Controllable Preparation Of Carbon Nitride Nanorods/nanospheres And The Study Of Photocatalytic Performance

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 73?mol·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 174?mol·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 2.11?mol·g^-1 catalyst·h^-1.