Study On The Preparation Of 1D G-C₃N₄ Photocatalytic Materials And Their Activity

Energy and environment are the two important problems facing the sustainable development of human society.Due to its inexhaustible,pollution-free,renewable and other advantages,solar energy will play an important role in the development of new energy in the future,and semiconductor photocatalysis technology refers to the use of photocatalysts to convert solar energy into chemical energy.Emerging technologies have received great attention from the international community.H₂O₂,as a green and environmentally friendly oxidant,has been widely used in our daily life and industrial production,and the low cost,safety,and environmental protection of semiconductor photocatalysis technology make it one of the most valuable methods for producing H₂O₂.Efficient photocatalysts for the production of H₂O₂ have epoch-making significance.At the same time,hydrogen energy has the advantages of high combustion value,and the combustion product is water without environmental pollution.Therefore,using the abundant solar energy in nature to produce hydrogen by photolysis of water is one of the ways of sustainable development,and it is currently a research hotspot using photocatalysis technology.In recent years,g-C₃N₄ has attracted much attention due to its stable chemical properties,environmental friendliness,and suitable energy band structure.However,some shortcomings including the fast recombination of photogenerated electron-hole pairs and small specific surface area in traditional 2D g-C₃N₄ seriously impede its photocatalytic performance for H₂O₂ production and photohydrolysis for hydrogen production.In this paper,two materials were synthesized by the morphology control of the pristine 2D g-C₃N₄ and the doping of potassium ions,and the g-C₃N₄ was modified to achieve efficient photocatalytic performance.Considering the disadvantages of 2D nanosheet g-C₃N₄,such as low carrier separation efficiency and small specific surface area,1D hollow nanostructures possess intriguing physicochemical properties and are adopted to overcome the intrinsic shortcomings of g-C₃N₄.Herein,g-C₃N₄ with hollow hexagonal prism（CN-HP）is successfully synthesized by hydrothermal treatment of melamine and then calcined at high temperature for photocatalytic production of H₂O₂.The reasons for the enhanced photocatalytic performance were analyzed through a series of characterizations.Compared with traditional 2D g-C₃N₄,the specific surface area of CN-HP increases to 41.513 m~2/g,exposing more active sites;Meanwhile,its hollow tubular structure can shorten the migration distance of photogenerated electrons to the catalyst surface,reduce the recombination probability of photogenerated electrons and holes,and prolong the lifetime of photogenerated electrons,thereby realizing efficient photocatalytic production of H₂O₂.The performance test data show that the yield of H₂O₂production reaches 4.08μmol over CN-HP in 40 min,which is about 7 times than that of traditional 2D g-C₃N₄.K-doped tubular carbon nitride（K10-TCN）with high photocatalytic hydrogen evolution activity was prepared by hydrothermal pretreatment with potassium iodide and dicyandiamide and high temperature calcination.The formation of microtubules promotes the increase of the specific surface area of K10-TCN to 35.04 m~2/g,compared with 8.37m~2/g for conventional 2D g-C₃N₄;the doping of potassium tunes the energy band structure,resulting in a narrower band gap and slightly enhanced light absorption;microtubule formation and potassium doping synergistically promote the enhanced photogenerated carrier separation efficiency,which in turn enhances the photocatalytic hydrogen evolution activity of g-C₃N₄.The photocatalytic hydrogen evolution performance test showed that the hydrogen evolution rate of K10-TCN in water reached 961.64μmol g^-1 h^-1,about 5.5 times that of conventional two-dimensional g-C₃N₄.The enhanced photocatalytic hydrogen evolution performance is attributed to potassium doping and the formation of 1D tubular structures.This research provides a valuable reference for the development of green materials for efficient photocatalytic production of H₂O₂ and photocatalytic H₂ evolution.