Effect of Bismuth Dopant on the Photocatalytic Properties of SrTiO3 Under Solar Irradiation

Abstract

This work presents the structural, morphological and photocatalytic properties of pure SrTiO 3 (STO) and Bismuth doped STO. Several Bi doped samples were synthesized using Bi concentrations from 0.5 to 5 mol% and the sol-gel method. According to the X-ray diffraction analysis, all the samples presented cubic phase. The Scanning electron microscopy (SEM) showed that the samples without dopant or with low Bi concentration (0 and 0.5 mol%) presented a quasi-spherical morphology. The sample doped with 1 mol% of Bi presented mainly a rod-like morphology, while the samples doped with 2 and 5 mol% showed a mixture of quasi-cubic particles and rod-like particles. The absorbance experiments demonstrated that the introduction of Bi in the STO host extended the light absorption in the visible region and decreased the band gap of STO. Both effects benefited the photocatalytic properties of STO:Bi powders. In fact, the photocatalytic evaluation of the STO and STO:Bi powders under natural solar light revealed that total degradation of methylene blue (MB) can be produced only by the sample doped with 1 mol%. Scavenger experiments were also carried out using teraphtalic acid and benzoquinone in order to figure out which oxidizing agent (OH• radicals or O 2 − ) is producing the degradation of MB dye and found that the OH• radicals are the dominant agent. Since the STO:Bi powders can be activated by solar light for the photocatalytic degradation of MB, these powders could be a low cost option for the degradation of dyes in water treatment plants.

Carbon/Mn3O4/SrTiO3 microsphere photocatalyst for the efficient removal of high‐concentration methylene blue from water

“…In addition, a large amount of H + reacted with Mn 3 O 4 , reducing the catalytic degradation performance of the composite 51 . When the pH exceeded 7.0, the adsorption capacity of the composite decreased because of the competition between the high‐concentration hydroxide ions and MB molecules in the solution 28,32 . The photocatalytic degradation of MB on the MC/Mn 3 O 4 /SrTiO 3 composite at different solution pH values also followed pseudo‐first‐order kinetics.…”

“…However, when the dye concentration is extremely high, the relative residual amount of dye molecules in the solution is high after the adsorption equilibrium is reached. Photons reaching the surface of the catalyst are reduced due to the screening effect of the excess organic substrate 17,28,50 . The photocatalytic MB degradation on the MC/Mn 3 O 4 /SrTiO 3 composite under different initial concentrations of the MB solutions followed pseudo‐first‐order kinetics [Fig.…”

“…However, the photogenerated holes (h + ) generated in the VB of SrTiO 3 move to the VB of Mn 3 O 4 , and they react with H 2 O molecules to generate the strong oxidizer •OH. In addition, MB molecules are photosensitive and can absorb light during photoirradiation 28,55 . The excited hot electrons of the MB molecules adsorbed on the composite surface are transferred to the CBs of SrTiO 3 and Mn 3 O 4 , and to MC.…”

“…However, SrTiO 3 and Mn 3 O 4 powders at the nanometer level also have some issues: (i) they tend to aggregate in water at high concentrations, 27 (ii) they are difficult to separate completely from the aqueous solution 28 and (iii) they are difficult to recycle. To overcome these problems, it is necessary to find an inert and suitable carrier matrix 29 .…”

Visible-Light-Driven AO7 Photocatalytic Degradation and Toxicity Removal at Bi-Doped SrTiO3

“…Hou et al [ 30 ] and Liu et al [ 31 ] reported that through the Cr-doping of SrTiO 3 , E g of 2.32–2.12 eV and lower than 3.2 eV were obtained, respectively. Comparable lowering of E g of SrTiO 3 was also observed by doping it with Mn (2.76 eV) [ 32 ] and Bi (2.6 eV and 3.04 eV) [ 33 , 34 ].…”