Abstract
and 
were subjected to surface analyses by x‐ray photoelectron and Auger electron spectroscopy, after their use as photoanodes in polysulfide solutions. For 
samples that had a poor (ca. 2%) conversion efficiency, a rather heterogeneous surface was found, with patches rich in In, which is probably present mainly as oxide. Some 
was found as well, although the top layer was depleted in Cu, compared to a reference sample. More efficient (ca. 5%) samples showed a more homogeneous surface and even stronger Cu depletion. These changes are ascribed to additional surface treatments, viz., dipping in hot 
solution and thermal oxidation of the resultant etched surface. For 
samples, no significant exchange of lattice Se by S from the polysulfide solution is seen, in sharp contrast to what is observed for 
or 
. If sulfur is found, its presence could be correlated with the spurious occurrence of Cd (used as dopant) or Ag (used for the ohmic back contact). Cu depletion also occurs near the surface of the diselenide after use in polysulfide solution. Most of the remaining In seems to occur in indium oxide and/or indium selenide. Cu2+ was found neither here nor on the surface of the more efficient disulfide sample. It is suggested that the occurrence of an indium oxide top layer, aided by thermal oxidation of the electrode in the case of 
, has a beneficial effect on electrode performance.