Study On The Preparation And Properties Of G-C₃N₄ Photocatalyst Anchored By Manganese Based Single Molecular Cluster

With the progress of human society,the traditional fossil fuel is gradually replaced by other new environmental protection energy.Among them,hydrogen energy has become one of the most promising new energy sources.A large amount of hydrogen can be produced by putting photocatalyst with suitable energy band structure into water under the irradiation of sunlight.In this process,the design and construction of a reasonable photocatalyst is the key factor to convert solar energy into chemical energy.The g-C₃N₄ is a kind of low-cost polymer semiconductor.It is considered to be one of the most promising photocatalytic materials because of its excellent stability,suitable energy band structure and simple preparation method.However,due to its small surface area,less light absorption,uncontrollable structure and high electron hole recombination rate,g-C₃N₄ has been limited its development.At present,various attempts have been made to improve the performance of g-C₃N₄.In this paper,Mn₁₂ single molecular cluster is selected as the research object.Compared with other common zero dimensional materials,Mn₁₂ has the advantages of small molecular size,simple preparation process,strong light absorption ability,weak interaction force,exchange reaction,oxidation of g-C₃N₄ as oxidant,etc.These advantages are beneficial to prevent the recombination of photogenerated electrons and holes and improve the photocatalytic performance of g-C₃N₄.Mn₁₂/g-C₃N₄ composite photocatalyst with excellent performance was obtained by simple liquid-phase method at room temperature combined with subsequent ultrasonic heating.In the crystal state,Mn₁₂ can't be compounded with g-C₃N₄.After the solution of acetonitrile and the ultrasonic heating in acetonitrile environment,there are many defects on the surface,and the inside is network like nano sheet structure.In a series of photocatalytic reactions,Mn₁₂ clusters are loaded on the surface of g-C₃N₄ to promote the absorption of light,and the photogenerated electrons migrate to the surface of Mn₁₂ rapidly,thus effectively inhibiting the recombination of photogenerated carriers.In addition,the hydrogen production rate of Mn₁₂/g-C₃N₄composite photocatalyst is much higher than that of pure g-C₃N₄.In order to enhance the interaction between Mn₁₂ and g-C₃N₄,the carboxyl exchange reaction of Mn₁₂ was used to anchor Mn₁₂ on the surface of g-C₃N₄ rich in carboxyl.The g-C₃N₄ was treated by concentrated sulfuric acid and concentrated nitric acid to obtain oxidized porous carbon nitrogen?POCNs?with carboxyl functional groups on its surface.Subsequently,Mn₁₂/POCNs photocatalyst was prepared by anchoring Mn₁₂ on POCNs through the carboxyl exchange reaction of Mn₁₂.Between Mn₁₂ and POCNs,Mn₁₂ can attract electrons from POCNs,leading to electron transfer.The electron migration resistance of the material is reduced,the photogenerated electron hole separation is fast,the carrier migration rate is increased,and the photocatalyst material has excellent photocatalytic activity and cycle stability.This work provides a new way to improve the performance of g-C₃N₄ from the aspects of material,electronic structure and carrier behavior regulation.