Study On Defect And Surface Modification To Improve The Photocatalytic Activity Of Bismuth Oxycarbonate And Carbon Nitride

Bismuth oxycarbonate is the main component of bismutite and a kind of environmentally friendly photocatalytic material.Due to the large forbidden band width,it cannot absorb visible light which means a low solar energy utilization rate.Because of the abundant oxygen atoms in its crystal structure,in this thesis,we constructed oxygen vacancy structure defect to increase visible light absorption and improves photocatalytic activity.Compared with bismuth oxycarbonate,polymer carbon nitride has good visible light absorption,good chemical stability and low preparation cost.However,low photo-generated carriers separation efficiency and other problems limit the practical application of polymer carbon nitride.In this thesis,defect structure construction strategy and surface modification strategy are adopted to improve the photo-generated carrier separation efficiency and substrate activation under the condition of retaining excellent visible light absorption of carbon nitride.Meanwhile,polymer carbon nitride powder was also cured into a porous film to explore its role in practical photocatalytic applications.The specific research content is as follows:?1?Bismuth oxycarbonate with concentration adjustable oxygen vacancy was prepared by a hydrolytic co-precipitation method at room temperature.Oxygen vacancy defect was found in[Bi₂O₂]²⁺layer and CO₃^2-anion.Oxygen vacancy defect created a defect level in the band structure of bismuth oxycarbonate and increased photo-generated carriers separation efficiency which improving the photocatalytic hydrogen production,nitric oxide degradation and tetracycline hydrochloride degradation activity.?2?In order to improve the photocatalytic activity of polymer carbon nitride,the defect structure construction strategy was utilized again.The heptazine ring structure defect in the layer of polymer carbon nitride was constructed to improve injection electron lifetime,photo-generated carriers'separation and migration efficiency without affecting the excellent light absorption of polymer carbon nitride.?3?Surface hydroxyl modification was applied to polymer carbon nitride to improve the photocatalytic hydrogen production activity.Surface hydroxyl modification does not affect the specific surface area,band structure and other physical properties,but can change the surface local charge distribution,increase the photo-generated carriers'separation,promote the adsorption and activation of protons.The apparent quantum efficiency of photocatalytic hydrogen production was 9.1%??<420 nm?.?4?In order to improve the photocatalytic carbon dioxide reduction ability of polymer carbon nitride,the surface modification strategy was utilized again.Gold sites was modified on the surface of carbon nitride to greatly improve the efficiency of carbon dioxide reduction to produce carbon monoxide which reached 0.991?mol/h?50 mg sample?.?5?The surface hydroxyl-modified rod-shaped polymer carbon nitride and PVDF-HFP were cured into a photocatalytic porous film which can solves the secondary pollution problem of powder polymer carbon nitride.The photocatalytic porous film has good photocatalytic activity of hydrogen production,MO degradation and sterilization.