Photoelectrochemical Properties of Doped Lanthanum Orthoferrites

LaFeO3 powders doped with Sr (20 mol%) and Cu (0-10-20 mol%) were prepared by citrate auto-combustion synthesis and investigated in terms of crystal structure, morphology, surface area and optical properties. All powders showed photocurrent response in the form of a pasted and annealed electrode and as slurry electrode; the highest value was obtained for undoped orthoferrite calcined at 600 °C. Their physical–chemical properties were related to photoelectrochemical behaviour. The position of the quasi-Fermi level of electrons for all the photocatalysts calcined in the range 600–980 °C is about the same within experimental error (between −0.62 and −0.67 V with respect to Ag/AgCl reference electrode, at pH 7). Doping with 20 mol% of strontium did not influence the flat band potential of the powders, while doping with copper caused an important and reproducible change in the titration curve, indicating the presence of intermediate energy states in the samples calcined at 600 °C, but not in those calcined at 980 °C.