Miyoshi Akinobu, Kuwabara Akihide, Maeda Kazuhiko
Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1-NE-2 Ookayama, Meguro-ku, Tokyo 152-8550, Japan.
Japan Society for the Promotion of Science, Kojimachi Business Center Building, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083, Japan.
Inorg Chem. 2021 Feb 15;60(4):2381-2389. doi: 10.1021/acs.inorgchem.0c03262. Epub 2021 Jan 26.
Nitrogen/fluorine codoping of rutile TiO was recently reported to be effective for introducing visible-light absorption, and the resultant TiO:N,F worked efficiently as an O evolution photocatalyst in a Z-scheme water-splitting system. Although an increase in the amount of nitrogen doped into rutile TiO lattice in the presence of fluorine was experimentally demonstrated, the role of fluorine in the system remained unclear. Here, we report a computational study on TiO:N,F through the construction of supercell models with substitutional defects to reveal the atomic arrangement of the material and the electronic band structure. Calculations for all possible structures of nitrogen/fluorine and nitrogen/oxygen-vacancy relative positions revealed that the defect complexes were preferentially located on the (110) plane and that the distance between defects did not have a strong correlation with the formation energy. The present work also showed that although fluorine did not directly contribute to the narrowing of the band gap of TiO:N,F, the fluorine activity of the synthetic atmosphere promotes the formation of substitutional defect complexes of nitrogen/fluorine for anion sites. This eventually increases the amount of nitrogen incorporated into the rutile TiO lattice and also results in reduction of the amount of oxygen vacancy, which is in qualitative agreement with our previous result of transient absorption measurement for rutile TiO:N,F. The role of fluorine in TiO:N,F is thus clarified through our systematic first-principles calculations.
最近有报道称，金红石型TiO2的氮/氟共掺杂对于引入可见光吸收是有效的，并且所得的TiO2:N,F在Z型水分解系统中作为析氧光催化剂能高效工作。尽管通过实验证明了在氟存在的情况下，掺杂到金红石型TiO2晶格中的氮含量有所增加，但氟在该系统中的作用仍不清楚。在此，我们通过构建具有替代缺陷的超晶胞模型，对TiO2:N,F进行了计算研究，以揭示该材料的原子排列和电子能带结构。对氮/氟和氮/氧空位相对位置的所有可能结构的计算表明，缺陷复合体优先位于(110)面上，并且缺陷之间的距离与形成能没有很强的相关性。本研究还表明，尽管氟并没有直接导致TiO2:N,F的带隙变窄，但合成气氛中的氟活性促进了氮/氟替代缺陷复合体在阴离子位点的形成。这最终增加了掺入金红石型TiO2晶格中的氮含量，同时也导致氧空位数量的减少，这与我们之前对金红石型TiO2:N,F进行瞬态吸收测量的结果在定性上是一致的。因此，通过我们系统的第一性原理计算，阐明了氟在TiO2:N,F中的作用。
