DFT, EPR and SPR insight to the relation between photocatalytic activity and nonlinearity and anisotropy ferromagnetism of Au/Co3O4/Bi2MoO6 composites

Abstract

The combination of Surface Plasmon Resonance (SPR) effect with hetero-p-n structure has shown promising benefits to photocatalytic activity of catalysts. In this study, Au nanoparticles doped p-n hetero-structured Co3O4/Bi2MoO6 composites were synthesized and subjected to photocatalytic and photocurrent tests using visible light irradiation. The synthesized Au/Co3O4/Bi2MoO6 efficiently removed 97.2% of Methyl orange within 60 min, showing very good photocatalytic stability through leaching test. Colorless pollutant phenol degradation test verified the excellent photocatalytic activity of Au/Co3O4/Bi2MoO6. Possible influential factors such as electron transition, charge transfer, energy band gap, DOS, polarizability, SPR effect, oxygen vacancies and anisotropy permittivity were investigated through DFT, XPS, EPR, Z-scan, UV–visible spectra, ellipsometer spectroscopy and Mott-Schottky analysis. A reasonable degradation mechanism and possible pathway for Methyl orange were proposed based on the experimental results and DFT calculations. The doped Co3O4 provided active 3d electrons transition and charge transfer which increased carriers’ concentration and reduced the energy band gap, while the Au SPR enhanced internal polarization and strengthened the built-in electric field, yielding strong driving force for photo-generated electrons-holes pairs separation and consumption. In addition, magnetic Co3O4 endowed sample with room-temperature ferromagnetism which was obviously strengthened by Au NPs. The magnetism of sample was beneficial for separation and recovery in photocatalytic practical applications.