Highly efficient visible/NIR photocatalytic activity and mechanism of Yb3+/Er3+ co-doped Bi4O5I2 up-conversion photocatalyst

Bi4O5I2 has attracted much attention as a visible-light-driven photocatalyst, but its photocatalytic activity should be further improved for future practical application. Herein, we design and prepared Er3+/Yb3+ co-doped Bi4O5I2 nanosheets by a facile solvothermal method. The samples were characterized by XRD, SEM, TEM, XPS, DRS, PL, and EIS. The photocatalytic activities of samples were evaluated by the degradation of RhB and imidacloprid. Among these doped samples, the Bi4O5I2: Er1%,Yb2% exhibits the highest degradation efficiency for RhB and IM under the irradiation of visible or near infrared (NIR) light irradiation. This can be attributed to the up-conversion transition of Er3+, which can convert NIR light beyond the absorption edge of Bi4O5I2 into visible/UV light to excite Bi4O5I2. In addition, the decreased band gap and improved separation efficiency of e−–h+ pairs due to the rare-earth ions as electron traps play roles in the enhanced vis/NIR photoactivity. The h+ and •O2– are the main active species for the degradation of organic pollutants. Based on the experimental results, a plausible mechanism was proposed.