Search

SrTiO3 photocatalysts have been widely applied in overall water splitting reaction for their reasonable redox potential, whereas preventing the defects is crucial to improve the transition of photoexcited carriers influencing the photocatalytic performance. The defects in perovskite-type SrTiO3 were mainly Ti3+ and oxygen vacancies. Thence, little Ta5+ was designed to be doped in the B site for modulating the defect concentration. A series of advanced characterizations demonstrated that Ta5+ is helpful for Al3+ to penetrate the SrTiO3 lattice through lattice distortion, decreasing the Ti3+ defects. Meanwhile, the doping of slight Ta5+ facilitates the decrease in oxygen defect concentration, due to the formation of {Ta5+–O–Al3+}. Photoluminescence spectra and time-resolved fluorescence spectroscopy uncover that the charge carrier separation of SrTiO3 was enhanced by slight Ta5+. However, the excessive Ta5+ greatly promoted form the oxygen defect and Ti3+ species, leading to severe recombination of photogenerated carriers, which significantly reduced the photocatalytic activity. As a result, the optimized sample showed significant improvement in photocatalytic activity compared to the pure SrTiO3. [ABSTRACT FROM AUTHOR]

Decreasing the Ti3+ defect concentration in SrTiO3 is recognized as the focus of seeking a perfect photocatalytic activity. However, the defect‐engineered SrTiO3 by doping different low‐valence metal ions have no similarly good activity in overall water spitting, of which the reason has not been determined. Here, Na+, K+, and Cs are deliberately doped in SrTiO3 to obtain a close low‐level concentration of Ti3+ defect for comparison. An interesting phenomenon is found that the K‐doped SrTiO3 has a higher Ti3+ concentration than others but with a better intrinsic photocatalytic activity. The analysis of band structure and charge‐carriers behavior indicates the formation of a deep‐state defect in Na or Cs‐doped SrTiO3, leading to a decrease in photocatalytic activity. With the density functional theory calculation and synchrotron radiation characterization, the differences in A‐site‐metal ionic polarization are found to localize some defect charge, accompanied by uneven structural relaxation. As a result, the deep‐state defect can form in the area containing some group of atoms around the higher‐polarization metal ions, limiting the activity. This study further complements the important effect of doping ions on defect state in addition to the Ti3+ defect concentration in theory, for designing defect engineering in SrTiO3. [ABSTRACT FROM AUTHOR]

In the preparation of SrTiO3 photocatalysts, the flux treatment in corundum crucible typically increases the crystallinity and promotes Al3+ into the perovskite structure, responsible for the decrease in the concentration of Ti3+ defects. As a result, they can give a better performance in the water-splitting reaction. Thence, the selection of flux medium is crucial, and the insight of its effect on the SrTiO3 nanoparticles can give guidance for designing the synthesis process. Here, we respectively use LiCl, NaCl, KCl and SrCl2 as the flux medium assisting the preparation of SrTiO3. Combining characterizations and photocatalysis evaluations, we found that the size of cations had an influence on the SrTiO3 phase structure, and the thermal conductivity of chloride salts had an effect on the Al-doping amount into SrTiO3. Considering the two aspects, SrCl2 is the more appropriate flux medium in synthesizing SrTiO3 photocatalysts. [ABSTRACT FROM AUTHOR]