Improvement Of The Photocatalytic NOx Removal Performance With Bismuth Oxyhalide

The consumption of fossil fuels and industrial exhaust emissions have led to increasing air pollution problems.As one of the industrial waste gases,nitrogen oxides are harmful to human health directly or indirectly and received much attention recently.Photocatalysis has certain advantages in the removal of low-concentration gaseous nitrogen oxides due to its simple operation,low cost,and high efficiency.TiO2 semiconductor photocatalyst is one of the earliest-discovered photocatalysts,which has been widely used.However,TiO2 has a large bandgap and a low photocatalytic efficiency.Bismuth oxyhalide(BiOX)photocatalyst,which possesses layered structures and unique photoelectric properties,has drawn more attention.But BiOX photocatalysts still have some problems,such as low photocatalytic efficiency,poor product selectivity,and difficult in direct application of powder catalysts.At present,the photocatalytic performance of BiOX is generally lower than 50%,so it can be significantly improved.In addition,the photocatalytic removal of nitrogen oxides by BiOX has a poor selectivity,in addition to nitrate,a large amount of toxic by-products such as NO2 was generated.Besides,in the photocatalytic removal of nitrogen oxides,powder catalysts would be easily dispersed and lost by the wind and difficult to recover.1.Aiming for improving the visible photocatalytic performance and product selectivity of BiOX,we prepared BiOBr containing oxygen vacancies and Bi nanoparticles by one-step solvothermal method.Density functional theory calculations showed that Bi's load and oxygen vacancies introduced new band between the conduction band and valence band of BiOBr,thereby the bandgap of BiOBr was reduced which may improve the visible photocatalytic performance of BiOBr directly.Meanwhile,Bi loading and oxygen vacancies provided new paths for electrons transfer.Photocatalytic nitrogen oxides removal experiments showed that the presence of Bi and oxygen vacancies significantly improved the BiOBr photocatalytic performance from 43%to 70%and the amount of by-product was greatly reduced.EPR and NO-TPD test results showed that oxygen vacancies on the surface of BiOBr promoted the separation of photocatalytic products.DRS and photocurrent test showed that Bi loading can effectively enhance the response of BiOBr in the visible region,improved the separation efficiency of photogenerated carriers,which is consistent with the result of theory calculation.Therefore,the presence of Bi loading and oxygen vacancies can effectively improve the photocatalytic performance and the selectivity of BiOBr.2.For the photocatalytic removal of NO by powdered catalysts,there are problems such as being easily dispersed by the wind and difficult to recover.To solve these problems,we used the in-situ loading method to load BiOCl on the surface of glass fiber cloth.The results of photocatalytic of NO confirmed that we completed the immobilization of the catalyst successfully and the activity of visible light catalytic removal of NO could increase to 68%with the resulting photocatalytic component.Then,we explored the load process and optimized the load conditions of the BiOCl component.In order to test the effect of the prepared BiOCl component in practical applications,we used air purifier as a test platform to detect the ability of NO degradation with the BiOCl component.The experimental results showed that the components have a potential catalytic activity in practical applications.After the addition of the component,the removal rate of NO by air purifier was significantly increased from 41.9%to 72.8%.