Accurate structural descriptor enabled screening for nitrogen and oxygen vacancy codoped TiO2 with a large bandgap narrowing. (20th September 2022)

• Record Type: Journal Article
• Authors: Zhang, Kangyu; Yin, Lichang; Liu, Gang; Cheng, Hui-Ming
• Is Part Of: Journal of materials science & technology. Volume 122(2022)
• Page Start: 84
• Page End: 90
• Publication Date: 2022-09-20
• Subjects: Structural descriptor -- TiO2 -- Bandgap narrowing -- Doping -- Machine learning -- Density functional theory; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2021.12.062
• Languages: English
• ISSNs: 1005-0302

Abstract

Highlights: An accurate structural descriptor to represent the doping configurations of N/VO -codoped anatase TiO2 is constructed. Machine learning assisted electronic properties screening for the optimal doping configurations is enabled by the structural descriptor. Two types of doping configurations featured by a linear and corner-sharing TiO5 N1 /TiO4 N2 octahedron chain with a large bandgap narrowing are identified. The spatial ordering of N-dopants has been uncovered as the intrinsic reason for a large bandgap narrowing in N/VO -codoped TiO2 . Abstract: Nitrogen (N) doping has been widely adopted to improve the light absorption of TiO2 . However, the newly introduced N-2 p states are largely localized thus barely overlap with O-2 p states in the valence band of TiO2, resulting in a shoulder-like absorption edge. To realize an apparent overlap between N-2 p and O-2 p states, charge compensation between N 3− and O 2− via electron transfer from oxygen vacancies (VO ) to N dopants is one possible strategy. To verify this, in numerous doping configurations of N/VO -codoped anatase TiO2, we identified two types of VO position independent N-dopant spatial orderings by efficient screening enabled with a newly designed structural descriptor. Compared with others, these two types of the N-dopant spatial orderings are highly beneficial for charge compensation to produce an apparent overlap between N-2 p and O-2 p states, therefore achieving a large bandgap narrowing. Furthermore, the two types of the N-dopant spatial orderings can also be generalized to N/VO -codoped rutile TiO2 for bandgap narrowing.