Preparation Of G-C₃N₄ Composites And Their Photocatalytic Activity

In recent years,with the rapid development of global industrialization,the problem of energy shortage and ecological environmental pollution has become increasingly serious.As a kind of pollution-free,abundant and renewable energy,solar energy plays an extremely important role in the development of new energy in the future.Semiconductor photocatalysis technology has unique advantages in solving environmental pollution and energy shortage,especially in photodegradation of water pollution,reflecting the advantages of clean,efficient,and energy saving and so on.Graphite-phase g-C₃N₄ materials have attracted extensive attention due to its advantages of stable chemical properties,non-toxic,abundant raw materials and low cost.However,pure g-C₃N₄ materials have the disadvantages of low utilization rate of solar energy,small specific surface area and high composite rate of photogenic carriers,resulting in low photocatalysis.Therefore,the construction of efficient g-C₃N₄ based photocatalysts has become one of the hot topics in condensed matter physics.In this paper,homogeneous and heterogeneous g-C₃N₄-based heterogeneous junctions were designed and constructed based on energy band engineering,and efficient g-C₃N₄-based composite photocatalyst was obtained in response to visible light.The relationship between preparation process,morphology,composition,and structure and photocatalytic performance was systematically studied.This work provides a direction for the preparation of Z-type composite photocatalyst with high catalytic performance.The main research contents of this paper are as follows:?1?based on the band theory of solids,and through the ba nd position control,the preparation of CeO₂/g-C₃N₄ Z-type heterojunction structure,and compound semiconductor two types?classes and Z-type heterojunction photocatalytic mechanism has carried on the detailed research,confirm Z-type heterojunction build can effectively improve the optical carrier separation and transfer and prolong the life of light with carrier,greatly improving the photocatalytic performance.Studies have shown that the prepared CeO₂/g-C₃N₄ composite has a fusiform flower structure and a large specific surface area?102m²/g?,providing more active sit es for photocatalytic reactions.The degradation rate of CeO₂/g-C₃N₄ heteropaired MB(0.246h^-1)was4.8,8.8 and 30.8 times that of commercial P25(0.051 h^-1),massive g-C₃N₄(0.028 h^-1)and CeO₂(0.008 h^-1),respectively.?2?g-C₃N₄ prepared from different raw materials has different energy band structures,and the supramolecular precursor is formed by the hydrogen bond between melamine,cyanic acid and thiourea,and then the g-C₃N₄/g-C₃N₄ homogenous heterostructure is prepared by calcining the supramolecular precursor at high temperature.By analyzing the energy band structure of g-C₃N₄/g-C₃N₄ composite material,it is confirmed that the interface of homogeneous g-C₃N₄/g-C₃N₄ is a Z-type heterojunction,and in the photocatalytic process,the electrons on the more negative conduction band?CN-T CB?and the holes on the corrected valence band?CN-MC VB?are used as photogenic carriers to participate in the redox reaction.The Z-shaped heterojunction not only effectively separates electron-hole pairs,but also significantly improves the electron-hole redox ability.The results showed that g-C₃N₄/g-C₃N₄homogeneity heterojunction had a unique two-dimensional lamellar structure,a large specific surface area?60.9m²/g?,and the degradation efficiency of RhB under visible light irradiation was 0.833h^-1,which was 15.4 times of that of common g-C₃N₄.This study provides a simple method for the design of novel Z-type photocatalysts with specific morpho logies and the efficient catalytic degradation of organic pollutants by sunlight.