Preparation And Performance Of Carbon Dots Doped Ternary Composite Catalyst

Photocatalysis is considered to be one of the important technical approaches that"can simultaneously solve energy and environmental problems."However,there are still great challenges in obtaining high-performance photocatalytic materials.Constructing a multi-element composite system has attracted much attention because it can improve the catalytic activity by gathering the advantages of each component.Therefore,how to design/build a composite system to maximize performance or develop new performance is the current research focus.Carbon dots?CDs?have unique advantages such as wide source of raw materials,simple preparation,excellent photophysical and photochemical properties,and have shown important application prospects in the field of photocatalysis.Copper metal and its compounds?such as copper oxide,etc.?are also considered as catalytic materials with good application potential due to their excellent light absorption capacity,high catalytic activity,and low cost.Therefore,in this paper,metallic copper or its compounds is introduced into the carbon dots composite structure,and two ternary composite systems with carbon dots doping are designed:carbon dots/copper oxide/mesoporous hydroxyapatite and carbon dots/copper/carbon nitride nanosheets has carried out systematic research on the synthesis,light absorption and conversion performance,catalytic mechanism of the composite structure.The main contents of this paper are as follows:First,the carbon dots solution was synthesized using citric acid as the raw material,and then combined carbon dots,copper nitrate solution and laboratory-made mesoporous hydroxyapatite to obtain carbon dots/copper oxide/mesoporous hydroxyapatite?CDs/CuO/mHA?under hydrothermal conditions.TEM,XRD,XPS and other results indicate that CDs/CuO/mHA composites were successfully prepared.The experiment of reducing p-nitrophenol?4-NP?showed that CDs/CuO/mHA has excellent catalytic activity under dark conditions.This is mainly due to?1?In the catalytic environment,CuO is reduced to Cu₂O and Cu,then Cu₂O and Cu are quickly oxidized to CuO in the aqueous solution.This reversible phase transformation greatly promotes electron transport and further promotes the reduction of p-nitrophenol?4-NP?,?2?The?-?*structure on the surface of CDs can enhance the adsorption of 4-NP,?3?mHA has high specific surface area and electron storage capacity,?4?There is a good interface bonding between the components.Secondly,we systematically analyzed the performance of the composite system to catalyze4-NP after the introduction of light,and discussed the effects of different light intensities,different wavelengths,and temperature changes caused by light intensity on catalytic performance.the result shows,as the light intensity increases,the catalytic rate increases,and as the wavelength increases,the catalytic reduction performance also increases,but the temperature change has no significant effect on the catalytic performance.In the light,on the one hand,photogenerated holes can promote the faster oxidation of Cu₂O and Cu to CuO,on the other hand,CDs play an electron donor role in the photocatalytic process.In addition,the catalytic activity of CDs/CuO/mHA decreased by less than 5%after 5 cycles of photocatalysis,which indicats that the composite has excellent reusability and structural stability.Finally,based on the unique properties of carbon nitride?g-C₃N₄?,we further designed a carbon dots/copper/carbon nitride nanosheets composite structure?CDs/Cu/g-C₃N₄?.Using melamine as the raw material,the bulk g-C₃N₄ was first prepared,and then the bulk g-C₃N₄was calcined in air to obtain g-C₃N₄ nanosheets.The photocatalytic performance of the composite structure was preliminary analyzed.The results show that the light absorption ability of the composite samples are enhanced,but these catalytic performance is not improved.We speculated that it may be that after multiple components are recombined,more defects are introduced and their catalytic activity is weakened.Further research work will be carried out in the future.