Preparation Of Graphite-like Carbon Nitride Composite Structure And Its Photocatalytic Activity

The rapid development of social economy has brought great pressure to the environment and caused tremendous pollution.Photocatalytic technology has great potential in environmental purification,which is one of the current research hotspots.Graphite-like carbon nitride?g-C₃N₄?,as a star material in photocatalytic field in recent years,has attracted much attention due to its advantages such as simple preparation method,visible light absorption,wide source,low price,good thermal stability and chemical stability.However,g-C₃N₄ also has some shortcomings such as small specific surface area and low efficiency of photoelectric separation.To solve the above problems,we proposed to construct g-C₃N₄ composite materials to adjust its surface properties,increase photoelectric separation,and synergistically improve its performance in photocatalytic degradation of organic pollutants in water.The following two aspects are studied and some meaningful results are obtained:?1?TiO₂/Na-g-C₃N₄ composites were prepared by recrystallization-annealing method.Following this method,TiO₂ can be uniformly dispersed into Na-g-C₃N₄ by recrystallization and high specific surface area can be obtained by salt decomposition and washing.TiO₂/Na-g-C₃N₄ was used for the photocatalytic degradation of organic pollutant methylene blue?MB?.It shows that the composite can adsorb MB rapidly and further degrade MB by photocatalysis,which has certain stability.The promotion mechanism is that the doping of Na makes the sample alkaline and negatively charged,thus increases the electrostatic adsorption of MB.Meanwhile,the introduced TiO₂ increased the surface area and promoted the photoelectric separation effect.?2?Ag-based bimetallic core-shell structure Ag-X/g-C₃N₄ was successfully prepared through photodeposition.The microstructures and optical properties of the samples with different bimetallic X?Pd,Au and Pt? were systematically studied.The effects of light,pH and loading conditions on the microstructures of core-shell structures were investigated.The mechanism of the formation of core-shell structures was analyzed and proposed.The transfer of photogenerated electrons from g-C₃N₄ to Ag nanoparticles with weak plasmon effect could effectively inhibit the photochemistry displacement of Ag species.However,for Ag nanoparticles with strong plasmon effect,the inversion of Ag to g-C₃N₄ by photogenerated electrons causes the Ag nanoparticles to be more easily oxidized and electrochemically displaced.The photocatalytic activity of Ag-Pd/g-C₃N₄ samples was greatly improved after the formation of core-shell structure.Ag-Pt/g-C₃N₄ and Ag-Pd/g-C₃N₄ show the best activity in MB degradation and hydrogen production,respectively.In summary,this paper has demonstrated the remarkable promotional effect on surface area improvement,surface property adjustment and photoelectric separation by combining g-C₃N₄ with other materials.The developed preparation method is simple,green and controllable,which provides a new idea for the development of highly efficient g-C₃N₄ photocatalyst.