Investigation Of Photocatalytic Degradation Of Typical Air Pollutants By Defective BiSbO₄ And Its Reaction Mechanism

With the rapid development of economy and industry,air pollution has become a hot topic for people all over the world.VOCs and NO_X,as typical air pollutants,are discharged indiscriminately,which causes a series of environmental problems.In recent years,photocatalytic technology,as an economic and sustainable energy driven green technology,can directly realize the conversion of NO_X and VOCs into non-toxic harmless substances under mild conditions.Therefore,in order to promote the application of photocatalytic oxidation technology in practical industry,the selected photocatalytic materials should not only have high efficiency of photocatalytic performance,but also have the characteristic of stable performance,low cost,cheap and easy preparation.Recently,a series of novel wide band gap p-block metal oxides/hydroxides photocatalysts have shown good performance and stability in the degradation of benzene series.Among them,BiSbO₄ is a potential photocatalyst because of its good degradation activity against organic pollutants.However,due to its wide band gap,the catalyst can only be excited under ultraviolet light,which greatly limits its application.In order to promote the development of BiSbO₄ as a semiconductor photocatalyst,we modify BiSbO₄ material to have highly efficient visible light catalytic performance.With reference to the modification of wideband gap semiconductor photocatalyst,we adopt the method of constructing defect energy level to promote the separation of photo-generated carriers,broaden the optical response range,and achieve excellent visible catalytic performance.However,a common and important problem in the development and application of defective photocatalysts is that the defects are very unstable in the reaction process.However,so far,the mechanism of oxygen defect inactivation in semiconductors and the method of stabilizing the defects have not been revealed.For deactivated and defective photocatalysts,innovative methods should be developed to regenerate catalysts for sustainable photocatalytic applications.We adopt the measure of novel photo-induced defect to introduce oxygen vacancies into BiSbO₄.the formation of oxygen vacancies inhibits the recombination of photo-generated carrier,broadens the light response range,promotes small molecule adsorption activation leading to a large number of active free radicals to participate in the photocatalytic purification NO as confirmed by experiment and density functional theory calculations.These advantages enable BiSbO₄ to have a highly efficient visible light catalytic effect.In addition,oxygen defects are easily filled by oxygen molecules in the air during the reaction process,resulting in reduced defect concentration and deactivation of catalyst.When the deactivated catalyst is re-exposed to ultraviolet light,the photocatalytic efficiency of the catalyst is restored to the original state and the sustainable utilization of oxygen defects is realized.At the same time,the photocatalytic oxidation of NO by BiSbO₄ was elucidated by in situ DRIFT technology,and the reaction path of NO?NO₂?NO₃^-is proposed to efficiently transform NO into non-toxic end products.In the process of photodegradation of VOCs by BiSbO₄under ultraviolet light,oxygen defects are generated in real time,so that oxygen defects can be consumed continuously and replenished in time,so as to achieve defect balance,thereby ensuring the stability of defects,thus ensuring the stability and efficiency of photocatalytic efficiency.According to the gibbs free energy calculated by the DFT,the oxygen vacancies contribute to the spontaneous oxidation of formaldehyde to carbon dioxide.The photocatalytic degradation of toluene and benzene by BiSbO₄ was investigated by in situ DRIFT,GC-MS and DFT calculations.According to the experimental and theoretical results,toluene is more inclined to oxidize to benzyl alcohol,then to benzaldehyde and finally to open the ring.In the process of degradation of benzene,the benzene ring is first activated by holes or other oxidizing species,and then when attacked by hydroxyl radicals opens up to chain acids or long-chain aldehydes,and finally these long-chain carbon compounds are cracked into carbon dioxide.The photo-induced oxygen defect generation and regeneration method proposed in this paper can also be extended to other semiconductor photocatalysts,which provides a new idea for the sustainable development of photocatalysis.In addition,the reaction mechanism of photocatalytic oxidation of VOCs proposed in this paper also provides a new reference for future research.