【作者】 张悦；

【导师】 刘鹏霄；

【作者基本信息】 中北大学 ， 环境工程， 2025， 硕士

【摘要】 作为一种绿色能源转化技术,半导体光催化通过太阳能的驱动可实现化学物质的高效转化,在应对全球能源短缺和环境污染治理方面具有显著的应用价值。石墨相氮化碳（g-C₃N₄）由于其带隙窄、可见光响应范围广等优点受到了广泛关注,但其光电转换效率低、光生电子-空穴易复合等问题严重限制了其光催化活性。在太阳能光催化过程中利用g-C₃N₄本征压电效应特性构建的内建电场,可以调节光生电荷的分离和转移路径,从而提升催化效率。本研究拟以g-C₃N₄为研究对象,利用光催化和压电催化协同效应,通过对其表面形貌和官能团结构调控提升材料的压电光催化活性,从而增强其有机污染物降解效能。本研究的具体工作如下:（1）开发提升压电光催化性能的多孔氮化碳并探究催化剂表面形貌变化对催化性能的影响。以NH₄Cl和三聚氰胺为前驱体,采用一步高温煅烧法制备不同形态结构的氮化碳,在此基础上,通过优化NH₄Cl用量,研究其在三维蜂窝状薄壁多孔结构g-C₃N₄形成过程中的影响,并研究其对压电光催化降解四环素（TC）性能的影响。研究发现,NH₄Cl可以显著改变氮化碳的形态和结构,其中三聚氰胺和NH₄Cl的配比为1:4时为最优结构（CN-4）,孔的比表面积是提高压电光催化降解抗生素污染物性能的关键因素。在300 W氙灯,λ>420 nm,超声65 k Hz,360W条件下,CN-4降解TC的速率常数为0.0343 min^-1,是不添加NH₄Cl的块状结构CN的3.2倍。压电力学显微镜测试结果表明调控孔结构有利于增强压电催化活性,结合自由基捕获实验证实反应过程的主要活性物质,并提出降解催化机制。最后,采用高效液相色谱-质谱联用技术（HPLC-MS）对降解过程的中间产物进行系统分析,进而推测四环素（TC）可能的降解途径,使用毒性分析软件（T.E.S.T）对其进行毒性评估,其中所有中间体的发育毒性均显著降低。（2）在氮化碳边缘枝接氰基以提高压电光催化降解抗生素效率并探究材料结构差异性对降解效果的影响。采用熔融盐法,引入硫氰化钾成功制备氰基改性氮化碳（CN-CA-0.5）。实验结果表明,在CN-4框架中引入氰基可以提高压电性,通过压电极化电荷增强了光生电子-空穴对的分离。同时在可见光照射和超声波作用下,CN-CA-0.5在反应90 min后对TC的降解达到89.6%,在15 min内显示出0.0929 min^-1的优异反应速率,是未引入氰基催化剂的2.71倍,表明氰基增强了氮化碳的不对称结构。通过自由基捕获和电子自旋共振谱（EPR）实验确定了·O₂^-是催化剂表面形成的活性氧物种（ROS）,由此提出压电光催化反应机理。最后,采用LC-MS对TC进行中间产物测定,推测其降解路径,并对TC产物的毒性进行评价。本研究通过结构调控优化石墨相氮化碳的能带结构和电荷分离效率,并创新性耦合压电效应,利用超声波振动诱导内建电场进一步抑制电子空穴对复合。该策略通过压电光催化协同机制实现了对抗生素的高效降解,为设计新型环境修复材料提供了理论依据和技术路径。更多还原

【Abstract】 Semiconductor photocatalytic technology enables efficient chemical conversion using clean and renewable solar energy,demonstrating significant application potential in addressing energy shortages and environmental pollution.Graphitic carbon nitride（g-C₃N₄）has attracted extensive attention due to its narrow bandgap and broad visible-light response range.However,its photocatalytic activity is severely constrained by low photoelectric conversion efficiency and rapid recombination of photogenerated electron-hole pairs.By leveraging the intrinsic piezoelectric effect of g-C₃N₄ to establish a built-in electric field during solar photocatalysis,the separation and transfer pathways of photogenerated charges can be regulated,thereby enhancing catalytic efficiency.This study focuses on g-C₃N₄,aiming to improve its piezophotocatalytic performance and organic pollutant degradation capability by modulating its surface morphology and functional group structures through the synergistic integration of photocatalysis and piezocatalysis.The research comprises the following components:（1）Development of porous carbon nitride with enhanced piezophotocatalytic performance and investigation of the influence of catalyst morphology on catalytic activity.Using NH₄Cl and melamine as precursors,carbon nitride with diverse morphologies was synthesized via a one-step high-temperature calcination method.By optimizing the NH₄Cl dosage,its role in forming three-dimensional honeycomb-like thin-walled porous g-C₃N₄ was examined,along with its impact on the piezophotocatalytic degradation of tetracycline（TC）.Results revealed that NH₄Cl significantly alters the morphology and structure of carbon nitride,with the optimal configuration（CN-4）achieved at a melamine-to-NH₄Cl ratio of 1:4.The specific surface area of the pores was identified as a critical factor in enhancing piezophotocatalytic antibiotic degradation.Under conditions of a 300 W xenon lamp（λ>420 nm）,65 k Hz ultrasound,and 360 W power,CN-4 exhibited a TC degradation rate constant of 0.0343min^-1,3.2 times higher than that of bulk-structured CN without NH₄Cl.Piezoresponse force microscopy（PFM）confirmed that pore structure modulation enhances piezocatalytic activity.Radical trapping experiments identified the primary active species involved in the reaction,leading to a proposed catalytic mechanism.Furthermore,liquid chromatography-mass spectrometry（LC-MS）was employed to analyze intermediate degradation products,elucidate potential TC degradation pathways,and evaluate their toxicity using the Toxicity Estimation Software Tool（T.E.S.T）.（2）Cyanogen functionalization at carbon nitride edges to boost piezophotocatalytic antibiotic degradation efficiency and exploration of material structural effects on degradation performance.Cyanogen-modified carbon nitride（CN-CA-0.5）was successfully synthesized via a molten salt thermal method using potassium thiocyanate.Experimental results demonstrated that introducing cyano groups into the CN-4framework enhances piezoelectricity,improving the separation of photogenerated electron-hole pairs through piezoelectric polarization charges.Under visible light irradiation and ultrasound,CN-CA-0.5 achieved 89.6%TC degradation within 90 min,with an exceptional reaction rate of 0.0929 min^-1in the initial 15 min—2.71 times higher than that of the unmodified catalyst—indicating that cyano groups reinforce the asymmetric structure of carbon nitride.Radical trapping and electron paramagnetic resonance（EPR）experiments identified·O₂^- as the dominant reactive oxygen species（ROS）generated on the catalyst surface,leading to a proposed piezophotocatalytic reaction mechanism.Finally,LC-MS was utilized to detect intermediate TC degradation products,infer degradation pathways,and assess the toxicity of resultant byproducts.This study optimizes the band structure and charge separation efficiency of graphitic carbon nitride through structural engineering and innovatively integrates the piezoelectric effect,utilizing ultrasound-induced built-in electric fields to further suppress electron-hole recombination.This synergistic piezophotocatalytic strategy achieves highly efficient antibiotic degradation,providing both theoretical insights and technical pathways for designing advanced environmental remediation materials.更多还原