Polyoxometalates-doped Bi₂O_3–x/Bi photocatalyst for highly efficient visible-light photodegradation of tetrabromobisphenol A and removal of NO

Bismuth-based photocatalysts are a class of excellent visible-light photocatalysts; however, their redox activity is relatively poor and the efficiency of photogenerated carrier separation is low, limiting their development and application in the field of photocatalysis. To address these issues, a series of polyoxometalate PW₁₂O₄₀^3–-doped Bi₂O_3–x/Bi Schottky photocatalysts PW₁₂@Bi₂O_3–x/Bi-n (PBOB-n, where n is the amount of NaBH₄, i.e., 6, 12, 18, 24, and 48 mg) were prepared by a simple electrospinning/calcination/in-situ NaBH₄ reduction method. In this composite photocatalyst, the doping of PW₁₂ could effectively adjust the electronic structure of Bi₂O_3–x and improve its redox properties. As a shallow electron trap, PW₁₂ promoted the separation of the photogenerated carriers. Furthermore, desirable Schottky junction between the metal Bi nanoparticles and PW₁₂@Bi₂O_3–x further accelerated the separation of the photogenerated carriers. The synergistic effect of the aforementioned factors endowed PBOB-n with excellent photocatalytic activity. Among the samples, PBOB-18 exhibited superior photocatalytic activity. Under visible-light irradiation, 93.7% (20 mg catalyst) of 20 ppm tetrabromobisphenol A (TBBPA, 20 mL) was degraded in 60 min. Its activity was 4.4 times higher than that of Bi₂O₃. PBOB-18 also exhibited an ultrahigh photocatalytic performance for the removal of NO. Its removal rate (600 ppb) reached 83.3% in 30 min, making it one of the most active Bi-based photocatalysts. Furthermore, the photocatalytic mechanisms of PBOB-18 for TBBPA and NO have been proposed. This work provides a new direction and reference for the design of low-cost, efficient, stable, and versatile photocatalysts.