Designing Polychromatic Er3+/Yb3+-Codoped Bi2WO6 Upconverting Nanoparticles with Enhanced Visible-Light-Triggered Photocatalytic Properties toward Tetracycline Degradation.

ABSTRACT

To address the unsatisfactory photodegradation capacities of photocatalysts, Er3+/Yb3+-codoped Bi2WO6 (Bi2WO6Er3+/xYb3+) nanoparticles (NPs) with polychromatic upconversion (UC) emission and boosted visible-light-triggered photocatalytic abilities were designed. First-principles density functional theory was employed to study the impact of Er3+ and Yb3+ codoping on the electronic structure of Bi2WO6. Upon 980 nm excitation, the resultant NPs emitted polychromatic UC emissions caused by energy back transfer from Er3+ to Yb3+. Moreover, the involved UC emission mechanism was clarified through examining the pump power related to UC emission spectra. By investigating the visible-light-induced tetracycline (TC) decomposition, the photocatalytic activities of developed NPs were explored, where Bi2WO6Er3+/0.07Yb3+ NP can degrade 81.76% of TC within 30 min, with a k value of 0.0552 min-1. Both the theoretical calculation and trapping results reveal that the •O2-, h+, and •OH were formed during the pollutant removal process. Additionally, the toxic TC can be photodegraded to nontoxic products via the synthesized photocatalysts, leading to wastewater purification. These achievements manifest that Bi2WO6Er3+/xYb3+ NPs are promising visible-light-triggered photocatalysts to degrade pollutants, and our findings also propose a facile approach to regulate the photocatalytic activities of photocatalysts via utilizing doping and UC emission strategies.