Visible-light-responsive hydrogen-reduced CoO_x loaded Rh/Sb:SrTiO₃ nanocubic photocatalyst for degradation of organic pollutants and inactivation of bacteria

In this work, we synthesized cobalt oxide loaded Rh/Sb:SrTiO₃-nanocube (NC) photocatalysts for organic dye degradation and bacterial inactivation. Firstly, we synthesized Rh/Sb-doped SrTiO₃ NC nanocomposite and further loaded cobalt oxide (2 wt%) via wet impregnation and followed by hydrogen-reduction treatments. Interestingly, after hydrogen heat treatment cobalt oxide-loaded photocatalysts convert into metallic Co/CoO_x-Rh/Sb:SrTiO₃ NCs. The hydrogen-treated Co/CoO_x-Rh/Sb:SrTiO₃ NCs (red) photocatalyst shows significantly high degradation efficiencies and good recyclability for Orange II dye (90.1%) and bisphenol A (99.1%) under visible-light irradiation (λ ≥ 420 nm) within 30 min. Additionally, the bacterial inactivation efficiency of Co/CoO_x-Rh/Sb:SrTiO₃ NCs (red) photocatalyst reaches about ∼97% for both Staphylococcus aureus and Escherichia coli under visible light. The enhanced photocatalytic dye degradation and bacterial inactivation activity of Co/CoO_x-Rh/Sb:SrTiO₃ NCs (red) photocatalyst was due to the delayed photogenerated charge-recombination process, generation of oxygen vacancies, and the synergistic effect of a metallic Co/CoO_x phase. Further, radical trapping experiments confirmed that the degradation of Orange II was governed by the major species, ^•O⁻₂ and h⁺. In last, the possible charge-transfer mechanisms of the photocatalytic degradation of organic pollutants, as well as the inactivation of bacteria over the Co-Rh/Sb: SrTiO₃ (red) NC photocatalyst, are presented in detail.