核壳异质结协同量子效应增强g-C3N4/TiO2可见-近红外光催化性能研究

Green, stable, and high quantum efficiency are important factors for environment photocatalysis. Combining the quantum effect with the heterojunction to improve the photocatalytic activity of g-C3N4/TiO2-based composites under the wide range spectrum irradiation is efficient and meaningful for environment protection. However, several issues need to be solved. (1) It’s hard to control the precision structure of g-C3N4 and its corresponding heterojunction, limiting the photocatalytic activity; (2) The band gap of g-C3N4 is enlarged because of the size effect. The absorption of visible light and NIR for photocatalysis is reduced, resulting in low quantum efficiency in practical application. According to the above points, we propose: (1) Employing the layer-by-layer technique to synthesize mesoporous g-C3N4@TiO2 core-shell heterojunction, and refine the structures and properties for visible light photocatalysis. (2) Synthesizing g-C3N4 quantum dots and investigating the relationships among their constitutions, structures, and properties. Then employ the g-C3N4 quantum dots to modify g-C3N4@TiO2 in order to further enhance the visible light and NIR photocatalytic activity. (3) Decomposing the tetracycline antibiotics by the as-prepared photocatalysts. The photocatalytic mechanisms and practical application potential will be discussed systematically through intermediate products and active radicles analysis. The present work is helpful to provide experimental and theoretical basis for improving the Vis-NIR photocatalytic efficiency.

针对环境光催化中绿色、稳定和高量子效率的要求，利用量子效应协同异质结增强g-C3N4/TiO2的宽光谱光催化活性具有重要意义。目前的研究还存在一些不足：（1）g-C3N4以及相应异质结的结构难以精确控制；（2）g-C3N4的尺寸效应导致其带隙增大，可见-近红外光能的吸收利用不足，实际应用的量子效率低。针对上述问题，本项目提出：（1）通过层层组装，合成可见光响应的介孔g-C3N4@TiO2核壳异质结光催化剂，并对其进行结构调节与性能优化。（2）可控合成g-C3N4量子点，系统研究其组成-结构-性能的关系，并利用其独特的性能增强g-C3N4@TiO2的可见-近红外光催化活性。（3）用合成的光催化材料来催化降解四环素类抗生素，从分子水平上分析光催化反应的中间产物和活性物质，阐明光催化机理与实际应用性能，为异质结、量子效应等协同增强可见-近红外光催化活性的研究提供实验和理论依据。

本项目以提高TiO2和g-C3N4光催化剂活性和机理研究为主要内容。首先，利用介孔SiO2为模板合成g-C3N4光催化剂，通过结构调控探讨量子尺寸效应、比表面积、吸收光谱等因素对光催化活性的影响。其次，通过构筑TiO2@C3N4和C3N4@TiO2异质结结构进一步探讨影响光催化活性的关键因素。再次，通过氮化碳量子点、碳量子点、三线态-三线态湮灭上转换功能材料等为功能物质，探讨光谱上转换和下转换导致的激发光子能量变化影响光催化活性的机制，并研究了表面等离子共振、肖特基结、晶面效应协同高能光子和低能光子影响TiO2光催化活性的机理。最后，以稻壳为代表性生物质探索了绿色光催化剂的合成与应用。大量实验结果表明，提升高能光子的比例和利用效率对协同异质结、表面等离子共振、肖特基结等效应提升光催化活性的作用具有积极影响。