Herrmann-Geppert, I.; Bogdanoff, P.; Radnik, J.; Fengler, S.; Dittrich, T.; Fiechter, S.: Surface aspects of sol-gel derived hematite films for the photoelectrochemical oxidation of water. Physical Chemistry Chemical Physics 15 (2013), p. 1389-1398
10.1039/c2cp42651j

Abstract:
a-Fe2O3 (hematite) photoanodes for the oxygen evolution reaction (OER) were prepared by a costefficient sol–gel procedure. Due to low active photoelectrochemical properties observed, it is assumed that the sol–gel procedure leads to hematite films with defects and surface states on which generated charge carriers are recombined or immobilized in trap processes. Electrochemical activation was proven to diminish unfavourable surface groups to some extent. More efficiently, a plasma treatment improves significantly the photoelectrochemical properties of the OER. X-ray photoelectron spectroscopy (XPS) analysis reveals an oxygen enriched surface layer with new oxygen species which may be responsible for the improved electrochemical activity. Due to surface photovoltage an increased fraction of transferred charge carriers from these newly produced surface defects are identified