Synergistic photocatalytic NO removal of oxygen vacancies and metallic bismuth on Bi₁₂TiO₂₀ nanofibers under visible light irradiation

Tailoring the semiconductors with non-precious metals or defects have been demonstrated to be a fascinating and prospective approach for environmental remediation. In this work, Bi metal and oxygen vacancies (OVs) co-modified Bi₁₂TiO₂₀ nanofibers (Bi/BTO) photocatalysts were synthesized through electrospinning technique and subsequent chemical reduction method for the first time. The Bi/BTO composite photocatalysts exhibit significantly higher photocatalytic NO removal activity than that of pristine BTO under visible light irradiation. The improvement of photocatalytic performance is ascribed to the integrative effect of OVs and surface plasmon resonance (SPR) effect of Bi particles. The presence of OVs is confirmed by X-ray photoelectron spectroscopy and electron paramagnetic resonance spectroscopy. The density functional theory (DFT) calculations reveal that the OVs in BTO induce the formation of a defect level, which is beneficial to increase light absorption. In addition, Bi can act as an electron sink, boosting the separation of photoinduced electron-hole pairs. The trapping experiment and electron spin resonance spectra indicate that the main active species are ·O₂⁻ and h⁺. Moreover, the reaction process over 3% Bi/BTO is monitored by in situ infrared spectroscopy (in situ FTIR) and a reasonable photocatalytic mechanism of NO removal on Bi/BTO is proposed through a combination of experimental and theoretical results.