Preparation And Photocatalytic Properties Of Sulfur Contained Carbon Nitride Quantum Dots And Modified G-C₃N₄ Composites

g-C₃N₄has been widely used in the field of optoelectronic device,sensor,photocatalytic water splitting to produce hydrogen,and degradation of pollutants,due to its superior physical and chemical characteristics as well as the suitable band structure.However,g-C₃N₄still suffers from some deficiencies such as poor charge separation and transfer capability,low efficiency in visible light absorption and utilization,and few of reaction sites.To solve the problem of g-C₃N₄in photocatalytic application,we aimed to improve the photocatlytic activity of g-C₃N₄for the degradation of methyl orange?MO?under visible light by combining different modification methods in this paper.The specific contents are as follows:At first,g-C₃N₄was oxidized by strong acid?O-CN?,then sulfur contained carbon nitride quantum dots were loaded on the surface of oxidized g-C₃N₄?O-CN/SCNQDs?through solution refluxing.At the optimal doping ratio,the degradation rate of MO reached 1.43mg/?h.100mg catalyst?under visible-light irradiation,which was 4.46 times of g-C₃N₄?CN?and 1.98 times of the bulk g-C₃N₄modified by quantum dots?CN/SCNQDs?.Compared to the bulk g-C₃N₄,characterization results presented that quantum dots were more favorable to depose tightly on the surface of oxidized g-C₃N₄and the band structure would be adjusted in the oxidization process as well.Additionally,phosphorus doped g-C₃N₄?P-CN?was prepared through calcining the precursors,and the sulfur contained carbon nitride quantum dots were introduced as well?P-CN/SCNQDs?.The effect of the ratio of melamine and thiourea for quantum dots and composites was researched.The experimental results showed that the introduction of phosphorus could reduce the band gap and improve the charges separation efficiency,while quantum dots facilitated to enhance the absorption ability of light.The most favorable ratio for the synthesis of quantum dots was 1:1.The degradation rate for MO of composite materials was 1.59mg/?h.100mg catalyst?under visible light,which was 3.4 times of phosphorus-doped g-C₃N₄.