A novel synergy of Er3+/Fe3+ co-doped porous Bi5O7I microspheres with enhanced photocatalytic activity under visible-light irradiation

Uniform porous Bi5O7I (BOI) microspheres photocatalysts co-doped with Fe3+ and Er3+ were synthesized by a solvothermal-thermal decomposition method, in which Er3+ with upconversion properties could transform infrared light beyond the absorption edge of Bi5O7I into visible light, and also activate the Fe3+-doped Bi5O7I (Fe-BOI). The photocatalytic activities of the photocatalysts were evaluated by the degradation of three typical colorless model pollutants, i.e., phenol, bisphenol A (BPA), and chloramphenicol (CAP), under visible light irradiation (800 nm > λ > 400 nm). The results showed that the photocatalytic activity of Fe3+/Er3+ co-doped Bi5O7I (Er/Fe-BOI) was much higher than that of the undoped, Fe3+-doped and Er3+-doped Bi5O7I photocatalysts. In addition, Fe3+/Er3+ co-doped Bi5O7I exhibited photocatalytic activity under a 3W LED lamp (red light, λ = 630 nm) with the wavelength beyond the absorption edge of Bi5O7I, which further testified that the upconversion effect of Er3+ generates the enhanced photocatalytic activity of Bi5O7I. Photodegradation mechanism was systematically studied by using various radical quenchers and it was revealed that photogenerated holes (h+) and superoxide radicals (O2−) actively participated, whereas hydroxyl (OH) radicals had negligible contribution in photodegradation of phenol.