Upconverting luminescence and surface plasmon resonance synergistically boost photocatalytic activity of LaOCl:Yb3+,Er3+/Bi2MoO6/Ag nanofiber S-scheme heterojunction photocatalyst for degradation of organic contaminants

The widespread applications of photocatalysts are tremendously hindered by the factors such as slow transfer rate and fast recombination of electron-hole pairs, poor light absorption, a limited number of surface active sites and inefficient utilization rate of near-infrared (NIR) light in the solar spectrum. According to the energy band engineering strategy, one-dimensional (1D) LaOCl nanofibers (LOC NFs) with superior charge carriers transfer, Yb ions and Er ions with excellent upconverting (UC) luminescence, two-dimensional (2D) Bi₂MoO₆ (BMO) nanosheets with multiple active sites and zero dimensional (0D) Ag nanoparticles (NPs) with strong conductivity and intensive light absorption are rationally selected. These substances with peculiar traits are orderly assembled into 1D LaOCl:Yb³⁺,Er³⁺/Bi₂MoO₆/Ag nanofibers (LOC:Yb,Er/BMO/Ag NFs) S-scheme heterojunction photocatalyst with 1D/2D/0D hierarchical structure to address the above challenges. Co-doping Yb ions and Er ions into LOC NFs facilitates the conversion of non-available NIR light to available visible light, effectively increasing the utilization rate of NIR light within the solar spectrum and achieving full spectral response to boost photocatalytic activity. 2D BMO nanosheets are loaded on 1D LaOCl:Yb³⁺,Er³⁺ nanofibers (LOC:Yb,Er NFs) to form ample and stable heterojunctions. The surface plasmon resonance (SPR) of 0D Ag nanoparticles (NPs) facilitates the rapid migration of electrons and holes on the surface of LOC:Yb,Er/BMO/Ag NFs to enhance the photocatalytic ability. Benefiting from the above advantages, under simulated sunlight illumination for 60 min, the photocatalytic degradation efficiencies of methylene blue (MB), tetracycline hydrochloride (TCH) and Levofloxacin (LEV) by LOC:Yb,Er/BMO/Ag NFs with hierarchical structure reach 91.52 %, 88.63 % and 89.16 %, respectively. The intermediate products of MB, TCH and LEV degraded photo-catalytically by LOC:Yb,Er/BMO/Ag NFs are detected by using liquid chromatography-mass spectrometry (LC-MS), and a reasonable photocatalytic degradation pathway is elucidated. Further, on the basis of the experimental results of active species detection, a reasonable S-scheme heterojunction transfer mechanism with synergistic enhancement of upconverting luminescence and SPR is proposed. The new findings in this work advance the development of photocatalysts to degrade organic contaminants.