Study On The Photocatalytic Properties Of Capping Ligand Modulation Of CdS Quantum Dots And Triazine Graphdiyne

The development of industry and human activities consume a large amount of non-renewable resources,causing a series of problems such as energy depletion and greenhouse effect.In order to solve the energy crisis and mitigate the greenhouse effect,a sustainable development strategy is needed.Therefore,the CO₂ recycling and the development of new energy sources have received extensive attention from all walks of life.In many technologies of CO₂ conversion and hydrogen production,photocatalysis technology has been favored by many researchers because of its simple process and low cost.Hence,the construction of a photocatalysis system with high selectivity,high activity and high conversion rate is a key issue for CO₂ conversion and hydrogen production.At present,the development of photocatalysis system still faces some problems that need to be solved urgently.For example,the poor selectivity of photocatalytic product,the insufficient stability of the photocatalyst,the existence of noble metal in efficient photocatalytic system,and the serious recombination of photogenerated carrier.In view of the above key scientific issues,this thesis focuses on the surface modification of catalysts and the preparation of new organic semiconductors,and applied them to photocatalytic reduction of CO₂ and hydrogen production.The main research contents and conclusions are as follows:（1）The effect of quantum dot surface capping ligands on the performance of photocatalytic CO₂ reduction was systematically studied by using CdS quantum dots（QDs）as a photocatalyst.Compared to the surface ligands with alkyl chains,photophysical and electrophysical studies have shown that the conjugated ligands are more conducive to the separation of photogenerated carriers in CdS quantum dots,resulting in an improved performance of photocatalytic CO₂ reduction.Among them,when mercaptopyridine containing N element was used as capping ligand,experimental and theoretical studies have shown that the N atom in the mercaptopyridine is favorable for the adsorption of CO₂ and can act as an active site for photocatalytic CO₂ reduction.Therefore,CdS quantum dots with mercaptopyridine as the capping ligand show the best photocatalytic CO₂ reduction performance.The selectivity,yield,and TON of CO product reach up to 96%,244.60 μmol,and 48920,respectively.（2）We have synthesized a 2,4,6-triethynyl-tetraphenyl-1,3,5-triazine segment,and employed it as the monomer to exploit a new triazinyl graphdiyne（PTEPT）with in situ doped nitrogen by the Glaser-Hay coupling reaction,which enriches the members of the graphdiyne family.Absorption spectrum and electrochemical measurements have disclosed that PTEPT has good light absorption in the visible light region,and its band structure satisfies the thermodynamics requirements for photocatalytic hydrogen production.Further experimental researches have shown that PTEPT is an excellent photocatalytic catalyst for hydrogen production,and the yield of hydrogen production can reach 9665 μmol/g.