Zhu Xiaoxia, Luo Xukai, Yuan Hongkuan, Chen Hong, Tian Chunling
School of Physical Science and Technology, Southwest University Chongqing 400715 China
RSC Adv. 2018 Jan 17;8(6):3304-3311. doi: 10.1039/c7ra12058c. eCollection 2018 Jan 12.
SnS nanosheets with three atom thickness have previously been synthesized and it has been shown that visible light absorption and hydrogen evolution through photocatalytic water splitting are restricted. In the present study, we have systematically investigated the electronic structures of anionic monodoped (N and P) and codoped (N-N, N-P, and P-P) SnS nanosheets for the design of efficient water redox photocatalysts by adopting first principles calculations with the hybrid HSE06 functional. The results show that the defect formation energies of both the anionic monodoped and all the codoped systems decrease monotonically with the decrease of the chemical potential of S. The P-P codoped SnS nanosheets are not only more favorable than other codoped systems under an S-poor condition, but they also reduce the band gap without introducing unoccupied impurity states above the Fermi level. Interestingly, although the P-P(ii) codoped system gives a band gap reduction, this system is only suitable for oxygen production and not for hydrogen evolution, which indicates that it may serve as a Z-scheme photocatalyst for water splitting. The P-P(i) codoped system may be a potential candidate for photocatalytic water splitting to generate hydrogen because of the appropriate band gap and band edge positions, which overcome the disadvantage that the pure SnS nanosheet is not beneficial for hydrogen production. More importantly, the result of optical absorption spectral analysis shows that the P-P(i) codoped SnS nanosheet absorbs a longer wavelength of the visible light spectrum as compared to the pristine SnS nanosheet. The P-P(I) codoped system with a lower doping concentration also has an absorption shift towards the visible light region.
此前已合成出具有三个原子厚度的硫化亚锡（SnS）纳米片，并且研究表明，其通过光催化水分解产生的可见光吸收和析氢受到限制。在本研究中，我们采用含杂化HSE06泛函的第一性原理计算方法，系统地研究了阴离子单掺杂（N和P）以及共掺杂（N-N、N-P和P-P）的SnS纳米片的电子结构，以设计高效的水氧化还原光催化剂。结果表明，随着硫（S）化学势的降低，阴离子单掺杂体系和所有共掺杂体系的缺陷形成能均单调下降。P-P共掺杂的SnS纳米片不仅在硫贫化条件下比其他共掺杂体系更有利，而且在不引入高于费米能级的未占据杂质态的情况下降低了带隙。有趣的是，尽管P-P(ii)共掺杂体系实现了带隙减小，但该体系仅适用于析氧而不适用于析氢，这表明它可能作为水分解的Z型光催化剂。由于具有合适的带隙和带边位置，P-P(i)共掺杂体系可能是光催化水分解制氢的潜在候选材料，克服了纯SnS纳米片不利于产氢的缺点。更重要的是，光吸收光谱分析结果表明，与原始SnS纳米片相比，P-P(i)共掺杂的SnS纳米片吸收的可见光谱波长更长。掺杂浓度较低的P-P(I)共掺杂体系也有向可见光区域的吸收位移。
