Electrosynthesis and physicochemical properties of Fe-doped lead dioxide electrocatalysts

Doping of electrodeposited PbO2 with Fe3+ and Fe3+ + F- is investigated with the aim to produce electrodes of improved catalytic activity and stability for use in processes at high positive potentials. The amount of Fe incorporated into PbO2 depends on two main factors; (i) the charge of the electrode surface and (ii) the charge of Fe(III) species. Surface analysis data show substantial differences in the physicochemical properties of Fe-doped and (Fe, F)-doped PbO2 in comparison with undoped oxide. In particular, X-ray photoelectron spectroscopy (XPS) measurements show a marked decrease in the signal due to adsorbed oxygen species, water and hydroxyl groups. On the basis of these results and of tritium radioactive tracer measurements, it is proposed that incorporation of the foreign species in PbO2 occurs at defect 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.