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

The kinetics of PbO2 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 Ni2+/PbO2 electrodeposition is not in conflict with that of PbO2 formation in the absence of foreign species that we described earlier. Accordingly, electrochemical formation of PbO2 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 Pb2+ electrooxidation in the presence of Ni2+ 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 PbO2 show, at the same time, a high activity for O-2 evolution. Changing of the electrolyte composition and conditions of electrodeposition of PbO2 (deposition potential, temperature and pH) significantly influences the physicochemical properties of the PbO2 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 Ni2+/PbO2 electrbdes 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. (C) 2016 Elsevier B.V. All rights reserved.