Bi掺杂NaTaO3中Bi的化学价态对其光催化性能的影响

分别采用NaBiO3和Bi(NO3)3为Bi源制备了Bi掺杂NaTaO3光催化剂，研究了Bi离子的价态对NaTaO3光催化分解水制氢性能的影响.采用X射线衍射(XRD)、拉曼光谱、X射线光电子能谱(XPS)和紫外-可见吸收光谱研究了催化剂的晶体结构、Bi离子的化学状态和催化剂的光学吸收性能.以光催化分解水制氢反应研究了Bi离子掺杂NaTaO3的催化性能. XRD结果表明，对于两个不同Bi源掺杂的NaTaO3样品， Bi离子的掺杂没有改变催化剂的单斜相结构，但拉曼光谱证实Bi离子的掺杂致使Ta–O–Ta键角偏离了180o. XPS结果表明，以Bi(NO3)3为Bi源时， Bi离子以Bi3+掺杂于NaTaO3的A位；当以NaBiO3为原料时， Bi3+和Bi5+共掺杂于NaTaO3的A位.两种不同Bi源掺杂得到的样品在紫外-可见吸收光谱中给出了相似的光学吸收，但Bi3+的掺杂对NaTaO3光催化性能影响不大，而Bi3+和Bi5+共掺杂大大提高了NaTaO3的光解水制氢性能. Bi离子取代Na离子在A位的掺杂，在NaTaO3结构中引入了能够促进载流子分离的空位和缺陷；与此同时， Bi的掺杂导致Ta–O–Ta键角偏离180o而不利于载流子迁移.对于Bi3+掺杂的NaTaO3样品，这两种作用相互抵消，使得其催化性能与NaTaO3相比没有变化；而Bi3+和Bi5+的共掺杂和高价态Bi5+的掺杂引入了更多的空位和缺陷，提高了光生电子-空穴的分离效率，从而提高了光催化产氢性能.研究表明，光催化过程中载流子的迁移是影响催化性能的重要因素，而在ABO3钙钛矿结构的A位引入高价态离子是促进光生载流子分离的有效途径.

Influence of Bi chemical state on the photocatalytic performance of Bi-doped NaTaO3

NaBiO3 and Bi(NO3)3 were used to synthesize Bi-doped NaTaO3. The influence of the Bi chemical state on the photocatalytic activity was investigated using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and diffused reflectance spectroscopy to study the struc-ture, chemical state and light absorption characteristics, respectively. The photocatalytic activity was evaluated by the H2 evolution water splitting reaction. The monoclinic phase of NaTaO3 re-mained intact for the two Bi-doped samples, but the Ta–O–Ta bond was distorted from 180° after Bi doping. XPS results indicated that Bi3+ was doped into NaTaO3 with the Bi(NO3)3 precursor, while Bi5+ and Bi3+ were doped into NaTaO3 with the NaBiO3 precursor. The two samples showed identical light absorption, where doping with Bi extended the light absorption to long wavelength light as expected. However, Bi3+ doping did not promote the photocatalytic activity of NaTaO3, while Bi5+and Bi3+ doping did. The distorted Ta–O–Ta bond from 180° due to doping with Bi was detrimental for charge carrier transfer in the photocatalytic process. In contrast, the vacancies or defects in the NaTaO3 lattice induced by Bi doping for charge balance were beneficial for charge carrier separa-tion. The opposing action of these two factors resulted in the activity of the Bi3+-doped sample being comparable with pristine NaTaO3. For Bi5+- and Bi3+-doped NaTaO3, a high concentration of defects was induced by the high valence Bi5+ ion and this led to its higher photocatalytic activity. Our results indicated that charge carrier transfer is a priority factor in the photocatalytic process and the dop-ing of a high valence ion in the ABO3 structure is a way to promote the separation of charge carriers.