Visible light photocatalytic activities of nitrogen and platinum-doped TiO2: Synergistic effects of co-dopants

Abstract

The visible light photocatalytic activity of nitrogen doped TiO2 (N-TiO2) was enhanced with co-doping of Pt ions for the oxidative and reductive degradation of model substrates in gaseous and aqueous phases. The synthesized samples were characterized by various techniques (diffuse reflectance UV–Vis, XPS, XRD, FT-IR, HR-TEM, EDX and laser flash photolysis spectroscopy). The co-doping of N and Pt of TiO2 (Pt,N-TiO2) significantly enhanced the degradation of acetaldehyde (gas phase), and trichloroacetate (TCA) (aqueous phase), and the reduction of Cr(VI) (aqueous phase) under visible light (λ>420nm). The observed visible light photocatalytic activity of Pt,N-TiO2 was markedly higher than the singly-doped TiO2 (Pt-TiO2 or N-TiO2). A time-resolved diffuse reflectance (TDR) study found that the presence of the different oxidation states of Pt (2+ and 4+) plays a crucial role in the charge trapping and transfer dynamics in Pt-TiO2. The TDR study of Pt,N-TiO2 further revealed that the synergistic effect of co-doping is attributed to the combined contribution of each dopant. Finally, the first principle calculations for the doped TiO2 suggested that the electronic interaction of Pt and N in TiO2 facilitates the charge carrier mobility and reduces the undesired recombination, leading to enhanced photocatalytic activity.