Electrosynthesis and physicochemical properties of Fe-doped lead dioxide electrocatalysts

Doping of electrodeposited PbO2 with Fe3+ and Fe3+ + F- is investigated wit h the aim to produce electrodes of improved catalytic activity and stabilit y for use in processes at high positive potentials. The amount of Fe incorp orated into PbO2 depends on two main factors; (i) the charge of the electro de surface and (ii) the charge of Fe(III) species. Surface analysis data sh ow substantial differences in the physicochemical properties of Fe-doped an d (Fe, F)-doped PbO2 in comparison with undoped oxide. In particular, X-ray photoelectron spectroscopy (XPS) measurements show a marked decrease in th e signal due to adsorbed oxygen species, water and hydroxyl groups. On the basis of these results and of tritium radioactive tracer measurements, it i s proposed that incorporation of the foreign species in PbO2 occurs at defe ct sites: F- replaces OH groups while Fe3+ can replace Pb(II) or Pb(IV) at low and high temperature, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.