Polyoxometalates-doped Bi₂O₃₋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 PW₁₂O₄₀³⁻-doped Bi₂O₃₋ₓ/Bi Schottky photocatalysts PW₁₂@ Bi₂O₃₋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 Bi₂O₃₋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@ Bi₂O₃₋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.

四溴雙酚A（TBBPA）是一種重要的塑膠添加劑和阻燃劑，廣泛用於樹脂、塑膠、膠黏劑以及塗料中。它不僅是持久性的機污染物，還是一種內分泌干擾物，具有免疫毒性、神經毒性和細胞毒性。NOx，特別是NO，是主要的大氣污染物之一，是形成PM2.5的重要前體，也容易引起酸雨，引發光化學煙霧、臭氧損耗、溫室效應等，嚴重危害生態環境和人類健康。光催化技術乙太陽能為驅動力，被認為是高效去除各種環境污染物的有效策略之一。但目前報道的光催化劑，大多僅適用於特定條件下單一污染物的高活性去除，嚴重限制了其發展，難以滿足日益復雜的多功能環境凈化需求。因此,設計廉價、高效、穩定的廣譜光催化劑對拓展光催化的應用具有重要意義。廉價的鉍基半導體光催化劑具有良好的可見光吸收能力，被認為是有前景的高效可見光催化劑之一。其中， Bi₂O₃作為組成最簡單的鉍基光催化劑，因其無毒、可見光催化活性好、穩定性好而備受關注。同時，其價帶是由O2p以及Bi6s軌道雜化而成，有利於光生載流子在體相中的遷移，增強導電性。但Bi₂O₃在實際應用中仍面臨著氧化還原活性不足和光生載流子分離效率低等問題，限制了其應用。因此，對Bi₂O₃進行修飾和調控，以增強其光催化活性，拓展其應用範圍,成為推動Bi₂O₃光催化劑實用化的關鍵和挑戰。本文通過簡單的靜電紡絲/煆燒/原位NaBH₄還原方法，制備了一系列多陰離子[PW₁₂O₄₀]³⁻(PW₁₂)摻雜的Bi₂O₃₋ₓ/Bi光催化劑PW₁₂@ Bi₂O₃₋ₓ/Bi-n（PBOB-n，其中n為NaBH₄的用量，n=6, 12, 18, 24和48 mg）.在該復合光催化劑中， PW₁₂的摻雜可以有效地調節Bi₂O₃₋ₓ的電子結構，並改善其氧化還原性能。同時， PW₁₂作為電子淺阱，還可以促進光生載流子的分離。此外，金屬Bi納米粒子與PW₁₂@Bi₂O₃₋ₓ之間良好的肖特基結進一步加速了光生載流子的分離。這些因素的協同作用使PBOB-n表現出良好的光催化活性，其中，PBOB-18光催化活性最好，在可見光照射下催化TBBPA降解率達93.7%，較Bi₂O₃活性高4.4倍。此外，PBOB-18表現出較高的光催化去除NO活性，在30 min內去除率達到83.3%，是目前活性較高的Bi基光催化劑之一。本文還結合實驗結果提出了PBOB-18高效光催化去除TBBPA和NO的可能機理。綜上，本文為低成本、高效、穩定和多功能光催化劑的設計提供了一定參考。 Copyright © 2022 Dalian Institute of Chemical Physics, the Chinese Academy of Sciences.