode at 1.28 V, 1.5 V and 1.8 V, the oxygen and hydrogen evolutions of lead electrode covered by the anodic film decrease with the addition of Sm or Y. The anodic films on lead electrode at three potentials appear an n-type semi-conductive character, the addition of Sm or Y can decrease the slope of M–S plot of the anodic film, it implying the increment of the defect density within the anodic film, which is beneficial for improving the charge–discharge behavior of the lead acid battery.

► The growth of PbO in the anodic film on lead electrode at 1.28 V in sulfuric acid was inhibited by the addition of Sm or Y.
► The passive capacity of lead electrode in sulfuric acid was improved by the addition of Sm or Y.
► The numbers of point defect in the anodic films on lead electrode at 1.28 V, 1.5 V and 1.8 V increase with increasing Sm or Y.