Electrodeposition of Ni2+-doped PbO2 and physicochemical properties of the coating

Abstract The kinetics of PbO 2 electrodeposition from nitrate electrolytes containing nickel ions, and the influence of deposition conditions on the physicochemical properties of obtained materials, have been investigated. This study reveals that the mechanism of Ni 2+ /PbO 2 electrodeposition is not in conflict with that of PbO 2 formation in the absence of foreign species that we described earlier. Accordingly, electrochemical formation of PbO 2 occurs in four stages, two of which are electron transfer steps while the other two are chemical reactions involving formation and decay of soluble intermediates consisting of 3 and 4-valent lead species. We observed an inhibition of Pb 2+ electrooxidation in the presence of Ni 2+ that is attributable to partial blocking of the active surface sites by the adsorbed foreign cations. Interestingly though, blocked active sites that inhibit the growth of PbO 2 show, at the same time, a high activity for O 2 evolution. Changing of the electrolyte composition and conditions of electrodeposition of PbO 2 (deposition potential, temperature and pH) significantly influences the physicochemical properties of the PbO 2 deposits. In particular, the phase and chemical composition, the crystallographic orientation, the content of structural water and the nature of adsorbed oxygen-containing particles on the electrode surface. Concerning the last point, bearing direct relevance to the electrocatalytic properties, we noted that Ni 2+ /PbO 2 electrodes feature a significant increase in the amount of labile oxygen intermediates on the electrode surface which are responsible of a high electrocatalytic activity in the O 2 evolution reaction.