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<p>Oxygen vacancy creation in metal oxides is a proven strategy to enhance their catalytic functions. Oxygen vacancies in two-dimensional layered systems can drastically alter the electronic, optical, and catalytic properties of metal oxides. With this background, we created oxygen vacancies in layered rhombohedral Bi<sub>0.775</sub>Pr<sub>0.225</sub>O<sub>1.5</sub> (BPO) by intentionally introducing divalent alkaline-earth metal ions (Ca, Sr, and Ba) in place of Pr<sup>3+</sup>. The samples were synthesized by a solution combustion method and characterized extensively.&#xa0; &#xa0;Using powder X-ray diffraction and Raman spectroscopy, the extent of <i>x</i> in Bi<sub>0.775</sub>Pr<sub>0.225−<i>x</i></sub>M<sub><i>x</i></sub>O<sub>1.5</sub> (M = Ca, Sr, Ba) forming a monophasic layered structure was determined. With the progressive increase in Ca- and Sr-content in BPO, the <i>a</i>- and <i>c</i>-axes contracted and expanded marginally. With the inclusion of Ba, a substantial increase in the <i>c</i>-axis was observed. The inclusion of higher amounts of M<sup>2+</sup> (M = Ca, Sr, Ba) in BPO resulted in a new band at 612&#xa0;cm<sup>−1</sup> in the Raman spectra, attributable to oxygen vacancies. EPR spectra at room temperature confirmed the paramagnetic nature of oxygen vacancies. Using this synthetic method, Bi<sub>0.775</sub>(M<sub>1/4</sub>)<sub>0.225</sub>O<sub>1.5</sub> (M = Mg, Ca, Sr, and Ba) with a medium configurational entropy of ΔS<sub><i>mix</i></sub> = 1.38 R has been prepared in monophasic form. They were uniformly distributed in the lattice, exhibiting layered morphology. Iodine intercalation in all these layered samples was successful. The oxides and their iodine-intercalated analogs were examined for their catalytic roles in the reduction (4-nitrophenol) and oxidation (4-chlorophenol) of organic pollutants, as well as in carbon–carbon bond-forming reactions.</p>

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Oxygen vacancy enrichment in 2D-layered Bi0.775Pr0.225−xMxO1.5 (M = Ca, Sr, x ≤ 0.225 and Ba x ≤ 0.20) and their iodine intercalated analogues, leading to trifunctional catalytic applications

  • 期刊论文

  • 发表日期：

    2026年4月3日

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  • Bhagwat Singh,
  • Divya Sangwan,
  • Rajamani Nagarajan

摘要

Oxygen vacancy creation in metal oxides is a proven strategy to enhance their catalytic functions. Oxygen vacancies in two-dimensional layered systems can drastically alter the electronic, optical, and catalytic properties of metal oxides. With this background, we created oxygen vacancies in layered rhombohedral Bi0.775Pr0.225O1.5 (BPO) by intentionally introducing divalent alkaline-earth metal ions (Ca, Sr, and Ba) in place of Pr3+. The samples were synthesized by a solution combustion method and characterized extensively.   Using powder X-ray diffraction and Raman spectroscopy, the extent of x in Bi0.775Pr0.225−xMxO1.5 (M = Ca, Sr, Ba) forming a monophasic layered structure was determined. With the progressive increase in Ca- and Sr-content in BPO, the a- and c-axes contracted and expanded marginally. With the inclusion of Ba, a substantial increase in the c-axis was observed. The inclusion of higher amounts of M2+ (M = Ca, Sr, Ba) in BPO resulted in a new band at 612 cm−1 in the Raman spectra, attributable to oxygen vacancies. EPR spectra at room temperature confirmed the paramagnetic nature of oxygen vacancies. Using this synthetic method, Bi0.775(M1/4)0.225O1.5 (M = Mg, Ca, Sr, and Ba) with a medium configurational entropy of ΔSmix = 1.38 R has been prepared in monophasic form. They were uniformly distributed in the lattice, exhibiting layered morphology. Iodine intercalation in all these layered samples was successful. The oxides and their iodine-intercalated analogs were examined for their catalytic roles in the reduction (4-nitrophenol) and oxidation (4-chlorophenol) of organic pollutants, as well as in carbon–carbon bond-forming reactions.