Synthetic And Modification Of G-C3N5 Catalyst And Its Photocatalytic Performance

Fossil energy is a non-renewable resource,and with its large-scale use,it brings a series of problems such as environmental pollution and energy shortage.The photocatalytic activities of carbon nitride material g-C₃N₅,Fe doped g-C₃N₅ and Cu doped g-C₃N₅ nanocatalysts and metal material Ti O₂（see the appendix）were investigated by photocatalytic degradation of organic pollutants（methylene（MB）,methyl（MO）and salicylic acid（SA））and ligin model compounds（2-phenoxy-1-phenylethanol,ppol）under mild conditions.The morphology,structure,specific surface area and elemental content of the composites were characterized using various techniques such as XRD,FT-IR,XPS,TEM,BET,UV-Vis DRS and electrochemistry.The main work includes the following three parts:1.Two kinds of ferric iron and g-C₃N₅hybrid composite were synthesized through post oxidation（Fe/CN-a）and solvothermal（Fe/CN-b）methods.The photo-Fenton catalytic activities of the composites were evaluated by the degradation of MB and MO in a visible light/H₂O₂ system.The results revealed that the iron element exists in the form of monodispersed Fe（ⅠⅠⅠ）in Fe/CN-a,while it formsα-Fe₂O₃ nanocubes in Fe/CN-b.The photo-Fenton catalytic activities are remarkably increased for the ferric iron loaded catalysts.The Fe/CN-b has the highest activity in degrading MB,which increases to 4.8 times as compared with the g-C₃N₅.While the Fe/CN-a has the highest activity in degrading MO,which increases by 17.0 times compared to the g-C₃N₅.The Z-scheme heterojunction,growth of visible light absorption and efficient electron-hole separation account for the photo-Fenton catalytic activity enhancement.The characterization results of XRD,TEM and XPS showed that Fe/CN-b successfully formed a Z-scheme heterojunction structure by solvothermal method,which enhanced the visible light absorption range and effective separation of electron-hole,thus enhancing the photo-Fenton catalysis.2.The synthesis of g-C₃N₅（CN-2）using porous silica as a template agent,and Cu-based g-C₃N₅ composite catalysts were synthesized through hydrothermal（Cu O/CN）and impregnation（Cu₂O/CN）methods.The photocatalytic redox depolymerization reaction of lignin model compounds was carried out under visible light/H₂O₂ system.Both Cu O/CN and Cu₂O/CN catalysts showed good photocatalytic redox activity for lignin depolymerization,with 85.95%conversion of ppol at room temperature and 35.78 and 48.94%yields of the target products phenol and acetophenone,respectively.The yields of phenol and acetophenone,the target products formed by Cu₂O/CN photocatalytic ppol,reached 35.78 and 48.94%,respectively.The radical capture experiments revealed that the main active species of Cu O/CN in photocatalytic depolymerization of ppol was·O₂^-,while the main active species of Cu₂O/CN in photocatalytic depolymerization of ppol was h⁺.3.The anatase Ti O₂ nanoparticles were successfully prepared by hydrothermal and roasting methods using titanium ammonium oxalate monohydrate as the only reactant.The activity of the catalysts was evaluated by performing photocatalytic degradation experiments of MB and SA under UV light.It was found that the photocatalytic activity of Ti O₂-550 was the highest,and its catalytic efficiency increased 8.4 times and 2.8 times compared to Ti O₂-700 and Ti O₂-c for MB degradation,and 4.5 times and 2.3 times compared to Ti O₂-700 and Ti O₂-p for SA degradation.The results show that the photocatalytic performance of Ti O₂ and its morphology and structure have great influence.Ti O₂-550 has a bead-like structure,which exhibits higher crystallinity and purer anatase phase with the specific surface area of 37.2m²·g^-1 and the pore size of 23.9 nm,showing a high photocatalytic efficiency.