Fabrication Of Co/N Co-doped Hollow Carbon Frameworks For Efficient Photocatalytic Degradation Of Gaseous Toluene

In recent years,with the increasingly serious problems of the atmospheric environment,volatile organic pollutants?VOCs?,as the third largest gas pollutants after NO_x and SO_x,have been attracted more and more attention in the world.Because of the toxic effects of VOCs,it has a serious threat to human beings and the ecological environment.Therefore,according to the pollution status of VOCs,a variety of control technologies have become a research hotspot.Compared with the traditional control technology of VOCs,photocatalytic oxidation,as one of the most promising green purification technology,has been widely studied all over the world.Among the traditional photocatalysts,semiconductor photocatalysts are the most widely used.For example,TiO₂ is one of the most widely used and discussed semiconductor photocatalysts,which has the advantages of low cost,non-toxic and good stability.However,there are some disadvantages of TiO₂,such as wide energy gap?3.2 eV?and fast photogeneration rate.Due to the wide energy gap of TiO₂,it can only use ultraviolet light?about 4%of the total solar spectrum?.Therefore,finding a stable and highly active photocatalyst with good visible light response is a key issue to solve the above limiting conditions.The aim of this work is to develop a new visible light induced photocatalyst for the purification and removal of VOCs.The main contents of the study are as follows:?1?Using ZIF-67 and dopamine as precursors,the Co/N co-doped carbon framework nanomaterials with hollow porous structure were successfully synthesized by the polycondensation of dopamine.A series of characterization methods were used to analyze and measure the catalytic materials.The results showed that the synthesized catalyst Co/N-C well retained the rhombic dodecahedron shape of ZIF-67 and had the characteristics of uniform particle size and hollow porous structure.In addition,the catalyst has been successfully doped with Co and N by one-step.The Co,N had formed the Co-N-C active sites with C.The catalyst Co/N-C had high specific surface area and abundant pore structure,which was beneficial to the exposure of more active sites for adsorption and reaction.The light absorption ability of the catalyst was improved.And the wide band gap of the catalyst was small,which indicated that the materials could make full use of visible light.?2?Using toluene as the target pollutants,the photocatalytic activity and mechanism of the catalyst Co/N-C for the degradation process were investigated by in situ FTIR.The results showed that the catalyst Co/N-C had high adsorption ability of gaseous toluene and could reach adsorption equilibrium in a short time.Under visible light irradiation,the photocatalytic degradation efficiency of Co/N-C was the highest,and the conversion rate could reach 78.9%after 6 h.Due to the properties of the catalytic materials,the different reactive oxygen species could be produced after a series of changes in the interface of the catalyst,such as·OH,·OOH,·O₂^-.These free radicals could participate in photocatalytic reactions,so that toluene could gradually convert to benzyl alcohol,benzaldehyde,benzoic acid,and finally mineralized into harmless CO₂ and H₂O.