Synthesis And Properties Of G-C₃N₄/TiO₂ Composite Photocatalysts

With the development of industrialization,energy needs is increasing,what follows is the excessive exploitation of fossil energy and the increasing pollution of the environment.It is urgent for people to seek alternative energy and alleviate environmental pollution.As a mature new energy,hydrogen has the advantages of high calorific value,non-toxic and pollution-free.So it has been widely recognized.At present,the production methods of hydrogen are mainly concentrated in catalytic conversion of fossil fuels to produce hydrogen,Electrochemical water splitting.But these reactions consume more energy than they produce,resulting in a huge waste of energy.Photocatalytic water splitting is the cleanest method for hydrogen production,as the process requires only water as raw material.So photocatalysis technology has gained great research interest due to its potential applications in hydrogen energy production and decomposition of organic dyes.Herein,we utilize the simple hydrothermal method,by using the energy band difference between g-C₃N₄ and TiO₂ to construct composite photocatalysts with by regulating the raw materials,molar ratio,morphology.By combining step calcining to obtain nanotube g-C₃N₄.The Z-scheme nanotube g-C₃N₄/TiO₂ composite photocatalysts were successfully synthesized.By using synergistic protonation to obtain g-CNQD.The Z-scheme g-CNQDs/Ag/TiO₂ composite photocatalytics were synthesized.By using etching agent method to high crystallinity g-C₃N₄?CN-E?.The visible-light response Z-scheme g-C₃N₄/TiO₂ composite photocatalysis were synthesized.The obtained composite photocatalysis were characterized and the photocatalytic hydrogen and the degradation of RhB performance of the catalyst was investigated.The possible photocatalytic mechanism was explored by relevant experiments.Specifically,the work is carried out from the following three aspects.?1?Urea was used as precursor to prepare nanotube g-C₃N₄ by step calcining,enhancing the active site of the reaction.Then TiCl₄ was used as the Ti source was grown in situ on the surface of carbon nitride nanotubes to improve the efficient separation of electron holes.At last the Z-scheme nanotube g-C₃N₄/TiO₂ composite photocatalyst was prepared.The effects of TiO₂ with different contents on the photocatalytic hydrogen and the degradation of RhB performance of g-C₃N₄/TiO₂ were investigated experimentally.The results indicate that Z-scheme nanotube g-C₃N₄/TiO₂ composite photocatalyst by adding 20%TiO₂ the photocatalytic activity was the highest.Finally,the photocatalytic mechanism of the reaction was determined by using the capture experiment of·OH with TA,combined with PL,Mott-Schottky and UV-Vis proved to be Z-scheme.The method also provides an idea for the preparation of nanotube anatase-rutile biphasi g-C₃N₄/TiO₂.?2?The system combines the advantages of high electron utilization of g-CNQD and Ag loading on material can serve as trapping and conducting sites for electrons constructed Z-scheme g-CNQDs/Ag/TiO₂ microspheres composite photocatalyst.It maximizes the redox capacity of the catalyst and accelerates the separation of electrons and holes.The photocatalytic efficiency of TiO₂ have obviously improved.The effects of g-CNQDs with different contents on the photocatalytic hydrogen and the degradation of RhB performance of g-CNQDs/Ag/TiO₂ were investigated experimentally.The results indicate that the Z-scheme g-CNQDs/Ag/TiO₂ composite photocatalyst by adding 5%g-CNQDs have the highest photocatalytic activities and the hydrogen production efficiency reached 1471.68?mol/?g.h?and RhB?10ppm?can be almost completely degraded within 1h.Finally,the photocatalytic mechanism proved to be Z-scheme with Ag as the conductor.?3?In order to solve the problem of low crystallinity of carbon nitride caused by incomplete thermal polymerization process,using etching to obtain CN-E with high crystallinity then loaded on the TiO₂ to prepared Z-scheme g-C₃N₄/TiO₂ composite photocatalysts.The effects of CN-E with different contents on the visible light hydrogen and the degradation of RhB performance of g-C₃N₄/TiO₂ were investigated experimentally.The results showed that when the mass ratio of CN-E was 60mg the photocatalytic activity was the highest and the visible light hydrogen production efficiency reached 170?mol·g^-1·h^-11 and RhB?10ppm?can be almost completely degraded within 1h.Finally,the photocatalytic mechanism of the reaction was determined by using the capture experiment of·OH with TA,combined with PL,Mott-Schottky and UV-Vis proved to be Z-scheme.