PHOTOEFFECTS AT THE POLYCRYSTALLINE PYRRHOTITE ELECTROLYTE INTERFACE

Polycrystalline layers of pyrrohotite (Fe0.9S) mixed with PTFE and triton have been produced through a screen-printing method, followed by pressure and thermal (N2) treatments. The effect of the heat treatment as well as of the organic binders on the solid state and surface characteristics of the pyrrhotite powders and electrodes, has been analysed by XRD, XPS and Mössbauer spectroscopy. The pyrrhotite electrodes showed behavior as photoactive n-type semiconductors giving rise to a photopotential of about 200 mV in I- and Fe2+ containing solutions. Although the electrochemical corrosion was greatly inhibited by PTFE, the presence of a photocorrosion process was monitored at the illuminated electrode in presence of the redox electrolytes. A discussion is given as to explain the electrode behavior. Hypotheses related with its structure property are made. © 1990.