Visible–near-Infrared Light-Driven Photocatalytic Characteristics of Er3+/Yb3+-Codoped BiOBr Upconverting Microparticles for Tetracycline Degradation

To settle the unsatisfying efficiency and insufficient light harvesting ability of photocatalysts, we report on the development of Er³⁺/Yb³⁺-codoped BiOBr (BiOBr:Er³⁺/xYb³⁺) microparticles that were synthesized by a rational high-temperature solid-state reaction method. The prepared microcrystals exhibit high visible upconversion (UC) emissions with maximum intensities at x = 0.01 when excited by a 980 nm laser. Remarkably, the corresponding UC emission process is attributed to a two-photon absorption route. Furthermore, the photocatalytic activities of as-synthesized compounds were further evaluated through analyzing the visible-near-infrared light-triggered tetracycline degradation. Compared with BiOBr:Er³⁺ microparticles, BiOBr:Er³⁺/xYb³⁺ microparticles present superior photocatalytic properties and the optimal status is achieved when x = 0.05, in which h⁺, ·O₂^-, and ·OH active species contribute to the photocatalytic mechanism. Additionally, the designed microparticles exhibit better photocatalytic abilities than previously reported photocatalysts (i.e., TiO₂, SnO₂) upon full-spectrum light irradiation. These results reveal that Yb³⁺ codoping is able to not only enhance the UC emission properties of BiOBr:Er³⁺ microparticles but also reinforce their photocatalytic activities. Our findings may put forward a facile strategy to regulate the photodegradation capacity of photcatalysts.