Photocatalytic and photoelectrocatalytic properties of Eu(III)-doped perovskite SrTiO3 nanoparticles with dopant level approaches

Eu(III) ion dopant exhibits unique luminescence depending on the local dopant environment in a host matrix. In the present study, Eu(III)-doped strontium titanate (SrTiO3) nanoparticles were synthesized and their catalytic activities were demonstrated to examine the roles of dopants in photocatalytic CO2 reduction, photocatalytic organic pollutant degradation and photoelectrocatalytic oxygen evolution reaction. The fundamental properties were characterized by X-ray diffraction crystallography, scanning electron microscopy, high resolution transmission electron microscopy, UV-visible absorption, Raman spectroscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). CO2 reduction products were observed to be mainly methanol, CO and CH4 with minor C-2 compounds. Photocatalytic dye degradation showed the order of methyl orange < rhodamine B < methylene blue. The catalytic performances were found to be dependent on the Eu doping levels. Photoelectrocatalytic activities were tested by linear sweep voltammetry under 395 nm light which corresponds to the direct L-5(6) <- F-7(0) transition of Eu(III). Consequently, undoped SrTiO3 showed the highest enhancement in current density. Eu(III) ion was appeared to be initially doped in Sr(II) site confirmed by photoluminescence and XPS profiles. Ti(IV) oxidation state was also impacted by Eu(III) doping. The various tests demonstrated that Eu(III)-dopant could be a very useful probe for the elucidation of local environmental site and the dopant-role on catalytic activities.