对 Ir-TiO2 的晶体缺陷、氧空位和相变的新见解,The Journal of Physical Chemistry C

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对 Ir-TiO2 的晶体缺陷、氧空位和相变的新见解
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2021-10-19 , DOI: 10.1021/acs.jpcc.1c07848
Vignesh Kumaravel _{1,

2} , Enrico Bianchetti ₃ , Snehamol Mathew _{1,

2} , Steven J. Hinder ₄ , John Bartlett _{1,

2} , Cristiana Di Valentin ₃ , Suresh C. Pillai _{1,

2}

Affiliation

本研究全面研究了铱 (Ir) 掺杂对 TiO ₂的氧空位、相对稳定性、微晶尺寸、表面积和锐钛矿向金红石转变的影响。Ir掺杂的TiO ₂ (Ir-TiO ₂ )是通过溶胶-凝胶技术合成的，样品在400-700°C的温度范围内退火。密度泛函理论计算表明，与原始 TiO ₂相比，Ir-TiO ₂氧空位形成的能量成本较低，形成 Ir ³⁺带隙中的状态。Ir 可以提供更多的金红石形核位点，并通过晶体应变弛豫加速金红石的形成。混合熵通过掺入 Ir 降低，这可以在低于纯 TiO ₂的正常相变温度的温度下随着吉布斯自由能的增加诱导金红石形成。与原始 TiO ₂ (600 °C)相比，Ir-TiO ₂的金红石形成可以在较低的退火温度 (400 °C)下发生，这表明通过加入 Ir 可以降低相变的活化能。由于 Ir 的存在，XPS 揭示了 Ir 4f 峰、Ir 4f _7/2 (61.96 eV) 和 Ir 4f _5/2 (64.77 eV)的自旋轨道耦合³⁺。拉曼研究表明通过 Ir 掺杂形成电荷补偿氧空位和 d 态。得出的结论是，缺陷的起源是因为掺入 Ir 可以促进金红石形核位点，从而通过应变松弛加速相变。

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New Insights into Crystal Defects, Oxygen Vacancies, and Phase Transition of Ir-TiO2

The impact of iridium (Ir) doping on the oxygen vacancies, relative stability, crystallite size, surface area, and anatase-to-rutile transition of TiO₂ was comprehensively investigated in this study. Ir-doped TiO₂ (Ir-TiO₂) was synthesized through a sol–gel technique, and the samples were annealed in the temperature range of 400–700 °C. Density functional theory calculations showed that the energy cost of an oxygen vacancy formation for Ir-TiO₂ was lower, as compared to that of the pristine TiO₂, with the formation of Ir³⁺ states in the band gap. Ir could provide more rutile nucleation sites and accelerate the rutile formation through the crystal strain relaxation. The entropy of mixing was reduced by the incorporation of Ir, which could induce the rutile formation with an increase in Gibbs free energy at temperatures below the normal phase transition temperature for pure TiO₂. The rutile formation of Ir-TiO₂ could take place at a low annealing temperature (400 °C) compared to pristine TiO₂ (600 °C), indicating that the activation energy for phase transition could be decreased by incorporating Ir. XPS revealed the spin–orbit coupling of Ir 4f peaks, Ir 4f_7/2 (61.96 eV) and Ir 4f_5/2 (64.77 eV), due to the presence of Ir³⁺. Raman studies indicated the formation of charge-compensating oxygen vacancies and the presence of d states by Ir doping. It is concluded that the defects originated because the incorporation of Ir could facilitate rutile nucleation sites and thereby accelerate the phase transition through strain relaxation.

更新日期：2021-10-28

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