The Study On The Noble Metal Modified Bi₂WO₆ Photocatalytic Degradation Of BPA And Gaseous Toluene

Photocatalytic technology has been used widely for wastewater treatment and air purification due to its completely degradable,clean and renewable features.Titanium dioxide?TiO₂?is the most popular photocatalyst for environmental remediation with abundance,low material cost,and outstanding chemical properties.However,TiO₂ can be only excited by ultraviolet light due to wide band gap,which make it difficult be widely used in reality.Recently,Bi₂WO₆ was widely explored by extensive studies due to its narrow-band-gap,excellent intrinsic physical and chemical properties.However,the photocatalytic performance of pure Bi₂WO₆ is still limited,it is necessary to perform some technologies to improve the photocatalytic activity of Bi₂WO₆.In this paper,oxygen vacancies sufficient Bi-BWO was fabricated via a simple in-situ NaBH₄ reduction method,Bi-BWO performed better photocatalytic activity than Bi₂WO₆.Through synchronized deposition of Pt or Au,the photocatalytic performance was further increased.In addition,Pt/Bi-BWO was used for photocatalytic degradation of gaseous toluene under visible light illumination.The chief research includes the following:Oxygen vacancies sufficient Bi-BWO were prepared using a simple in-situ NaBH₄reduction method with Bi₂WO₆ as precursor.When the molar ratio of Bi₂WO₆ and NaBH₄was 1:0.2,0.2Bi-BWO performed the best visible photocatalytic activity of BPA.The 55.4%of BPA was removed within 2 h,improved clearly 26.1%compared to pure Bi₂WO₆?29.3%?.The oxygen vacanices updated the level of valence band,reduced the band gap.The free radicals quenching experiments indicated that·O₂^-and h⁺were the dominant active species,and·OH played minor role in the photocatalytic process.The generation of oxygen vacancies actived O₂ to produce reactive oxygen species.A novel metal assisted self-modified Bi₂WO₆ composites?Pt/Bi-BWO or Au/Bi-BWO?with high oxygen vacancies concentration was successfully fabricated via a simple in-situ NaBH₄ reduction method in presence of H₂PtCl₆·6H₂O or H₂AuCl₆·4H₂O.The deposition of novel metal increased the photocatalytic performance of Bi-BWO.When the contents of Pt in Pt/Bi-BWO were 0.1%,Pt/Bi-BWO performed the best visible photocatalytic activity and the 84.4%of BPA was removed within 2 h.When the contents of Au in Au/Bi-BWO were 0.15%,Pt/Bi-BWO performed the best visible photocatalytic activity and the 68.9%of BPA was removed within 2 h.The initial pH of BPA would influence the photocatalytic performance of samples,The alkaline environment was in favor of the adsorption of BPA on the surface of samples,resulting in better photocatalytic performance.The mechanism of the promotion would be deduced as following:the generated oxygen vacancies due to the reduction of NaBH₄ were also partly overlapped with valence band?VB?of Bi₂WO₆ to up the VB level,leading to a narrowed band gap,and the deposition of Pt increased the amount of oxygen vacancies.In addition,the Pt and Bi deposited on the surface of Bi₂WO₆ could act as electron traps to suppress the recombination of electrons and holes to improve photocatalytic activity.The Pt/Bi-BWO composites were applied for photocatalytic degradation of VOCs under visible light illumination.The Pt/Bi-BWO performed excellent photocatalytic activity on the degradation of gaseous toluene under visible light illumination.The photocatalytic reaction rate of 0.15%Pt/Bi-BWO was 2.88 times higher than that of Bi₂WO₆.Over 90%gas phase toluene was removed by 0.15%Pt/Bi-BWO within 1.5 h.The Pt/Bi-BWO had also great stability confirmed by circulating runs texts,and over 80%of toluene was mineralized to generate CO₂.The DFT calculations was used to simulated the distribution of oxygen vacancies and Pt on surface of Bi₂WO₆?1 3 1?.The the work function was calculated as 5.416 eV,5.369 eV,5.181 eV for Bi₂WO₆?1 3 1?,Bi₂WO₆?1 3 1?+Ov7,Bi₂WO₆?1 3 1?+Ov7+Pt.The structure of Pt/Bi-BWO contributed to the adsorption of O₂.