Application Of Boron-Containing Conjugated Organic Polymers In Photocatalytic Hydrogen Production And Lithium Ion Batteries

The excessive use of fossil fuels has caused environmental pollution and energy shortages.Therefore,research on green energy that can replace fossil fuels has become a current research hotspot.In recent years,hydrogen energy and lithium-ion batteries are the new green energy with the most potential and application prospects,and their research is of great value.The generation of hydrogen energy can be obtained by photocatalytically decomposing water,which is one of the commonly used effective means.The photocatalyst is the core of photocatalytic cracking of water to produce hydrogen.Lithium ion batteries are also receiving much attention as energy storage materials,and electrode materials are one of the key components of battery performance.Organic materials are better than inorganic materials due to their controllable structure,environmental friendliness,and low production cost.They have been widely used in these two types of research.Due to the electron-deficient nature of boron atoms,it can effectively reduce the HOMO-LUMO energy level of the material and improve the electron mobility,etc.,making boron-containing materials have the potential to become high-quality photocatalysts and electrode materials.Therefore,this paper introduces boron into the polymer,synthesizes a series of side-substituted boron-based linear conjugated organic polymers through Sonogashira coupling,and uses them to explore in the field of photocatalytic water splitting and lithium ion batteries,the research content of this paper is as follows:The first chapter:A brief overview of green energy.The second chapter:Using boron monomer M1 as the basic unit,and2,5-diiodothiophene,5,5'-diiodo-2,2'-bithiophene,5,5''-diiodo-2,2':5',2''-trithiophene,2,5-dibromothieno[3,2-B]thiophene,3,6-dibromothieno[3,2-B]thiophene and 4,7-Dibromo-2,1,3-benzothiadiazole was synthesized by Sonogashira coupling to obtain five D-A type linear conjugated polymers PBT1,PBT2,PBT3,PBTT1,and PBTT2,and one A-A type linear conjugated polymer of PBBT.The successful preparation of the materials was confirmed by NMR,solid ¹¹B CP/MAS NMR,FTIR and GPC.The third chapter:Under the simulated visible light of??420 nm,the photocatalytic water splitting hydrogen production performance of boron-containing polymers was studied.The hydrogen production test shows that PBT1,PBT2,PBT3,PBTT1,PBTT2,and PBBT can all produce hydrogen by photocatalytic water splitting,and their hydrogen production rates are 53?mol g^-11 h^-1,833?mol g^-1 h^-1,541?mol g^-1h^-1,212?mol g^-11 h^-1,70?mol g^-1 h^-11 and 61?mol g^-1 h^-1 respectively,this may be due to the introduction of electron-deficient boron-containing units?A?that can adjust the band gap of the polymer.From the analysis of hydrogen production results,the linear D-A type conjugated polymer has higher hydrogen production activity than the linear A-A type conjugated polymer?PBBT?,which is due to the intramolecular charge transfer interaction between the donor?D?and acceptor?A?units,resulting in narrowing of the band gap and adjustment of molecular energy levels,which indicates that the organic catalyst that is completely acceptor is not an ideal photocatalyst.From the result of the hydrogen production of PBT1,PBT2 and PBT3,the content of thiophene will affect the hydrogen production activity of the catalyst.Compared with PBTT1 and PBTT2,the content of thiophene is the same,the connection position is different,but the hydrogen production activity is very different,which shows that the hydrogen production activity of the catalyst is related to the geometry of the material,which leads to the difference in photocatalytic activity.Compared with PBTT1,PBT2 shows that the spatial structure of the material also has a certain influence on the activity of hydrogen production.The fourth chapter:Using boron-containing polymers PBT1 and PBT2 as anode electrode materials,lithium metal as the counter electrode are assembled into a lithium ion battery,and electrochemical and charge and discharge tests were carried out.The results show that PBT1 and PBT2 have stable rate performance and long cycle performance.When the current density is 1A g^-1,the first discharge specific capacity of PBT1 and PBT2 reaches 375 mAh g^-1.During the charging and discharging process,due to the activation of the material,the capacity increases.Therefore,the specific capacity of PBT1 reaches 252 mAh g^-1 at the highest,and the specific capacity of PBT2reaches 213 mAh g^-1 at the highest.After 10,000 cycles,the specific capacity of PBT1is stabilized at 120 mAh g^-1,the specific capacity of PBT2 is stabilized at 95 mAh g^-1.The fifth chapter:Summary and outlook of this article.