Ionothermal Synthesis Of Heteroatom Modified Carbon Nitride And Its Photocatalysts Hydrogen Evolution For Water

With the development of society,the energy shortage has severely restricted the sustainable development of the economy and society.Therefore,it is extremely urgent to vigorously develop renewable and clean energy.Semiconductor photocatalysis technology can use solar photolysis to produce hydrogen,and convert low-density solar energy into high-density chemical energy,which is one of the effective ways to solve energy problems.Non-metallic graphite phase carbon nitride（g-C₃N₄）semiconductor is widely used in the field of photocatalysis due to its unique photoelectric properties,suitable band gap and excellent chemical stability.Non-metallic graphite phase carbon nitride（g-C₃N₄）semiconductors are widely used in the field of photocatalysis due to their unique photoelectric properties,suitable band gap and excellent chemical stability.It has important scientific research value in the photocatalysts hydrogen evolution for water splitting.However,its lower specific surface area and higher carrier recombination rate severely limit its photocatalytic activity.By performing element doping,morphology control and microstructure optimization on g-C₃N₄,the molecular and electronic structures can be optimized,the utilization of solar energy can be improved,and the photocatalytic efficiency can be improved.In this paper,g-C₃N₄ was used as the research object,and the chemical composition and micro-polymerization structure of ionic liquid in-situ non-metal doping and molten salt ionothermal post-treatment were optimized to improve the photocatalytic performance of the material.Focusing on these two modification methods,the main research contents and results of this thesis are as follows:（1）In-situ non-metallic element doping of ionic liquid:Iodized ionic liquid is used as the doping source.The C/I co-doping modification of g-C₃N₄promotes the charge transport performance through elemental composition,microstructure adjustment,and optical properties,thereby improving the hydrogen production performance of photocatalysts water splitting.（2）Thermal post-treatment of molten salt ions:post-heat treatment of C/I co-doped g-C₃N₄ by molten salt ion thermal method to obtain crystalline g-C₃N₄,the visible light absorption intensity and polymerization degree are improved,and the photocatalytic production of H₂ is remarkably promoted.（3）The C/I co-doped g-C₃N₄was subjected to molten salt ion thermal post treatment in an inert atmosphere.The inert gas atmosphere is used to suppress the decomposition process,further optimize the conjugate structure,and at the same time regulate the microstructure of the material,increase the specific surface area and homogenize the pore structure.The molten salt ionothermal treatment in the N₂ atmosphere further improves the photocatalytic hydrogen evolution performance.The innovations of this paper are as follows:（1）Porous C/I co-doped carbonized nitrogen materials were successfully synthesized by in-situ doping with iodized ionic liquids.（2）The ionic liquid in-situ doping and molten salt ionothermal method are effectively combined to optimize the polymerization degree of the doped CN,and a partially crystalline CN is obtained.（3）Thermal post-treatment of molten salt ions under inert gas to prepare high-polymerization doped g-C₃N₄ nanosheets with large specific surface area.Significantly increase the surface active site of the catalyst,promote the transport of photogenerated carriers,and improve the H₂ efficiency of photocatalysis.