Enhancement of solar-driven photocatalytic activity of oxygen vacancy-rich Bi/BiOBr/Sr2LaF7:Yb3+,Er3+ composites through synergetic strategy of upconversion function and plasmonic effect

Abstract

For better use of solar energy, the development of efficient broadband photocatalyst has attracted extraordinary attention. In this study, a ternary composite consisting of Sr₂LaF₇:Yb³⁺,Er³⁺ upconversion (UC) nanocrystals and Bi nanoparticles loaded BiOBr nanosheets with oxygen vacancies (OVs, SLFBB) was designed and synthesized by multistep solvent-thermal method. Mechanisms of in-situ formation of Bi nanoparticles and OVs in BiOBr/Sr₂LaF₇:Yb³⁺,Er³⁺ composites (SFLB) are clarified. The Bi metal and OVs enhanced the light-harvesting capacity in the region of visible-near-infrared (Vis-NIR), and promoted the separation of electron-hole (e^-/h⁺) pairs. Furthermore, the surface plasmon resonance (SPR) effect of Bi metal can improve the energy transfer from Sr₂LaF₇:Yb³⁺,Er³⁺ to BiOBr via nonradiative energy transfer process, resulting in enhancing the light utilization from upconverting NIR into Vis light. Due to the synergistic effects of UC function, SPR and OVs, the SFLBB exhibited obviously enhanced photocatalytic ability for the degradation of BPA with a rate of 8.9 × 10^-3 min^-1, which is about 2.78 times higher than 3.2 × 10^-3 min^-1 of BiOBr (BOB) under UV-Vis-NIR light irradiation. This work provides a novel strategy for the project of high-efficiency Bismuth-based broadband photocatalysts, which is helpful to further understand the mechanism of enhanced photocatalysis by UC function and plasmonic effect.

Keywords: Bi metal; BiOBr/Sr(2)LaF(7):Yb(3+),Er(3+) composites; Broadband photocatalysis; In-situ generation; Oxygen vacancies.