【作者】 李梅；

【导师】 王华； 刘红光；

【作者基本信息】 天津大学 ， 化学工程， 2018， 硕士

【摘要】 面向光催化分解水产氢及光催化还原CO₂的高效光催化剂的研究,对于开发可再生清洁能源与有效解决环境污染问题具有重要意义。类石墨半导体氮化碳是一种新型可见光驱动光催化材料,由于其高的物理化学稳定性、独特电子能带结构（2.7 eV）,在光催化领域有着重要应用。本文通过硬模板法制备类石墨氮化碳纳米棒/纳米球,研究其光催化产氢性能;并对纳米球进行表面Pt修饰,研究其光催化还原CO₂性能。以亚苯基桥连有机氧化硅纳米管为模板,氰胺为前驱体制备氮化碳纳米棒。确定了适宜的模板与前驱体比例,聚合温度等制备条件,得到了直径约6 nm,长度约50 nm的均匀分散氮化碳纳米棒PCN-BSNT_1/2-550。元素分析结果表明,PCN-BSNT_1/2-550中C/N值高于理想g-C₃N₄,是由于模板中的亚苯基高温碳化沉积于纳米棒表面。稳态荧光等表征表明PCN-BSNT_1/2-550纳米棒的电子-空穴分离、转移性能显著提高。在光催化分解水产氢和甲基橙降解反应中,具有较高比表面积及C-氮化碳异质结的PCN-BSNT_1/2-550显示出高催化活性,5 h内平均产氢速率可达73μmol·h^-1,甲基橙降解速率常数达到1.52·h^-1。以直径约20 nm的中空SiO₂纳米球为模板,氰胺为前驱体,通过调节SiO₂与氰胺质量比,得到直径约20 nm具有核-壳结构的氮化碳纳米球。表征结果表明,氮化碳纳米球的比表面积显著提高（112 m²/g）,其感光范围拓宽至550 nm。用于光催化分解水产氢和甲基橙降解,4 h内平均产氢速率达到174μmol·h^-1,甲基橙降解速率常数高达1.74·h^-1。结果表明氮化碳纳米球的超小尺寸,缩短了光生载流子由体相到表面的转移路径,促进了光生载流子的分离与转移,提高了其光催化性能。将制备的氮化碳纳米球进行表面Pt修饰,得到Pt/CNS复合光催化剂。TEM图显示3-5 nm Pt颗粒均匀分布于氮化碳纳米球表面,UV-vis表明Pt修饰的纳米球的感光范围拓宽,可见光吸收强度提高。结果表明,3Pt/CNS具有优异的光催化还原CO₂制CH₄性能,CH₄生成速率可达2.11μmol·g^-1_catalyst·h^-1。更多还原

【Abstract】 The research of high-efficency photocatalyst,which is applied for photocatalytic evolution of H₂ splitting from H₂O and reduction of CO₂,is of great significance for the development of renewable energy and effective solution of environmental pollution.Graphitic carbon nitride,a semiconductor is a new type of visible light-driven photocatalytic material.Graphitic carbon nitride has great potential in the field of photocatalysis due to its excellent physicochemistry stability and unique electronic strcture（2.7 eV）.In this thesis,graphitic carbon nitride nanorod/nanosphere were prepared by hard template method,and their photocatalytic hydrogen evolution performance was studied.The carbon nitride nanospheres were modified with Pt and their photocatalytic reduction of CO₂ performance was also studied.The carbon nitride nanorods were successfully prepared by using phenylene bridged organosilica nanotubes and cyanamide as template and precursor molecules,respectively.The experiments determine the appropriate ratio of template to precursor,the polymerization temperature and other preparation conditions,and obtain the uniform carbon nitride nanorods(PCN-BSNT_1/2-550)of about 6 nm in diameter and about 50 nm in length.The elemental analysis results showed that the C/N value of PCN-BSNT_1/2-550 is higher than that of ideal g-C₃N₄,which is due to the carbonization of phenylene in the template deposited on the surface of carbon nitride nanorods.UV-vis indicateed that the electron-hole separation and electron transfer properties of PCN-BSNT_1/2-550 were significantly improved.The PCN-BSNT_1/2-550with higher specific surface area and C-carbon nitride heterojunction showed high photocatalytic activity in the photocatalytic hydrogen evolution from water and degradation of methyl orange.The average hydrogen production rate within 5 h reached 73μmol·h^-1,the rate constant of methyl orange degradation reached reached1.52·h^-1.Carbon nitride nanospheres（d≈20 nm）with core-shell structure were prepared by adjusting the mass ratio of SiO₂ to cyanamide.The characterization results showed that the specific surface area of the carbon nitride nanospheres was significantly increased（112 m²/g）and the photosensitivity range is broadened to 550 nm.For the photocatalytic hrdrogen evolution and degradation of methyl orange,the rate of average hydrogen production reached 174μmol·h^-1 in 4 h,and the rate constant of methyl orange degradation reached 1.74 h^-1.The results showed that the ultra-small diameter of carbon nitride nanospheres shorten the transmission path of photoelectrons from the bulk phase to the surface,promoted the separation and transfer of photogenerated carriers,and improved its photocatalytic performance.The modification on the surface of carbon nitride nanospheres with Pt was performed to obtain the Pt/CNS composite photocatalyst.TEM images showed that the Pt nanoparticles with 3-5 nm in diameter were uniformly modified on the surface of the carbon nitride nanospheres.UV-vis characterization showed that the photoresponse range of 3Pt/CNS was broadened and the intensity of visible-light absorption is improved.The results show that 3Pt/CNS has excellent photocatalytic activity for the reduction of CO₂ to CH₄,and the rate of CH₄ generation is up to 2.11μmol·g^-1 catalyst·h^-1.更多还原