The influence of crystal structure on the photoresponse of iron–titanium oxide electrodes

The photoelectrolytic decomposition of water using various iron-titanium oxide semiconducting electrodes appears to be influenced by the details of the electrode crystal structure arrangements. The structures of Czochralski grown ilmenite, FeTiO₃ (a = 5.087, c = 14.042 Å), and spinel Fe₂TiO₄ (a = 8.509 Å) have been reexamined and refined (R < 0.05) with Mo Kα intensity data. In ilmenite, the Fe and Ti atoms are ordered in alternating layers perpendicular to the c axis while, in spinel, the best agreement is found with disorder of the metal sites. This suggests a simple model based on the structural arrangement of chromophores which explains the photoresponse behavior of such electrode materials.