Pd cocatalyst on Sm-doped BiFeO3 nanoparticles: synergetic effect of a Pd cocatalyst and samarium doping on photocatalysis

Abstract

To explore the synergetic effect of rare earth doping and noble metal cocatalyst loading on the photocatalytic activity of BiFeO₃ (BFO), in this work, novel Pd cocatalyst-loaded and Sm-doped BFO (Pd/BSFO) composite photocatalysts containing different Pd loading contents were successfully prepared by using a sol–gel method followed by an impregnation process. The experimental results revealed that the rhombohedral structure of BFO was distorted by Sm substitution, and Pd cocatalyst nanoparticles were uniformly deposited on the surface of BSFO particles with the formation of a heterojunction at the interface between Pd and BSFO. Compared to the BFO, BSFO and Pd/BFO sample, the Pd/BSFO samples exhibited improved UV-vis spectral absorption ability and significantly enhanced photocatalytic activities for the photodegradation of methyl orange or a colorless compound (i.e., phenol) under visible light irradiation. When the Pd loading amount on the surface of BSFO was 1.5 wt%, the optimal photocatalytic degradation efficiency was achieved. The enhanced photocatalytic activity of the Pd/BSFO photocatalyst could be attributed to the increased optical absorption, the efficient charge transfer and separation as well as the suppressed recombination of photogenerated electron–hole pairs derived from the Sm dopant trapping level and the heterojunction formation of the Schottky barrier between BSFO and the Pd cocatalyst in Pd/BSFO, as verified by photoluminescence (PL) emission spectra, photocurrent action spectra and electrochemical impedance spectra (EIS). On the basis of the calculated energy bands and trapping experiments, the photocatalytic mechanism was also discussed.