Cu-substituted lanthanum ferrite perovskites: preparation, characterization and photocatalytic activity in gas-soid regime under simulated solar light irradiation

Lanthanum orthoferrites LaFeO3 nanopowders doped with 20 mol% of Sr and 0-10-20 mol% of Cu were prepared by citrate auto-combustion synthesis and investigated in terms of crystal structure, morphology, surface area and optical properties by using several characterization techniques. The band gap energy values were found to range from 2.35 eV for LaFeO3 to 1.86 eV for the samples with the highest content of copper, this trend reflects the decrease of the particle size. All powders showed photocurrent response, the highest photocurrent was obtained for undoped orthoferrite calcined at 600°C. Their physical-chemical properties were related to photoelectrochemical behaviour. The 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). Doping with 20 mol% of strontium does 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