Design And Preparation Of Layered Nanosheet Array Photocatalytic Materials And Research On Visible Light-driven Synthesis Of Ammonia

Due to the indispensability of nitrogen fertilizers in the world’s chemical industry and agriculture,the development of synthetic ammonia technology is an important cornerstone to promote the progress of human society.So far,scientists are still exploring more advanced ammonia synthesis technology,hoping to find a route to convert inert nitrogen molecules into ammonia at lower temperatures and pressures to replace the traditional Haber-Bosch process.Among them,the use of clean light energy to drive the room temperature activation of nitrogen molecules provides a new idea for the realization of ammonia synthesis under green conditions.The key scientific issue is how to design and prepare semiconductor photocatalytic materials with high activity and broad spectral response so that they can effectively adsorb,activate and reduce nitrogen molecules.Currently,a variety of photocatalytic materials for nitrogen fixation have been reported.As one of the most common semiconductor photocatalysts,Ti O₂has attracted widespread attention due to its stable chemical properties,low cost and easy availability,and low toxicity.However,Ti O₂has a wide band gap,short carrier migration distance and lack of effective activation sites,which severely limits the application of Ti O₂in the field of photocatalytic nitrogen fixation.How to effectively improve the separation efficiency of photogenerated carriers,promote the interface transfer of photogenerated electrons from the catalyst body to the adsorbed nitrogen on the surface,and broaden the solar energy absorption range of the catalyst is a hot topic of current research.Here,we use solvothermal and hydrogen annealing methods to prepare a titanate-Ti O₂low-dimensional heterostructure composite material on the surface of a metal titanium sheet.The composite material has a nanosheet layered structure and abundant body/surface defects,can significantly shorten the transmission distance of photogenerated electrons to the interface,and has good visible light absorption activity.On this basis,by recombining with metal Ru clusters,the photocatalyst has significantly enhanced photocatalytic nitrogen activation performance.Under room temperature visible light irradiation,the photocatalytic ammonia synthesis rate is as high as 1793μg g^-1h^-1.In addition,the composite material shows good long-term stability,and its photocatalytic performance is far superior to that of pure Ti O₂.On this basis,we assembled metal Pt nanoparticles on the surface of the lamellar titanate-Ti O₂composite material.Studies have found that during the hydrogen annealing process,the presence of metal Pt nanoparticles can promote the generation of a large number of surface oxygen vacancies in adjacent Ti O₂units,which serve as active sites for the adsorption and activation of N₂molecules.This unique Pt-V_O-Ti³⁺structure can effectively enhance the separation of electrons and holes,promote the transfer of photogenerated electrons from the semiconductor phase to the active center of oxygen vacancies,and then to the adsorption of nitrogen molecules,resulting in excellent visible light photocatalytic ammonia synthesis performance.Under room temperature visible light irradiation,the photocatalytic ammonia synthesis rate is as high as 1716μg g-1 h-1.